Electronics Circuit And Devices.docx

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Electronics Circuit and Devices

Viva Questions: Q1) Distinguish between Intrinsic and extrinsic Semiconductor ? Ans: Intrinsic Semiconductor: 1) These are the crystals of pure elements like germanium and silicon. 2) The number density of electrons is equal to the number density of holes. 3) The electrical conductivity is low. 4) Electrical conductivity depends on temperature. Extrinsic Semiconductor: 1) Impurity are added. 2) Number density of electrons are not equal to the density of holes. 3) Electrical conductivity is high. 4) Electrical conductivity depends on temperature as well as amount of impurity added. Q2) Define Hall Effect ? Ans: Hall effect is the potential difference across a electrical conductor when a magnetic field is applied in a direction perpendicular to that of the flow of current. Q3) Main Difference of unipolar and bipolar transistors ? Ans: Bipolar transistors can have both minority and majority carriers flowing, whereas unipolar have only majority carriers. BJT transistor is Bipolar and MOSFET,JFET are unipolar. You can find mor elaborated detailed notes on BJT here.Switches in Electronics Q4) Differentiate pinch off voltage and cut off voltage ? Ans: Pinch of voltage: It is the minimum drain-source voltage at which the drain current essentially becomes constant. Cut off voltage: It is the gate source voltage where the channel completely cut off and the drain current becomes zero. Q5) What is Tunnel Diode ? Ans: Answer for this question is explained in this post. Diodes and its Application Applications of tunnel diode are: High speed switching circuits and in logic circuits. Q6) Difference between Avalanche Breakdown and Zener Breakdown ? Ans:

Q7) In which region BJT acts as an Amplifier ? Ans: In active region BJT acts as an amplifier. Q8) Advantages of CE configuration over CB and CC ? Ans:

CE

Medium Rin High Rout High Voltage gain High Current gain

CB

CC

Low Rin High Rout High Volatge gain Current gain 0.99

High Rin Low Rout Voltage gain 0.99 Medium current gain

Q9) Explain Early Effect ? Ans: Early effect is the variation in the width of the base in BJT due to variation in applied base to collector voltage. Q10) Advantage of Full wave Rectifier over Half wave Rectifier ? Ans: 1) Full wave rectifier efficiency is double that of half wave. 2) Ripple voltage is low and of higher frequency for full wave rectifier. 3) Higher output voltage,higher output power and higher transformation utilization factor for full wave rectifier. 4) No problem due to dc saturation of core. Question No. 01: What is modulation? Answer: Modulation is the process of varying some characteristic of a periodic wave with an external signal. Radio communication superimposes this information bearing signal onto a carrier signal. These high frequency carrier signals can be transmitted over the air easily and are capable of traveling long distances. The characteristics (amplitude, frequency, or phase) of the carrier signal are varied in accordance with the information bearing signal. Modulation is utilized to send an information bearing signal over long distances. Question No. 02: What is resistor? Answer: A resistor is a two-terminal electronic component that opposes an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm’s law: V = IR. Question No. 03: What is an Amplifier? Answer: Amplifier is an electronic device or electrical circuit that is used to boost (amplify) the power, voltage or current of an applied signal. Question No. 04: What is inductor? Answer: An inductor is a passive electrical device employed in electrical circuits for its property of inductance. An inductor can take many forms. Question No. 05: What is op-amp? Answer: An operational amplifier, often called an op-amp, is a DC-coupled high-gain electronic voltage amplifier with differential inputs [1] and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of its output voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation. Question No. 06: What is demodulation? Answer: Demodulation is the act of removing the modulation from an analog signal to get the original baseband signal back. Demodulating is necessary because the receiver system receives a modulated signal with specific characteristics and it needs to turn it to baseband. Question No. 07: What is meant by impedance diagram?

Answer: The equivalent circuit of all the components of the power system are drawn and they are interconnected is called impedance diagram. Question No. 08: What is the need for base values? Answer: The components of power system may operate at different voltage and power levels. It will be convenient for analysis of power system if the voltage, power, current ratings of the components of the power system is expressed with reference to a common value called base value. Question No. 09: Explain AM and FM? Answer: AM-Amplitude modulation is a type of modulation where the amplitude of the carrier signal is varied in accordance with the information bearing signal. FM-Frequency modulation is a type of modulation where the frequency of the carrier signal is varied in accordance with the information bearing signal. Question No. 10: What is Electronic? Answer: The study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles is called Electronic. Question No. 11: What is transistor? Answer: In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. The transistor is the fundamental building block of computers, and all other modern electronic devices. Some transistors are packaged individually but most are found in integrated circuits. Question No. 12: What are CDMA, TDMA, and FDMA? Answer: Code division multiple access (CDMA) is a channel access method utilized by various radio communication technologies. CDMA employs spread spectrum technology and a special coding scheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same physical channel. By contrast, time division multiple access (TDMA) divides access by time, while frequency division multiple access (FDMA) divides it by frequency. An analogy to the problem of multiple access is a room (channel) in which people wish to communicate with each other. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division). In CDMA, they would speak different languages. People speaking the same language can understand each other, but not other people. Question No. 13: What is the need for load flow study? Answer: The load flow study of a power system is essential to decide the best operation existing system and for planning the future expansion of the system. It is also essential for designing the power system. Question No. 14: Advantages of negative feedback over positive feedback? Answer: Much attention has been given by researchers to negative feedback processes, because negative feedback processes lead systems towards equilibrium states. Positive feedback reinforces a given tendency of a system and can lead a system away from equilibrium states, possibly causing quite unexpected results. Question No. 15: What is communication?

Answer: Communication means transferring a signal from the transmitter which passes through a medium then the output is obtained at the receiver or communication says as transferring of message from one place to another place called communication. Question No. 16: What is pass band? Answer: Pass band is the range of frequencies or wavelengths that can pass through a filter without being attenuated. Question No. 17: Explain RF? Answer: Radio frequency (RF) is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves. Since most of this range is beyond the vibration rate that most mechanical systems can respond to, RF usually refers to oscillations in electrical circuits or electromagnetic radiation. Question No. 18: What is Instrumentation Amplifier (IA) and what are all the advantages? Answer: An instrumentation amplifier is a differential op-amp circuit providing high input impedances with ease of gain adjustment by varying a single resistor. Question No. 19: What is a semi conductor? Answer: A semiconductor is a solid material that has electrical conductivity in between that of a conductor and that of an insulator (An Insulator is a material that resists the flow of electric current. It is an object intended to support or separate electrical conductors without passing current through itself); It can vary over that wide range either permanently or dynamically. Question No. 20: What is sampling? Answer: The process of obtaining a set of samples from a continuous function of time x(t) is referred to as sampling. Question No. 21: Different types of communications? Answer: Types of communications are Analog and digital communication. Analog communication: As a technology, analog is the process of taking an audio or video signal (the human voice) and translating it into electronic pulses. Digital on the other hand is breaking the signal into a binary format where the audio or video data is represented by a series of “1”s and “0”s. Digital communication: Digital signals are immune to noise, quality of transmission and reception is good, components used in digital communication can be produced with high precision and power consumption is also very less when compared with analog signals. Question No. 22: What is a base station? Answer: Base station is a radio receiver/transmitter that serves as the hub of the local wireless network, and may also be the gateway between a wired network and the wireless network. Question No. 23: What are the main divisions of power system? Answer: The generating system, transmission system, and distribution system. Question No. 24: What is Barkhausen criterion? Answer: Barkhausen criteria, without which you will not know which conditions, are to be satisfied for oscillations.

“Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product of the transfer gain of the amplifier and the magnitude of the feedback factor of the feedback network (the magnitude of the loop gain) are less than unity”. The condition of unity loop gain - Aβ = 1 is called the Barkhausen criterion. This condition implies that Aβ = 1 and that the phase of - Aβ is zero. Question No. 25: Example for positive feedback and negative feedback? Answer: Example for +ve feedback is Oscillators and for -ve feedback is Amplifiers. Question No. 26: State ‘Sampling Theorem’? Answer: It states that, while taking the samples of a continuous signal, it has to be taken care that the sampling rate is equal to or greater than twice the cut off frequency and the minimum sampling rate is known as the Nyquist rate. Question No. 27: How many satellites are required to cover the earth? Answer: 3 satellites are required to cover the entire earth, which is placed at 120 degree to each other. The life span of the satellite is about 15 years. Question No. 28: Explain different types of feedback? Answer: Types of feedback are: Negative feedback: This tends to reduce output (but in amplifiers, stabilizes and linearizes operation). Negative feedback feeds part of a system’s output, inverted, into the system’s input; Generally with the result those fluctuations are attenuated. Positive feedback: This tends to increase output. Positive feedback, sometimes referred to as “cumulative causation”, is a feedback loop system in which the system responds to perturbation (A perturbation means a system, is an alteration of function, induced by external or internal mechanisms) in the same direction as the perturbation. In contrast, a system that responds to the perturbation in the opposite direction is called a negative feedback system. Bipolar feedback: which can either increase or decrease output. Question No. 29: Where do we use AM and FM? Answer: AM is used for video signals for example TV. Ranges from 535 to 1705 kHz FM is used for audio signals for example Radio. Ranges from 88 to 108 MHz Question No. 30: What is stop band? Answer: A stop-band is a band of frequencies, between specified limits, in which a circuit, such as a filter or telephone circuit, does not let signals through, or the attenuation is above the required stop-band attenuation level. Question No. 31: What is Oscillator? Answer: An oscillator is a circuit that creates a waveform output from a direct current input. The two main types of oscillator are harmonic and relaxation. The harmonic oscillators have smooth curved waveforms, while relaxation oscillators have waveforms with sharp changes. Question No. 32: What is conductor? Answer: A substance, body, or device that readily conducts heat, electricity, sound, etc. Copper is a good conductor of electricity.

Question No. 33: What is a repeater? Answer: A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation. Question No. 34: What is cut-off frequency? Answer: The frequency at which the response is -3dB with respect to the maximum response. Question No. 35: What is diode? Answer: In electronics, a diode is a two-terminal device. Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional current property. Question No. 36: Name the modulation techniques? Answer: For Analog modulation–AM, SSB, FM, PM and SM Digital modulation–OOK, FSK, ASK, PSK, QAM, MSK, CPM, PPM, TCM, OFDM Question No. 37: What is a feedback? Answer: Feedback is a process whereby some proportion of the output signal of a system is passed (fed back) to the input. This is often used to control the dynamic behavior of the system. Question No. 38: What is crosstalk? Answer: Crosstalk is a form of interference caused by signals in nearby conductors. The most common example is hearing an unwanted conversation on the telephone. Crosstalk can also occur in radios, televisions, networking equipment, and even electric guitars. Question No. 39: What is an Integrated Circuit? Answer: An integrated circuit (IC), also called a microchip, is an electronic circuit etched onto a silicon chip. Their main advantages are low cost, low power, high performance, and very small size.

1. What is the difference b/w Electronics and Electrical? Electronics is the science which deals with the currents in semiconductor materials, Vacuum tubes.Where electrical deals with the currents in conductors 2.What are types of materials? conductors (Energy gap is zero) semiconductors (Energy gap is narrower) (si 1.1ev,ge 0.7ev) Insulators (energy gap is widest). 3.What are the Semiconductor and conductors? Semiconductor which has 4 electrons in its valance band, and conductors has more than 4 electrons its valance band (best conductors: Ag,Al,Cu) 4. Difference b/w intrinsic and extrinsic Semiconductors?

Ans: intrinsic semiconductors are pure semiconductors, Extrinsic are impure, i.e.by adding impurities (tri, pentavalent)Extrinsic semiconductors created(P,N Type). 5.What are the type in Extrinsic semiconductors and how the formed? P-Type and N-Type by adding trivalentimpurities (arsenic, antimony, phosphorus) P-Type semiconductors created.by adding pentavalent impurities (aluminum, boron) N-Type semiconductors created. 6.What is Doping? The processes of adding impurities. 7.How the PN Junction will be formed? In a piece of semiconductor material, if one half is doped by P type impurity and the other half is doped by N type impurity 8.What is Barrier Potential (cut in voltage)? The forward voltage at which the current through the junction starts increasing rapidly 9.What is Forward bias and Reverse bias? In diode’s anode(P) voltage is more than cathode(N) voltage its forward bias, if anode voltage is less than cathode voltage its reverse bias. 10.What is Diffusion and Drift currents? Drift current depends on the electric field applied, if there is no electric field there is no drift current. Diffusion current occurs even though there is not an electric field applied to the semiconductor. 11.What is mean by 1n4007? 1n – single junction 400x-is indicates the voltage, current and power 4007 reverse voltage from 50v to 1000v, max forward current is 1A 12.What is the Diode current Equation? I=Io(e(V/nVT)-1), Io-Reverse saturation current,n=1,ge,2 si 13.Define PIV(Peak inverse voltage)? It is the maximum reverse voltage that can be applied to the Diode. if the voltage across the junction exceeds PIV, under reverse bias condition, the junction gets damaged. 14.Define Reverse saturation current? It is the current due to the diffusive flow of minority electrons from p- side to N- side, and minority holes from N- side to P- side 15.How do we test a diode using a multimeter? Connect anode of dide to + terminal of multimeter and cathode to Negative terminal if voltage is 0.3 to 0.7 then diode is good. 16.Explain the capacitive effects in a junction.

Diffusion capacitance occurs in Forward bias, Transition capacitance exist in Reverse Bias. 17.What is mean by Break down, difference b/w avalanche Break down and Zener Break down? Avalanche breakdown occurs in PN diode due to impact ionization of electron-hole pair, zener braek down occurs in Zener dioade due to electron hole pair break due to reverse bias voltage 18.What is the temperature effect on reverse saturation current and barrier voltage? Reverse saturation doubles for every 10 degrees increment in temperature Barrier voltage decreases by 2.5mv for every 1 degree increment in temperature 19.What is mean by static and dynamic resistances? Static resistance is the ratio of V,I at operating (Q) point, dynamic resistance is inverse to the slope of the forward bias characteristics curve at operating point. 20.What are the PN Diode, Zener diode applications? PN:rectifier,switch,clipper,clapper Zener Diode:voltage regulator 21.Difference b/w PN, Zener Diode? Pn is lightly doped, Zener heavily doped 22.Why is a Zener diode generally not connected in forward bias? Zener gives the same response as pn diode in forward bias, so it uses in reverse bias only with Zener break down 23.What is the effect of Temperature on Zener diode? For Vz(Break down voltage) less than 6v Vz is inversely proportional to temperature,For Vz(Break down voltage) more than 6v Vz is directly proportional to temperature. 24. Why silicon is more preferred than germanium? For Si break Down voltage Is more than Ge, reverse saturation current Is less in Si, Si is cheap (raw material Is sand) 1.What is the difference b/w AC and DC supply, what are the advantages of each? Ac supply is sinusoidal function of t, but Dc supply is constant for every time, dc can be storable but not Ac, Ac can transfer for a long distance but not Dc. 2.What is meant by regulation? Why is it required? It is a measure change in the magnitude between the sending and receiving end of a component.

3.How to convert AC to DC? Step down Transformer – Rectifier – Filter -- Regulator 4.What are the requirements of Linear mode power supply? Should give minimum operable DC voltage at rated current, ripples should low, should have short circuit protection, over voltage protection, should independent of temparature changes 5.What is transformer and types? Transformer works based on Induction Principle, when Two coils are placed nearly then voltage transfer exist, Types: Step down, step up Transformer 6.What is rectifier, filter, regulators? Rectifier coverts AC to pulsating DC Filter coverts the pulsating DC to Fluctuating DC Regulator convers fluctuating DC to exat DC 7.What are the various types in rectifiers and which one is best and why? Half, Full wave , Bridge Rectifier. Bridge rectifier is best because PIV is less, efficiency more, ripple factor less, TUF is more, peak facor less, transformer cost is less. 8.Define ripple factor, efficiency, transformer utilization factor, form factor, peak factors? Ripple factor= RMS value of ac component/Average value Efficiency= dc output power / ac input power TUF= dc power delivered to load/ac rating of transformer secondary Form factor=rms/ average Peak factor= peak value/ rms value 9.Define average value, RMS value, what is the significance of each? Average is defined as sum per count, i.e mean. Or area of one cycle per time period RMS is Root of Mean(average) of squares. If data contains Both +,_ signs then average value can not give perfect idea about it, then Rms value gives idea about data. 10.Compare all rectifiers?

11.Explain the importance of ripple and regulation in the case of a rectifier. Ripple factor gives the idea about fluctuations in signal, if it is less means ripples are less for DC ripple factor is Zero. Regulation gives idea about the variation of DC output voltage as a function of DC load current % regulation =(VNL-VFL)/VFL X 100% [ideal power supply its 0] 12.Explain why only the inductor or the capacitor alone is not used as filters to a FWR circuit. In inductor filter Ripple factor is inversely proportional to load, In capacitor filter Ripple factor is proportional to load, so in LC filter ripple factor will be independent of load. 13.What are the different filters used in AC to DC converters? Which is best and why? L,C,LC(L-section), π-section, RC filters. Best one is L-section because ripple factor is independent of load 14.Compare different filters?

15.Define line regulation and load regulation? Line reg= change in output voltage/ change in input voltage Load reg= (no load voltage- full load voltage)/ no load voltage 16.Define knee current? It is the minimum amount of voltage which is required to operate Diode 17.Define knee current? It is the minimum current through Zener diode in reverse bias

18.What are the different types of voltage regulators and which type is best, why?Zener diode voltage regulator, LM723, transistorized series and shunt regulators, best one is LM723 bcz its adjustable, short circuit protected, overvoltage protected 1.What is a transistor? A junction transistor is simply a sandwich of one type of semiconductor material between two layers of the other type. A transistor is a three terminal current sensing device. It can be looked upon as two pn junction placed back to back. The three terminals are named as emitter base & collector. 2.What is BJT, explain about its terminals, what are types, and which type is better, why? Bipolar junction Transistor in this corrent flows due to two polarities(electrons, holes), NPN or PNP type ,NPN is best because mobility of electrons is more than mobility of holes so electron current is more. 3.What are the different configurations of transistor? a) Common Emitter (CE) b) Common Base (CB) c) Common collector (CC) 4.What is Common Base configuration? base is common between input and output circuits. emitter-base terminal input signal is applied and in collector-base terminal output is taken from it. 5.What are the characteristics of CB? since it has a low input resistance and a high output resistance, current gain of less than 1. The input and output signals in the common-base circuit are in phase 6.What is transistor and why it is called like that? Because it transfers the input signal from low resistance to high resistance 7.Define α, β, γ, what is the relation between them? These are current gains in CB,CE,CC configurations respectively, ; αγ= 8.Compare CE,CC,CB configurations?

9.Define cut-off, active and saturation regions? Cut off- both emitter Je, collector Jc junctions in Reverse bias Active – Je forward, Jc Reverse bias Saturation – Je,Jc in forward bias 10.What do you understand by input and output characteristics? characteristics gives the information about input resistance and output resistances. 11.Explain the physical structure of a BJT? One N type material is sandwiched between two P type materials or One P type material is sandwiched between two N type materials , widths (C>E>B), doping concentration(E>C>B) 12.Explain Early Effect? The variation in base width of BJT due to variation in the applied basecollector voltage 13.Why does the emitter current increase with increase in reverse bias at the collector junction? Due to breakdown in collector junction 14.What is meant by collector reverse saturation current? Minority carriers flow throw collector junction when it is connected in reverse bias 15.Write the collector current expression for BJT in CB configuration? Cutoff region Ic=0 Active regionIc= βIb Saturation Ic<βIb 16.Give the values of VCE Sat for the transistor BC107. Vce sat=0.2v 17.Explain the performance of the transistor as an electronic switch? When transistor is in cut off it works as off switch, when transistor is in saturation it works as on switch 18.Is the BJT Transistor a current controlled device or a voltage-controlled device? Current controlled current device

19.Draw the symbolic representations of NPN and PNP transistors.

20.Sketch the characteristics of a BJT in Common-Emitter Configuration.

21.Why is it called Common-Emitter configuration? Emitter terminal is common to input and out put 22.What is a “load-line”? What is its significance? Differentiate between a.c. load line and d.c. load line. Load line specifies the operating point, Dc load line is the line based on the relation between output voltage and currents when input is zero, Ac load line is the line which pocess through the Q point with slope of (-1/Rac, Rac= Rc//Rl) 23.What is meant by Q- point? It specifies the correct biasing at which gives required amplification 24.What is Biasing and why it is needed for transistor? The process of giving proper supply voltage and resistances for obtaining desired operating point 25.What are the methods of transistor biasing, which type is best and why? Fixed bias, Emitter feedback bias, Collector to base bias, Collector- emitter feedback bias, self bias(voltage divider bias), in these all self bias is best because it is more stable for a greater range of input signal

26.What is thermal Runaway? It is a situation where an increase in temperature changes the conditions in a way that causes a further increase in temperature. 27.Thermistor temperature co efficient is? It may be + or – based on the material used. 28.Define two port networks, types, which one is best for bjt and why? Z, Y, h, g, ABCD parameters, best one is hybrid parameters bczthethese gives all parameters about amplifier like input, output impedance, voltage and current gains. 29.What are the typical h-parameter values for a transistor?

30.Draw the H parameter equivalent circuit?

31.Compare CB,CE,CC amplifiers, and what are the applications?

1.What are the comparisons and differences between a BJT and a JFET? BJT current controlled current device, Fet voltage controlled current device, in BJT current produced by holes and electrons, but in FET current produced due to any one only, 2.What is meant by a unipolar device? Why is a JFET known as a Unipolar Device? In which device current produced due to one polarity (electron or hole), in jFET current produced due to one only(N channel JFET- electrons, pchannel JFET- holes). 3.Draw the symbols of JFET, MOSFET?

4.What are the typical applications of a JFET? Buffer, RF amplifier, cascade amplifier, variable resistor in op amps, mixer circuit, memory cell

5.What are the characteristic parameters of a FET? What are the relations between them?

Trans conductance gm=dId/dVgs Drain resistance Rd=dVds/dId Amplification factor µ=-dVds/dVgs µ=RdXgm 6.What are n-channel and p-channel JFETs? How are they different from each other? In N channel jfet , the channel made by Ntype material so current exist from Drain to source due to Electrons (ajority carriers) only. In P channel jfet , the channel made by P type material so current exist from Drain to source due to holes (ajority carriers) only 7.Give the names/numbers of a few commercially available JFET devices. 2N3954A- low noise low drift monolithic dual, N channel jfet BF245A, J111,J112: N channel jfet 8.What are the various possible configurations in which a JFET can be connected? What are the typical applications of each? Common Drain: Buffer Common Sourse: Amplifier Common Gate: Amplifier (high frequency) 9.Explain pinch off voltage and region? Pinch off voltage is the drain to source voltage after which drain current becomes almost constant 10.Explain the regions in Transfer characteristics, output characteristics of JFET?

11.What is the drain current and Trans conductance equation in JFET? Id= Idss(1-(Vgs/Vp))2; gm=gmo(1-( Vgs/Vp)) 12.What is a MOSFET? What are the possible types in a MOSFET? Metal oxide semiconductor FET Types are N channel, P channel – Enhancement and Depletion Type Mosfets. 13.Which transistor parameters vary with temperature? Reverse saturation current, current gains, trans conductance 14.What is meant by ‘load line’? Load line indicates the output side voltage, current relation based on input voltage or current. Inter section point of AC,DC load lines indicates Operating point(Q point) 15.What is meant by the “operating point” of a transistor? Operating point specifies output voltage and currents at required operating region. 16.Why is a capacitor used to shunt the emitter resistor of self-biased transistor? To get more stability we need to establish current series feedback (-ve) for DC input but for Ac input that is not required so.. 17.Why is the self-bias circuit preferred over other possible biasing circuits? More stable with respect to Tempareture, β, 18.Define Stability factor and explain its significance. Stability factor represents changes with in the output current due to changes in Temperature, transistor (β), leackage current, base emitter voltage 19.What is the advantage of a FET biasing circuit above BJT biasing? FET is a voltage controlled current device so no need of extra circuitry 10.What is the need for the capacitor CS? To get more stability we need to establish current series feedback (-ve) for DC input but for Ac input that is not required so.. 11.Why are the coupling capacitors required? To filter the Dc term from the Input signal , Collector output in amplifiers. 12.What is meant by thermal stabilization? Maintain a constant operating point when temperature varies 13.Explain why reversal of phase occurs in a BJT CE Amplifier.\ As Base voltage increases, base current increases, then collector current increases so voltage drop across Rc increases so out put voltage decreses. 14.What happens if an amplifier is biased at cutoff or at saturation? In cutoff region Ic is 0, in saturation region Vce is almost Zero.

15.What is the significance of the bandwidth of an amplifier? Bandwidth specifies the input signal frequency range that can be applied to amplifier to get maximum gain. 16.What is meant by Gain-Bandwidth Product? What is its significance?

The name itself expressing it is the product of gain of a device and its bandwidth. For any system (circuit) gain bandwidth product is constant, if gain increases bandwidth decreases vice versa. 17.What are the advantages of using a FET instead of a BJT? FET has high input impedance, lower noise, low to medium gain, 19.Can we interchange the source and drain terminals in a FET circuit? Can we do the same with the emitter and collector terminals of a BJT circuit? We can interchange drain and source but we cannot change emitter and collector because emitter and collectors dimensions and doping concentration is different 20.What is a MOSFET? How is it different from a JFET? What are its typical applications? Metal oxide semiconductor can be operated in both depletion and enhancement modes, but Junction field effect Transistor can be operated in depletion mode only. 21.Explain why reversal of phase does not occur in a BJT CC Amplifier? As Base voltage increases, base current increases, then collector current increases so voltage drop across Re increases so output voltage increases 22. Why is the Common Collector Amplifier called as Emitter Follower? In common collector amplifier out will be taken across emitter so its called as emitter follower

Special purpose Devices: 1.Explain the working of SCR.

2.Define holding current. Holding current is the specified minimum current that must be flowing from anode to cathode (with no gate current) and still be guaranteed that the SCR will not turn off. 3.What are the specifications of the SCR ? gate trigger voltage, gate trigger current, holding current, on-state voltage, peak gate power dissipation.

4.What is UJT, explain the input characteristics of it?

unijunction transistors are constructed from separate P-type and Ntype semiconductor materials forming a single (hence its name Uni-Junction) PNjunction within the main conducting N-type channel of the device.

5.What is the symbol and principle of operation of Tunnel Diode?

According to the classical laws of physics a charged particle sin order to cross an energy barrier should possess energy at least equal to the energy barrier. Hence the particle will cross the energy barrier if its energy is greater than the barrier and cannot cross the barrier if its energy is less than the energy barrier. But quantum mechanically there exists non zero probability that the particle with energy less than the energy barrier will cross the barrier as if it tunnels across the barrier. This is called as Tunneling effect. 6.Explain the V-I characteristics of Tunnel diode?

7.What is the symbol and principle of operation of Varactor Diode? According to the classical laws of physics a charged particle sin order to cross an energy barrier should possess energy at least equal to the energy barrier. Hence the particle will cross the energy barrier if its energy is greater than the barrier and cannot cross the barrier if its energy is less than the energy barrier. But quantum mechanically there exists non zero probability that the particle with energy less than the energy barrier will cross the barrier as if it tunnels across the barrier. This is called as Tunneling effect. 8.What is the symbol and principle of operation of SchottkyBarrier Diode? 9.What is the symbol and principle of operation of photo Diode?

dsp 1. Define discrete time and digital signal. Discrete time signal is continuous in amplitude and discrete in time, where Digital signal is discrete in time and amplitude. 2. Explain briefly, the various methods of representing discrete time signal Graphical, Tabular, Sequence, Functional representation 3 Define sampling and aliasing. Converting a continuous time signal into discrete time signal is called as Sampling, Aliasing is an effect that causes different signals to become indistinguishable. 4. What is Nyquist rate? Its the sampling frequency which is equal to twice of Continuous time signal which has to be sampled. 5. State sampling theorem. It states that , To reconstruct the continuous time signal from its Discrete time signal, The sampling frequency should be more than twice of continuous time signal frequency.

6. Express the discrete time signal x(n) as a summation of impulses.

7. How will you classify the discrete time signals? Causal and Non causal, Periodic and non periodic, even and odd, energy and power signals 8.. When a discrete time signal is called periodic? If some set of samples repeats after a regular interval of time then its called as periodic. 9. What is discrete time system? If a system's excitation and responses are both discrete time signals then its called as discrete time system. 10. What is impulse response? Explain its significance. The response of a system when the excitation is Impulse signal is called as impulse response. it also called as Natural response, free forced response. 11. Write the expression for discrete convolution.

12. classifying discrete time systems. Causal, Non causal, time variant, time invariant, Linear, non linear, stable and unstable system. 13. Define time invariant system. If a system's operation is independent of time then its time invariant, i.e delayed system response is equal to system's response for delayed input. 14. What is linear and nonlinear systems? If a system satisfies homogeneity principle and superposition principle then it is Linear. if not Non linear. 15. What is the importance of causality? causality states that system's response should depend on present and past inputs only not on the future inputs. so causal systems are realizable. 16. What is BIBO stability? What is the condition to be satisfied for stability?

If a system's response is Bounded for Bounded excitation then its BIBO stable. For stable system the impulse response should be absolutely sum able . 17. What are FIR and IIR systems? FIR: system's impulse response contains finite no. of samples IIR: system's impulse response contains infinite no. of samples 18. What are recursive and non recursive systems? give examples? A Recursive system is one in which the output depend on it,s one or more past outputs while a non recursive is one in which output is independent of output. Ex: any system with feedback is Recursive , without feedback is non recursive. 19. Write the properties of linear convolution. 1) x(n)*y(n)= y(n)*x(n) 2) [x(n)+y(n)]*z(n)=x(n)*z(n)+y(n)*z(n) 3) [x(n)*y(n)]*z(n) =x(n)*[y(n)*z(n)] 20. Define circular convolution. Circular convolution is same as linear convolution but circular is for periodic signals. 21. What is the importance of linear and circular convolution in signals and systems? Convolution is used to calculate a LTI system's response for given excitation. 22. How will you perform linear convolution via circular convolution? circular convolution with the length of linear convolution length (l+m-1) results linear convolution. 23. What is sectioned convolution? Why is it performed? If any one of the given two sequences length is very high then we have to go for sectioned convolution. 24. What are the two methods of sectioned convolution? 1) Over lap-Add method. 2) Over lap save method. 25. Define cross correlation and auto-correlation? Auto correlation is a measure of similarity between signals and its delayed version as a function of time delay. cross correlation is a measure of similarity between two signals as a function of time delay between them. 26. What are the properties of correlation?

1) R12(T)≠R21(T) 2) R12(T)=R21*(-T) 3) if R12(T)=0, both signals are orthogonal to each other 4) Fourier transform of auto correlation gives energy spectral density.

1.

Define

2.

What

one-sided

is

region

and

two-sided

of

convergence

Z-transform.

(ROC)?

The region of Z magnitude (|Z|) for which x(n).|Z|-n is absolutely summable 3. State the Initial value and final value theorem with regard to Z-transform.

4.

Define Z-transform of unit step signal. Z/(Z-1) ROC |z|>1 5. What are the different methods available for inverse Zs-transform? Residue method, Partial fractions method, Long division method, Convolution integral method 6. When the z-domain transfer function of the system can be directly obtained from s-domain transfer function? When input is an Impulse sampled signal. 7. Define the transfer function of an LTI system. For Discrete time systems: Z transform of impulse response of system For Continuous time systems: Laplace transform of impulse response 8. Write the transfer function of Nth order LTI system.

9. Give the importance of convolution and deconvolution operations using Ztransform. 10. Give the conditions for stability of an LTI discrete time system in z-plane.

The ROC should contain unit circle with in it. 11. Explain when an LTI dicrete time system will be causal. The ROC should contain infinite. i.e system impulse response is a right sided signal. 12. State the convolution property of Z-transform. ------------->

------------->

13. 14.

state

the

Z-transform click here

properties of

of

Z click various

transform? here signals?

Part-III: DFT & FFT 1. Define DFT of a discrete time sequence?

2.

Define

inverse

DFT.

3. What is the relation between DTFT and DFT?

4. What is the drawback in Fourier transform and how is it overcome? Fourier transform is that it is not truly realizable in practice but we can get closer, it is not applicable to all signals, so we go for Laplace in continuous , Z in discrete. 5. List any four properties of DFT . linearity Property : ax1(n)+bx2(n)→aX1(ω)+bX2(ω)

Duality Complex Circular

Property: conjugate shift

X(N)⟷Nx[((−k))N]

property:

x∗(n)⟷X∗((K))N=X∗(N−K)

property: x(n)exp(j2ΠKn/N)⟷X((K−L)

6. What is FFT, What it's importance? FFT stands for Fast Fourier Transform, this is same as DFT but algorithm is different by FFT with in lees time we can compute Fourier transform compared to DFT. 7. compare FFT and DFT? DFT and FFT both are used to represent a discrete time signal in frequency domain, But DFT procedure is formula based where FFT is algorithm based, FFT is more efficient and faster than DFT, i.e if a sequence contains N samples then to calculate DFT no. of multiplications and additions required are: N2 , N(N-1) FFT no. of multiplications and additions required are : (N/2) log2(N), N log2(N) 8. What are the various algorithms to calculate FFT? Decimation In Time (DIT), Decimation In frequency (DIF) 9. Draw the DIT FFT structure with the length of 8?

10. Draw the DIF FFT structure with the length of 8?

11. What is phase factor or twiddle factor? -j2π/N It is defined as WN = e 12. What are the phase factors involved in all stages of computation in the 8-point DIT radix-2 FFT? First stage: W80 Second stage: W80, W82 Third stage: W80, W81, W82, W83 13. Draw the basic butterfly diagram or flow graph of DIT radix-2 FFT?

14. Draw the basic butterfly diagram or flow graph of DIF radix-2 FFT?

15. What are the phase factors involved in all stages of computation in 8-point DIF radix-2 FFT? First stage: W80, W81, W82, W83 Second stage: W80, W82 Third stage: W80 16. What is magnitude and phase spectrum? Magnitude spectrum is the graph between Fourier transform magnitudes and frequency. Phase spectrum is the graph between Fourier transform phases and frequency.

Microprocessor Microprocessor Viva Question with Answer Q1) What is a Microprocessor ? Ans: Microprocessor is a program controlled single chip devices, which fetches the instruction from memory, then decodes it and executes. Q2) What is a Instruction set ? Ans: Instruction set is the set of Instructions that a microprocessor can execute. Q3) What is Bandwidth ? Ans: Number of bits processed by processor in one instruction is its Bandwidth. Q4) On what does Microprocessor speed depends on ? Ans: It depends on the Data Bus Width Q5) What are mnemonics ? Ans: Mnemonics are instructions or commands to perform a particular operation. Like MOV or ADD or SUB or MIV etc Q6) What are flags in Microprocessor ?

Ans: There are different flags in microprocessor like carry flag, Interrupt flag, zero flag, parity flag, overflow flag, trace flag, direction flag etc Q7) Name 1st/2nd/3rd/4th generation microprocessor ? Ans: 1st generation ---- PMOS ---- 4 bits 2nd generation ---- NMOS ---- 8 bits 3rd generaton ---- HMOS ---- 16 bits 4th generation ---- HCMOS ----32 bits Q8) What is the maximum clock frequency of 8086 microprocessor ? Ans: Its 5MHz Q9) What is Maskable and non- maskable interrupts ? Ans: Interrupt that can be turned off by programmer is Maskable interrupts and those which can not be turned off by programmers are non maskable interrupts. Q10) What is the disadvantages of Microprocessor ? Ans: It has limitations on size data and most microprocessor does not support floating point operations.

Antennas and Wave Propagation Viva Questions: Q1) What is an Antenna ? Ans: we have several definitions for antenna, they are as follows : An Antenna is a transducer,i.e, it converts electrical signals to Electromagnetics Wave at the transmitter and vice versa at the receiver.  An Antenna is a sensor and radiator of EM waves.  An Antenna is a perfect impedance matching device.  Any piece of conducting material or wire acts as an Antenna on excitation. Q2) What is a Isotropic radiator ? 

Ans: It is an Antenna which radiates equally in all directions. It is also called as reference antenna. Q3) What is a Omni Directional Antenna ? Ans: It radiates equally in all directions in azimuthal plane and radiates in single direction in elevation plane. Q4) Name some of the Antenna Parameters ?

Ans: some of the Antenna parameters are as follows:  Antenna Impedance  Radiation pattern  Radiation Intensity  Directive Gain  Power Gain  Efficiency  Effective area  Front to Back ratio  Antenna Bandwidth Q5) What is a Radiation Pattern ? Ans: Radiation pattern is the variation of electric field strength with respect to elevation angle. Q6) What is Radiation Intensity ? Ans: It is the radiated power per unit solid angle. Q7) What are the units of Solid angle ? Ans: Steradian Q8) What is the effective length of an Antenna ? Ans: It is the length of Antenna which is responsible for transmission or reception of EM waves. It is always less than the actual length of an Antenna. Q9) What is Antenna Bandwidth ? Ans: It is the range of frequency over which antenna will perform satisfactory without any change. Q10) What is Antenna Arrays ? Ans: It is the system of Antennas similarly oriented or dis similarly oriented to achieve maximum gain or directivity. Q11) What are advantages of Antenna Arrays ? Ans: Advantages:  Enhancement in gain  Enhancement in directivity  Reduction in Beam width

Q12) What are disadvantages of Antenna Arrays ? Ans: Disadvantages:  Side lobes increases  Cost increases  complexity increases  more space is required for installation Q13) What is a Broad side Array ? Ans: If the principal maxima or Radiation pattern is perpendicular to axis of array then it is Broad side array. Q14) What is End fire Array ? Ans: If the principal maxima or Radiation pattern is along the axis of array then it is Broad side array. Q15) What is Front to Back ratio in Antennas ? Ans: It is the ratio of radiation in desired direction to that of radiation in opposite direction. For an ideal Antenna it is infinity.

Microwave Engineering Viva Questions: Q1) What is Transit Time ? Ans: It is the time taken by the electrons to travel from cathode to anode. Q2) Why can't Conventional tubes be used at microwave frequencies ? Ans: Conventional tubes can't be used at microwave frequencies because of transit time effect. Lead inductance and inter electrode capacitance of the device will finally limit the output which may even be zero. Q3) What is the operating principle of Reflex Klystron ? Ans: It works on the principle of velocity modulation and current modulation. Q4) What is Velocity Modulation ? Ans: Variations in velocities of electrons in the electron beam is called velocity modulation. Q5) What is Current Modulation ? Ans: Variation in the current density of electron beam is called current modulation.

Q6) How does bunching occur in reflex klystron ? Ans: A reflex electron while passing the gap when the gap voltage is zero passes with no change in velocity. An electron leaving the gap earlier during slightly positive voltage would travel further into repeller space and hence would take longer time than the reference electron to return to gap. An electron leaving the gap late will face slightly negative voltage and gets retarded. So it returns back after a shorter travel in repeller space. Thus all the electrons will arrive in bunch. This is Bunching effect and this is how bunching takes place in reflex klystron. Q7) What modes are generally used in Reflex Klystron ? Ans: 1suffix(3/4) and 2suffix(3/4) are the mostly used modes in reflex klystron. Its modes are generally Nsuffix(3/4) where N is any Integer. Q8) What is the operating frequency and power output of reflex klystron ? Ans: Frequency Range: 4GHz to 200GHz Output Power: maximum 3W in X Band to 10mW at 200GHz Q9) What is the maximum theoretical efficiency by reflex klystron ? Ans: 22.7% for 1suffix(3/4) mode Q10) What is Mechanical Tuning and Electronic Tuning in reflex klystron ? Ans: Variation in frequency of resonance of cavity by varying its dimensions by mechanical methods like adjusting screws is called Mechanical tuning. And Variation of frequency by adjusting repeller voltage is called Electronic tuning. Email ThisBlogThis!

Computer Networks Viva Questions: Q1) Define Network? Ans: A Network is a set of devices connected by physical media links. A network is recursively a connection of two or more nodes by a physical link or two or more networks connected by one or more nodes. Q2) What is a link? Ans: At the lowest level, a network can consist of two or more computers directly connected by some physical medium such as coaxial cable or optical fiber. Such a physical medium is called as link. Q3) What is a Gateway or Router?

Ans: A node that is connected to two or more networks is commonly called as Router or Gateway. It generally forwards message from one Network to another. Q4) What is Point to Point Link? Ans: If the physical links are limited to a pair of nodes it is said to be point to point link. Q5) What is Multiple Access? Ans: If the Physical links are shared by more than two nodes, it is said to be multiple access. Q6) What is a Node? Ans: A network can consist of two or more computers directly connected by some physical medium such as coaxial cables or optical fiber. Such a physical medium is called as links and the computer it is connected is called as Nodes. Q7) What are the key elements of protocols ? Ans: Key elements of protocol are: a) Syntax: It refers to the structure or format of the data, that is the order in which they are presented. b) Semantics: It refers to the meaning of each section of bits. c) Timing: It refers to when data is to be sent and how fast it should be sent. Q8) What are the design issues of a Computer Network ? Ans: a) Connectivity b) cost- effective resource sharing c) support for common services d) performance Q9) Define Routing ? Ans: The process of determining systematically how to forward messages toward the destination nodes based on its address is called Routing. Q10) What is Multiplexing ? Ans: Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

What is meant by D-FF? D-flip flop stands for Delay flip-flop, it delays input by one clock pulse

What is the basic difference between Latches and Flip flops? Latches are monostable and flip-flops are bistable What is a multiplexer? It is used to multiplex data from different sources normally used in TDM How can you convert an JK Flip-flop to a D Flip-flop? Connect J to D and K to not(D) What is Race-around problem? How can you rectify it? Race around condition occurs in a JK flip-flop when both the inputs are set to '1', it can be rectified using edgetriggered flip-flop or using master-slave flip-flops What do you mean by zener breakdown and avalanche breakdown? zener breakdown takes place when very high voltage is applied to the diode this results in very high reverse current, as voltage is further increased minority carriers gain further momentum and strike atoms releases more carriers, which results in further increase in temp. It becomes vicious cycle and leads to avalanche breakdown or on other words "thermal runaway". What is sampling theorem? sampling frequency should be atleast twice the maximum freq present in the signal What is impulse response? response given by a digital system when impulse signal is applied to it. Used to find out stability of system What do you mean by half-duplex and full-duplex communication? Explain briefly. half-duplex: either sender or receiver can use the channel at one time eg walky-talky and full-duplex: sender or receiver or both can use the channel at one time eg telephone) For asynchronous transmission, is it necessary to supply some synchronizing pulses additionally or to supply or to supply start and stop bit?

20.Differentiate between DTFT and DFT. Why it is advantageous t o u s e D F T i n c o m p u t e r s rather than DTFT?In DTFT, frequency appears to be continuous. But, in DFT, frequency is discrete.This property is useful for computation in computers. 21.How to perform linear convolution using circular convolution? If two signals x (n) and y (n) are of length n1 and n2, then the linear convolutedoutput z (n) is of length n1+n2-1. Each of the input signals is padded with zeros tomake it of length n1+n2-1. Then circular convolution is done on zero paddedsequences to get the linear convolution of original input sequences x (n) and y (n). 22.What is meant by correlation? Correlation is the measure of similarity between two signal/waveforms. Itcompares the waveforms at different time instants. 23.What is auto-correlation? It is a measure of similarity of similarity of a signal/waveform with itself. 33.What is a Digital Signal Processor (DSP)? Microprocessor specifically designed to perform fast DSP operations (e.g., FastFourier Transforms, inner products, Multiply & Accumulate) • Good at arithmetic operations (multiplication/division) • Mostly programmed with Assembly and C through IntegratedDevelopment Environment (IDE) 34.Differentiate between RISC and CISC architectures. RISC EmphasisonsoftwareSingle-clock,reducedinstructiononlylargecodesizeBetter Ccompilers CISC EmphasisonhardwareIncludesmulti-clock complexinstructionsSmallcodesizesPoor Ccompilers 35.Differentiate between General purpose MPU(Micro Processor Unit) and DSP Processor MPU are built for a range of general-purpose functions such as :Data manipulationMath calculationsControl systemsThey run large blocks of softwareThey are used in real-time and in unreal-time systems DSPs are single-minded, dedicated to: Perform mathematical calculationsSmall blocks of softwareHave a predictable execution timeReal-time onlyCould assist a general-purpose host MPU 3 6 . W h a t DSP

i s

p i p e l i n i n g ?

ArithmeticVarying internal formatMultiple memory accessSpecial addressing modeVery large internal memory Microprocessor General purposeFixed internal formatSingle memory accessGeneral addressing modeVery large external memory

40.Differentiate between floating point DSP and fixed point DSP. .Fixed Point/Floating Point • fixed point processor are :i . c h e a p e r i i . s m a l l e r i i i . l e s s p o w e r c o n s u m i n g i v . H a r d e r t o p r o g r a m 1.Watch for errors: truncation, overflow, roundingv . L i m i t e d d y n a m i c r a n g e vi.Used in 95% of consumer products • floating point processorsi . h a v e l a r g e r a c c u r a c y i i . a r e m u c h e a s i e r t o p r o g r a m i i i . c a n a c c e s s l a r g e r m e m o r y iv.It is harder to create an efficient program in C on a fixed point processors than on floating point processors 43.Explain Von-Neumann and Harvard architectures PipelinePipelineStageStage PFPFDDEE Execute instructionExecute instructionRoute opcode to functional unitRoute opcode to functional unitDecode instructionDecode instructionGenerate program fetch addressGenerate program fetch addressRead opcodeRead opcode DescriptionDescription Floating Point Fixed Point A pplicationsModemsDigital Subscriber Line (DSL)Wireless Base stationsDigital Imaging3D GraphicsSpeech RecognitionVoice over IPApplicationsPortable Products2G, 2.5G and 3G Cell PhonesDigital Audio PlayersDigital Still CamerasVoice RecognitionHeadsetsFingerprint Recognition

What are the advantages of integrated circuits?     

increased package density. Cost reduction . Increased system reliability. Improved functional performance. Increased operating speeds.

   

Reduction in power consumption. 2.What are the popular IC packages available? Metal can package. Dualinlinepackage. Ceramic flat package. 3.What is an operational amplifier. An operational amplifier is a directcoupled high gain amplifier consisting of one or more differential amplifiers, it can be used to perform a variety of mathematical operations. 4.What is the Internal Structure of op-amp and explain each block in brief?

5.What are the characteristics of an ideal op-amp.       

Open loop voltage gain is infinity. Input impedance is infinity. Output impedance is zero. Bandwidth is infinity. Zero offset. CMRR Infinite. Slew rate Infinite.

6.What are the DC,AC Characteristics of OP-Amp? DC Characteristics: Input Bias Current, Input off set Current, Input offset voltage, Thermal Drift. AC Characteristics: Slew Rate, Frequency compensation 7.What is input offset voltage? It is the voltage Imbalance b/w two input terminals of op-amp. 8.Define input offset current. The difference between the bias currents at the input terminals of the 9.Define CMRR of an opamp? It is the ratio b/w Differential mode gain and common mode gain CMRR= Ad/Ac 10.what is the effect of high frequency on its performance? The openloopgain of op-ampdecreases at higher frequencies due to the presence of parasitic capacitance. The closedloopgain increases at higher frequencies and leads to instability. 11.What is the need for frequency compensation in practical op-amps? When large bandwidth and lower closed loop gain is desired, to improve the stability. 12.What are the frequency compensation methods?

 

Dominantpolecompensation Pole-zerocompensation 13.Define slew rate. The maximum rate of change of output voltage causedby a step input voltage. An ideal slew rate is infinite. Units- v/µs 14.Can we use IC 741 for high frequency applications? No, IC741 has a low slew rate. 15.Why slew rate is not infinite in Ideal op-amp? There is a capacitor withinor outside of an op-ampto prevent oscillation. 16.What are the applications of op-amps? Linear: Adder, subtracter, voltage to current converter, current to voltage converters, instrumentation amplifier, analog computation, power amplifier, Integrator, differentiator etc. Non linear: Rectifier, peak detector, clipper, clamper, sample and hold circuit, log amplifier, anti-logamplifier, multiplier 17.What is an instrumentation amplifier and the need for? In a number of industrial and consumer applications, the measurement of physical quantities is usually done with the help oftransducers. The output of transducer has to be amplified So that it can drive the indicator or display system. This function isperformed by an instrumentation amplifier. 18.What are the features of instrumentation amplifier?

    

high gain accuracy high CMRR high gain stability low dc offset low output impedance 19.What are the applications of V-I and I-V converters? V-I:Low voltage dc and ac voltmeter, L E D Tester, Zener diode tester I-V: Digital to Analog converter, Light intensity indicator, photo diode detector 20.What do you mean by a precision diode? The major limitation of ordinary diode is that it cannot rectify voltages below the cut in voltage of the diode the precision diode is capable of rectifying input signals of the orderof millivolt. 21.What are the applications of precision diode.



Half waveRectifier

  

Full Wave rectifier Peak value detector Clipper, Clamper

22.What are the applications of Log amplifier? Multiplier, divider. 23.What are the limitations of the basic differentiator circuit? At high frequency, a differentiator may become unstable and break into oscillations, The input impedance decreases with increase in frequency. 24.What are the limitations of the basic Integrator circuit? At low frequency, a integrator may become unstable and break into oscillations, The input impedance decreases with decrees in frequency. 25. What is a comparator? Which compares a signal with a known reference voltage . its output is either + Vsat or -Vsat . 26.What are the applications of comparator? Zero crossing detector 27.Why can’t we use comparator to convert sin wave into square wave? If noise exist in sinusoidal signal at zero volts unwantedly out put varies b/w + Vsat and -Vsat . 28.What is a Schmitt trigger? It is a regenerative comparator. It converts sinusoidal input into a square wave output. 29.What is a multivibrator? It is a regenerative circuit that is used extensively in timing applications. It has two states either stable or quasi-stable depending on the type of multivibrator. 30.What is monostable multivibrator? Generates a single pulse of specified duration in response to each external trigger signal. It has only one stable state. Its is also called as One-shot generator. 31.What is an astable multivibrator? It is a free running oscillator having two quasi-stable states. So it is a Square wave generator. 32.What is a bistable multivibrator? Bistable multivibrator is one that maintains a given output voltage level unless an external trigger is applied .Application of an external trigger signal causes a change of state, and this output level is maintained indefinitely until an second trigger applied . Thus, it requires two external triggers before it returns to its initial state

1. What are the disadvantages of Analog communication? Its not reliable, Noise effect is more on the signals, Power required for signal transmission also more, Circuit complexity is more and costly.

2. What are the Advantages of Digital Communication? Reliable, Noise effect is very less, power consumption is very less, various Digital ICs are available so circuits not complex , cheap, Error detection and correction is also possible. 3. What are different types of digital modulation? ASK, FSK, PSK, PCM, DPCM,Delta modulation, Adaptive Delta modulation etc.. 4. How to convert an analog signal into digital signal? Blocks: Anti aliasing filter, Sampler, Quantizer, encoder. 5. Define the functionality of Sampler, Quantizer? Sampler: converts a continuous time signal into discrete time signal. Quantizer: converts continuous in amplitude signal into discrete in amplitude signal. 6. What are some Coding techniques? Pulse code modulation, Differential pulse code modulation, Delta modulation, Adaptive delta modulation. 7. What is Sampling? Converting a continuous time signal into discrete in time signal is called as Sampling (similar to cutting a bread into slices) 8. Define Sampling theorem? To reconstruct the Continuous time signal from discrete time signal ,the sampling frequency should be more than equal to twice of Continuous time signal frequency(max). 9. What is Nyquist Rate? If the sampling frequency is twice of Continuous time signal frequency(max), then that is called as Nyquist rate. 10. How many types of samplings are their? Explain briefly? Impulse Sampling, Natural sampling, Flat top sampling.

11. What is aliasing effect? How to overcome it? Due to imperfect sampling the signals will be interfered in frequency domain i.e called aliasing effect in sampling. if sampling theorem satisfied in sampling or first by passing signal from anti aliasing filter before sampling then aliasing effect will be reduced 12. What are the Analog pulse modulation methods? Pulse amplitude modulation, pulse width modulation and pulse position modulation.. 13. Define Pulse amplitude modulation? The carrier pulse height (amplitude) proportional to amplitude of messege signal. 14. Define Pulse width modulation? The carrier pulse width proportional to amplitude of message signal. 15. Define Pulse position modulation? The carrier pulse position proportional to amplitude of message signal. 16. Compare PAM, PWM, PPM?

17. What is Amplitude shift Keying (ASK) ? It represent the digital data as variations in amplitudes in carrier wave. i.e '1' represented by transmitting a fixed amplitude carrier wave for the bit duration with constant frequency. 18. What is Phase shift keying ( PSK)? It represent the digital data as variations in phase shift in carrier wave. i.e '1' represented by 0 phase shift carrier wave , where '0' represented as 180 phase shift incarrier wave for the bit duration with constant frequency 19. What is Frequency shift keying (FSK) ? It represent the digital data as variation in frequency in carrier wave, i.e for '1' more than carrier frequency , for '0' less than carrier frequency. 20. What is Binary Phase shift Keying (BPSK) ? for each one bit of binary data (0 & 1) carrier phase will be changed (two different shifts: 0, 180) 21. What is Quadrature Phase shift Keying (QPSK) ? for each two bits of binary data (00,01,10 & 11) carrier phase will be changed (four different shifts : 45, 135, -45, -135) 22. What is the difference between Bit Rate and Baud Rate? Bit rate represents Bits per sec,Baud rate represents no. of symbols per second i.e. in communications the no. of bits transmitted per sec is called as Bit Rate (units bps) and The no. of times a signal (here carrier) changes its state (change in freq, phase, amplitude) per sec is called as Baud rate. 23. What is bandwidth of BPSK signal? 2Fc, if Fc represents carrier frequency 24. Compare ASK, PSK and FSK.? Bandwidth: ASK< PSK < FSK Power: ASK PSK > FSK Signal to Noise Ratio: ASK < PSK < FSK 25. Why is ASK called as ON-OFF keying? When input data is 1 then output is carrier, if input is 0 out put is zero. so its looks like a switch which will switch on when input is 1 and off when input is zero

1. What is difference between Amplifier and Attenuator? Both are linear systems but Amplifier's gain is more than unity (+ve dB), Attenuator gain is less than unity (-ve dB)

2.Which Amplifier will amplify voltage and current? common emitter amplifier 3. What are the advantages over single stage amplifier? In single stage amplifier if we try to get more gain, bandwidth will be decreased viceversa. So get more bandwidth and gain combination we generally use multistage amplifier. but multistage amp bandwidth is less than single stage. 4.what are the classifications of Multistage amplifiers? Based on Active device used: BJT and FET Based on type of coupling: RC coupled, Transformer coupled and Direct coupled amplifiers. 5. What are the different BJT multistage amplifier configurations? CE+CE, CE+CC, CE+CB, CC+CC Amplifiers 6. What are the different FET multistage amplifier configurations? CS+CS, CS+CD, CS+CG and CD+CD Amplifiers 7. what is the ratio of transformer coil turns in transformer coupled amp? 1:1 8. Define cut off frequency? It is the frequency at which the gain is 70.07% of it's maximum or 3dB lesser than maximum 9. what are the formulas for low and high cut off frequencies of multistage amplifiers?

where Fl, Fh represents

low and high cut off freq for multistage amp fl,fh represents low and high cut off freq for single stage amp 10. what is the gain of multistage amp? It is equal to square of single stage amp gain. Feedback amplifiers: 1. What is meant by feedback, what are the different types? Feedback is a path which establish a connection from output of a device to it's input. It is two types: +ve feedback, -ve feedback.

2. What is -ve feedback and where it is used? If a fraction of output is subtracted from the input then that is called as -ve feedback. it is used get a stable operation. if we implement -ve feedback then that becomes an amplifier. 3.What is +ve feedback and where it is used? If a fraction of output is added to the input then that is called as +ve feedback. it is used get a output with out input like oscillators. 4. what are the different -ve feedback techniques in amplifiers? Voltage- Series amplifier, Voltage - Shunt Amplifier, Current - Series Amplifier, Current - shunt amplifier. 5. what happens to the gain if we establish -ve feedback to the amplifier? Decreased 6. what happens to the Bandwidth if we establish -ve feedback to the amplifier? Increased. 7. compare all -ve feedback amplifiers in terms of input and output amplifiers? Input imp Output imp Voltage- Series Amplifier decreased increased Voltage - Shunt Amplifier decreased decreased Current - Series Amplifier increased increased Current - Shunt Amplifier increased decreased 8. what are the other names of different -ve feedback amplifiers? Voltage- Series Amplifier : Series- shunt amplifier Voltage - Shunt Amplifier : Shunt - Shunt amplifier Current - Series Amplifier : Series - Series amplifier Current - Shunt Amplifier : Shunt - Series amplifier 9. what are the different types of distortions present in amplifier? Harmonic, frequency, phase distortions 10. self bias circuit contains which feedback? Voltage - Series feedback 11. collector to emitter feedback circuit contains which feedback? Voltage - Shunt feedback. 12. what is the forward path gain and feedback gain of voltage - series feed back amplifier?

forward path gain= g21, feedback path gain= h12 13. what is the forward path gain and feedback gain of voltage - shunt feed back amplifier? forward path gain= Z21, feedback path gain= Y12 14. what is the forward path gain and feedback gain of current - series feed back amplifier? forward path gain= Y21, feedback path gain= Z12 15. what is the forward path gain and feedback gain of current - shunt feed back amplifier? forward path gain= h21 , feedback path gain= g12

1. What is an Oscillator? It is a circuit which acts as a generator, generating the output signal which oscillates with constant amplitude and constant frequency. which feedback used in oscillators? +ve feedback 2. What is the output of an oscillator if transistor is ideal? Zero 3. what is Barkhausen criterion ? |AB| = 1,
9. what

are the various crystals? Rock salt, Quartz , Gallium Arsenide. 10. what are the advantages of crystal oscillators? Excellent frequency stability, high frequency operation and automatic amplitude control 11. which oscillators are AF oscillators? Audio frequency oscillators are RC phase shift and wein bridge oscillators 12. which are RF oscillators? Radio frequency oscillators are Colpitts, Hartley and crystal oscillators 13. why can't we use LC oscillator for low frequency oscillations? Because to produce low frequency oscillations the inductor value should be very high i.e no. of turns in inductor should be more so circuit becomes bulky POWER AMPLIFIERS: 1. What is the main difference between general amplifier and power amplifier? General amplifier can amplify voltage or current or both, but output power. power amplifier can increase the output power. 2. Why can't we get more current and voltage gains using general amplifier? In general amplifier voltage gain is more but current gain is less because as current increases heat dissipation increases across transistor increases so transistor will be burned. 3. Is the power amplifier amplifies the power of input signal? yes.4. What are the classifications of Power amplifiers? Basically 2 types: Audio power amp and Radio power amplifier. Based on mode of operation: Class A, Class B, Class AB, Class C, Class D. 5. Which power amplifier has more efficiency?

Class D6. Define efficiency? It is defined as ratio of output power and input power. 7. What are the efficiencies of various power amplifiers? Class A = 50% Class B = 78.5% Class C = 90% Class D = 100% 8. Define cross over distortion, and how it can be overcome? Due to the switching times of transistor a flat top occurs in output of Class B power amplifier. To avoid it the two transistors will normally be biased at a level that is slightly above cut-off.9. What are the percentage of active region in various Power amplifiers? Class A = 100% Class B = 50% Class AB = 50-100% Class C = less than 50% 10. What is total harmonic distortion? It is the ratio of the sum powers of all harmonic components to power of the fundamental frequency. 11.Define power dissipation in power amplifiers? It is defined as product of collector current and voltage across collector and emitter. 12. Specify Q-point location on load line for different power amplifiers? Class A - Middle point DC load line Class B - on Vce axis on load line Class AB - nearer to Vce axis on load line Class C - down side of Vce axis on load line. 13. Where we can use Class A power amplifier? Low power amplifiers where efficiency is not important 14. Where we can use Class B power amplifier? Output power amplifiers. 15. Where we can use Class C power amplifier? Tuned RF amplifiers but can not used as audio amplifiers due to high distortion.

Question No. 01: What is gross error? Answer: These errors are mainly due to human mistakes in reading or in using instruments or error in recording observations. This error also occurs due to incorrect adjustment of instruments and computational mistakes these errors cannot treat mathematically. Question No. 02: What is the function of Attenuator in CRO? Answer: The voltage in input terminal of the vertical amplifier causes the beam to deflect off the CRT screen, is unite low in amplitude. So that high amplitude signals may be displayed, an attenuator network is placed between the vertical input terminals of the vertical amplifier. The main function of the attenuator is to reduce the amplitude of the vertical input signal before applying it to vertical amplifier. Question No. 03: What are the basic components of a CRO? Answer: CRO Circuit consists of following components: 1. Vertical deflection system 2. Horizontal deflection system 3. Synchronization circuit 4. Blanking circuit 5. Intensity modulation 6. Position control 7. Focus control 8. Cathode ray tube 9. Calibration circuit Question No. 04: What do you mean by a Voltage transformer? Answer: The transformers used for voltage measurement are called voltage or potential transformer. Question No. 05: What do you mean by Turns ratio of instrument transformer? Answer: It is the ratio of number of turns in secondary winding to the number of turns in primary winding of an instrument transformer. Question No. 06: What are the three major categories of error? Answer: Error may arise from different sources and are usually classified as: 1. Gross error 2. Systematic error 3. Random error Question No. 07: What is measurement? Answer: The process of determining the amount, degree, or capacity by comparison (direct or indirect) with the accepted standards of the system units being used. Question No. 08: What is the function of probe in CRO? Answer: The probe performs the very important function of connecting the test circuit to oscilloscope without altering, loading or otherwise disturbing the test circuit. Question No. 09: Which device is used for the source of emission of electrons in a CRT? Answer: A barium and strontium oxide coated cathode is used for the source of emission of electrons in a CRT. Question No. 10: What is the function of electron-gun used in CRT?

Answer: The source of focused and accelerated electrons beam is the electron gun. The electron gun emits electrons and forms them into a beam consist of a heater, a cathode, a grid, a pre-accelerating anode, a focusing anode and an accelerating anode. Question No. 11: What do you mean by a phase Angel of instrument transformer? Answer: The angle between secondary current and primary current of a current transformer is called phase angle of instrument transformer. Question No. 01: What do you mean by ratio correction factor of instrument transformer? Answer: It is the ratio of the transformation ratio to the nominal ratio of an instrument transformer. Question No. 12: What is accuracy of a measurement? Answer: The degree of exactness (closeness) of a measurement compared to the expected (desired) value. Question No. 13: Why Systematic errors occur? Answer: These error occur due to 1. Instrumental error 2. Environmental error 3. Observational error Question No. 14: What are the functions of different probes used in CRO? Answer: Direct Probe: direct probe avoids stay-pick up which may create problems when low level signals are being measured. It is used for low frequency or low impedance circuit. Isolation probe: Isolation probe is used in order to avoid the undesirable circuit loading effects of the shielded probe. Detector probe: when analyzing the response to modulated signals used in Communications equipment like AM, FM and TV receivers, the detector probe functions to separate the low frequency modulation component from the high frequency carrier. Question No. 15: What do you mean by a Current transformer? Answer: The transformers which are used for measurement of current is called current transformer. Question No. 16: What do you mean by Nominal ratio of instrument transformer? Answer: It is the ratio of rated primary winding current to the rated secondary winding current of an instrument transformer. Question No. 17: What is Resolution of a measurement? Answer: The smallest change in a measured variable to which an instrument will respond. Question No. 18: What are the reasons of instrumental error? Answer: The instrumental errors arise due to three main reasons: 1. Due to inherent shortcoming in the instrument 2. Due to misuse of the instruments 3. Due to loading effect of instrument Question No. 19: What is the function of electron-gun assembly used in CRT?

Answer: The electron gun assembly produces a sharply focused beam of electrons which are accelerated to high velocity .this focused beam of electrons strikes the fluorescent screen with sufficient energy to cause a luminous spot on the screen. Question No. 20: What do you mean by transformation ratio of instrument transformer? Answer: It is the ratio of primary winding current to the secondary winding current of an instrument transformer. Question No. 21: What is precision of a measurement? Answer: A measure of the consistency or repeatability of measurement, i.e. successive reading do not differ. Question No. 22: How many types of probe used in CRO? Answer: There are three types of probe used in CRO: 1. Direct probe 2. Isolation probe 3. Detector probe Question No. 23: What is Error of a measurement? Answer: The deviation of the change in output (response) of the instrument to a change of input or measured variable. Question No. 24: What are the types of instrument transformer? Answer: There are two types of instrument transformer: 1. Current transformer 2. Voltage transformer Question No. 25: What is Sensitivity of a measurement? Answer: The ratio of the change in output (response) of the instrument to a change of input or measured variable. Question No. 26: What do you mean by an instrument transformer? Answer: Transformer which is used with measuring instrument is called instrument transformers. Instrument transformer is used as a protection circuit of power system for the operation of over current, under voltage, Earth fault etc. Question No. 27: What is Cathode ray oscilloscope (CRO)? Answer: Cathode ray oscilloscope is an instrument used for display, measurement and analysis of waveforms and other phenomenon in electrical and electronic circuit. Question No. 28: What are the Advantages of instrument transformer? Answer: Advantages of instrument transformer are: 1. Instrument transformers are moderate in size and used for 5 A current and 100 to 200 V measurements. 2. Instruments using instrument transformer are low cost. 3. Replacement of damage parts is Easy. 4. The metering circuit is isolated the high voltage power circuit hence insulation and safety is assured for operation. 5. There is low power consumption in metering circuit.

Question No. 29: What is the function of aquadag in a CRO? Answer: An aquadag is used in a CRO to collect secondary emission electrons.

Question No. 01: What id difference between power and energy? Answer: Energy is defined as the capacity of a physical system to perform work. In the context of electric circuits, energy (w) is related to power by the following relationship p = vi =dw/dt So the difference is that power is the rate of change of energy. Question No. 02: What do you mean by Phasors? Answer: Addition of two out-of-phase sinusoidal signals is rather complicated in the time domain. An example could be the sum of voltages across a series connection of a resistor and an inductor. Phasors simplify this analysis by considering only the amplitude and phase components of the sine wave. Moreover, they can be solved using complex algebra or treated vectorially using a vector diagram. Question No. 03: What is Corkscrew Rule? Answer: As current flows along a wire, the magnetic field rotates in the direction of a corkscrew. Question No. 04: Differentiate between Kirchhoff’s First law and Kirchhoff’s Second law? Answer: Kirchhoff’s First law: The total current leaving a point on an electrical circuit = total current entering Kirchhoff’s Second law: The sum of the voltages round any circuit = net “IR” drop in the circuit Question No. 05: How to calculate Energy stored in an inductance? Answer: Energy stored =½ L I2 Joules, where L is in henries and I is in amps Question No. 06: What is a capacitor and what does it do? Answer: Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy. Instead, a capacitor stores energy in the form of an electrostatic field between its plates. Question No. 07: What is Current Divider Rule (CDR)? Answer: Current divider rule provides a useful relationship for determining the current through individual circuit elements that are connected in parallel. Question No. 08: What is Voltage Divider Rule? Answer: Voltage divider rule provides a useful formula to determine the voltage across any resistor when two or more resistors are connected in series with a voltage source. Question No. 09: What is Current? Answer: Current can be defined as the motion of charge through a conducting material. The unit of current is Ampere whilst charge is measured in Coulombs. Question No. 10: Could you measure Voltage in series? Answer: No, Voltage is always measured across (in parallel with) a circuit element.

Question No. 11: What is Kirchoff’s Current Law (KCL)? Answer: The algebraic sum of all the currents entering or leaving a node in an electric circuit is equal to zero. In other words, the sum of currents entering is equal to the sum of currents leaving the node in an electric circuit. Question No. 12: Define Super node? Answer: A super node exists when an ideal voltage source appears between any two nodes of an electric circuit. The usual way to solve this is to write KCL equations for both nodes and simply add them together into one equation ignoring the voltage source in question. However, this would mean one less equation than the number of variables (node voltages) present in the circuit. A constraint equation can be easily specified given by the magnitude of the ideal voltage source present between the nodes and the respective node voltages. The following example will help clarify this scenario. Question No. 13: What does Ampere turns shows? Answer: mmf A coil of N turns carrying a current I amps gives an mmf of NI ampere turns In a vacuum, a magnetizing force of 1 ampere turn / metre produces a magnetic field of 1.26 × 10-6 tesla. Question No. 14: What is the difference between an inductor and a capacitor? Answer: An inductor is a passive electrical device employed in electrical circuits for its property of inductance. An inductor can take many forms. A capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). Question No. 15: How does a capacitor store an electrical charge? Answer: Electrical Energy in Capacitor stores in Potential Charge form. The energy stored in a capacitor is almost entirely in the electric field produced between the plates. It takes energy from a battery or some other power source to move electrons to one of the plates and away from the other. Question No. 16: Define Ampere? Answer: The quantity of total charge that passes through an arbitrary cross-section of a conducting material per unit second is defined as an Ampere. Mathematically, I =Q/t or, Q = It Where, Q is the symbol of charge measured in Coulombs (C), I is the current in amperes (A) and t is the time in seconds (s). Question No. 17: Define Ohm’s Law for A.C (Alternating Current)? Answer: Everything else would remain same only the resistance will be replaced with Impedance, which is defined as the opposition to the flow of A.C. Question No. 18: What do you mean by dependent and independent voltage sources? Answer: In general, there are two main types of DC sources 1. Independent (Voltage and Current) Sources 2. Dependent (Voltage and Current) Sources

An independent source produces its own voltage and current through some chemical reaction and does not depend on any other voltage or current variable in the circuit. The output of a dependent source, on the other hand, is subject to a certain parameter (voltage or current) change in a circuit element. Herein, the discussion shall be confined to independent sources only. Question No. 19: Differentiate between Magnetic field and Magnetic Flux? Answer: Magnetic field is B = μ H where B is in tesla and H = 1.26 × 10-6 times ampere turns/metre MMF in a solenoid of N turns and current I mmf = (4 m / 10) N I Gilberts. Whereas Magnetic flux φ = B A where ø is in weber, B is in tesla and A is in square meters. Magnetic flux in a uniform closed magnetic circuit, length L meters and cross section A square meters is =1.26NItA × 10-6/ L weber. Question No. 20: Differentiate between Induced emf and Self inductance? Answer: Induced emf, E = - N dφ/dt where E is in volts, N is number of turns and dφ/dt is in Wb/sec. This equation is the foundation on which Electrical Engineering is based. Whereas Self Inductance E = - L dI/dt, where E is in volts, L is inductance in henneries and dI/dt is in amps/sec. Self inductance of a coil wound on a ring of permeability is L = 1.26 N2 μ A / S × 10-6 Henneries, where N is number of turns, A is cross sectional area in m2 and S meters is the length of the magnetic circuit. Experimental results for a coil of length S meters, diameter d meters and radial thickness t meters with at core indicate L = 3 d2 N2 / (1.2 d + 3.5 S + 4 t) micro Henneries. (t = 0 for a single layer coil). Question No. 21: What is the function of the capacitor? Answer: A capacitor (originally known as a condenser) is a passive two-terminal electrical component used to store energy electrostatically in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors (plates) separated by a dielectric (i.e. insulator). Question No. 22: Could you measure current in parallel? Answer: No, Current is always measured through (in series with) a circuit element. Question No. 23: State and define Ohm’s Law? Answer: It is the most fundamental law used in circuit analysis. It provides a simple formula describing the voltage-current relationship in a conducting material. Statement: The voltage or potential difference across a conducting material is directly proportional to the current flowing through the material. V∝I V = RI or I =V/R or R =V/I Where, the constant of proportionality R is called the resistance or electrical resistance, measured in ohms (Ω). Question No. 24: Briefly explain the purpose of Inductor in an electric circuit? Answer: An inductor is a piece of conducting wire generally wrapped around a core of a ferromagnetic material. Like capacitors, they are employed as filters as well but the most well known application is their use in AC transformers or power supplies that converts AC voltage levels. Question No. 25: What is Superposition Theorem? Answer: Superposition theorem is extremely useful for analyzing electric circuits that contains two or more active sources. In such cases, the theorem considers each source separately to evaluate the current through or voltage across a component. The resultant is given by the algebraic sum of all currents or voltages caused by each source acting independently. Superposition theorem can be formally stated as follows: “The current through or voltage across any element in a linear circuit containing several sources is the algebraic sum of the currents or voltages due to each source acting alone, all other sources being removed at that time.”

Question No. 26: What is Force on a conductor in a magnetic field? Answer: F = B I L Newtons, where B in tesla, I in amps and L in meters. Question No. 27: What is an inductor and what does it do? Answer: An inductor is a passive electronic component which is capable of storing electrical energy in the form of magnetic energy. Basically, it uses a conductor that is wound into a coil, and when electricity flows into the coil from the left to the right, this will generate a magnetic field in the clockwise direction. Question No. 28: At what base you will tell the direction of rotation of DC Motors and Generators? Answer: Motors obey the left hand rule and generators the right hand rule. Question No. 29: What is the difference between Voltages or Potential Difference? Answer: Voltage or potential difference between two points in an electric circuit is 1V if 1J (Joule) of energy is expended in transferring 1 C of charge between those points. It is generally represented by the symbol V and measured in volts (V). Note that the symbol and the unit of voltage are both denoted by the same letter; However, it rarely causes any confusion. The symbol V also signifies a constant voltage (DC) whereas a time-varying (AC) voltage is represented by the symbol v or v (t) Question No. 30: What does the term “Voltage Regulation” means? Answer: Voltage regulation (VR) is an important measure of the quality of a source. It is used to measure the variation in terminal voltage between no load (IL =0, open circuit) and full load (IL = IFL) Question No. 31: State and define Norton’s Theorem? Answer: Thevenin’s equivalent circuit is a practical voltage source. In contrast, Norton’s equivalent circuit is a practical current source. This can be formally stated as: “Any two-terminal, linear circuit, of resistors and sources, can be replaced by a single current source in parallel with a resistor.” To determine Norton’s equivalent circuit, Norton current, IN, and Norton resistance, RN , are required. The following steps outline the procedure required: 1. Remove the load resistance, RL. 2. IN is the SC current through the load terminals and 3. RN is the resistance across the load terminals with all sources replaced by their internal resistances. Clearly RN = RTH. Question No. 32: What does the term Power Factor shows? Answer: The term cos φ is called the power factor and is an important parameter in determining the amount of actual power dissipated in the load. In practice, power factor is used to specify the characteristics of a load. For a purely resistive load φ = 0 Degree, hence Unity Power Factor For a capacitive type load I leads V, hence Leading power factor For an inductive type load I lags V, hence Lagging power factor Clearly, for a fixed amount of demanded power P, at a constant load voltage V, a higher power factor draws less amount of current and hence low I2R losses in the transmission lines. A purely reactive load where φ → 900 and cos φ → 0 will draw an excessively large amount of current and a power factor correction is required. Question No. 33: What is the energy stored in the magnetic field of the inductor? Answer: The formula for the energy stored in a magnetic field is E = ½ LI 2. The energy stored in a magnetic field is equal to the work needed to produce a current through the inductor. Energy is stored in a magnetic field. Question No. 34: What is the function of Capacitor in Electrical Circuits? Answer: A capacitor is a passive circuit element that has the capacity to store charge in an electric field. It is widely used in electric circuits in the form of a filter.

Question No. 35: What is DC Current source? Differentiate between ideal and non-ideal current sources Answer: A current source, unlike the DC voltage source, is not a physical reality. However, it is useful in deriving equivalent circuit models of semiconductor devices such as a transistor. It can also be subdivided into ideal and non-ideal categories. The Ideal Current Source By definition, an ideal current source that produces a current which is independent of the variations in load. In other words the current supplied by an ideal current source does not change with the load voltage. Non-Ideal or Practical Current Source The current delivered by a practical current source falls off with an increase in load or load voltage. Question No. 36: What does the term Super-mesh means? Answer: A super-mesh exists when an ideal current source appears between two meshes of an electric circuit. In such a situation, like super-node, mesh equations are written for the meshes involved and added giving a single equation. Again, there would be one less equation than the number of variables (mesh currents) and hence a constraint equation is needed. This would be based on the magnitude of the ideal current source present between the two meshes and their mesh currents. Question No. 37: How to calculate Energy stored in a capacitance? Answer: Energy stored = ½ C V2 Joules, where C is in farads and V in volts Question No. 38: How many Types of Circuit Loads are there in a Common Electrical Circuit? Answer: A load generally refers to a component or a piece of equipment connected to the output of an electric circuit. In its fundamental form, the load is represented by any one or a combination of the following: 1. Resistor (R) 2. Inductor (L) 3. Capacitor (C) A load can either be of resistive, inductive or capacitive nature or a blend of them. For example, a light bulb is a purely resistive load where as a transformer is both inductive and resistive. A circuit load can also be referred to as a sink since it dissipates energy whereas the voltage or current supply can be termed as a source. Question No. 39: Differentiate between ideal and non-ideal voltage sources? Answer: The Ideal Voltage Source An ideal voltage source which has a terminal voltage which is independent of the variations in load. In other words, for an ideal voltage source, the supply current alters with changes in load but the terminal voltage, VL always remains constant. Non-Ideal or Practical Voltage Source For a practical source, the terminal voltage falls off with an increase in load current. Question No. 40: What is the method to solve circuit using Source Transformation? Answer: In an electric circuit, it is often convenient to have a voltage source rather than a current source (e.g. in mesh analysis) or vice versa. This is made possible using source transformations. It should be noted that only practical voltage and current sources can be transformed. In other words, a Thevenin’s equivalent circuit is transformed into a Norton’s one or vice versa. The parameters used in the source transformation are given as follows. Thevenin parameters: VTH, RTH =⇒ RN = RTH, IN = VTH/RTH Norton parameters: IN, RN =⇒ RTH = RN, VTH = RN IN Any load resistance, RL will have the same voltage across, and current through it when connected across the terminals of either source. Question No. 41: Differentiate between Real and Apparent Power?

Answer: It is important to highlight that in AC circuits, the product of voltage and current yields the apparent power which is measured in volt-amperes or VA KW which is also written ad Kilo-Watt is the real power that is actually converted to the useful work. KVAR is also termed as Kilo-Volt Reactive this power is used for magnetic field excitation and flows back and forth between source and load. Question No. 42: At what factor Resistance R of a conductor depends? Answer: R = p L (1 + αT) / A ohms where p is resistivity in ohms per cm cube, L cm is the length, A in cm2 is the cross sectional area, α is temp coefficient and T is the temperature in degrees Celsius. Several sources give Copper p = 1.7 × 10-6 ohms per cm cube and α = 0.004. At very low Temperatures, the resistance of some materials falls to zero Question No. 43: Why Inductors are installed in electrical Circuits? Answer: An inductor is a piece of conducting wire generally wrapped around a core of a ferromagnetic material. Like capacitors, they are employed as filters as well but the most well known application is their use in AC transformers or power supplies that converts AC voltage levels. Question No. 44: What is Maximum Power Transfer Theorem? Answer: As discussed in the section on Thevenin’s theorem, any DC network of sources and resistances can be replaced by a single voltage source in series with a resistance connected across the load: The maximum power transfer theorem states that the power delivered to the load is maximum when the load resistance, RL is equal to the internal (source) resistance, Rs of the DC power supply. In other words, it can be said that the load resistance must match the Thevenin’s resistance for maximum power transfer to take place i.e., (Rs = RTH) = RL When this occurs, the voltage across the load resistance will be Vs/2 and the power delivered to the load is given by which clearly demonstrates maximum power delivered when Rs = RL. Under this condition, the maximum power will be: Question No. 45: What does Bode Plots shows? Answer: Bode plots are graphical ways to display the behavior of a circuit over a wide range of frequencies. By plotting the amplitude and phase versus the logarithm of frequency, each unit of change on the ω axis is equal to a factor of 10 also called a decade of frequency. Also, there may be a wide distribution in the amplitude response over a specified range of frequencies. The usual way is to plot the amplitude in dB and phase in degrees or radians versus the logarithm of frequency. Question No. 46: Elaborate Thevenin’s Theorem? Answer: Thevenin’s theorem provides a useful tool when solving complex and large electric circuits by reducing them to a single voltage source in series with a resistor. It is particularly advantageous where a single resistor or load in a circuit is subject to change. Formally, the Thevenin’s theorem can be stated as: “Any two-terminal linear electric circuit consisting of resistors and sources can be replaced by an equivalent circuit containing a single voltage source in series with a resistor connected across the load.” The following steps outline the procedure to simplify an electric circuit using Thevenin’s theorem where VTH and RTH are the Thevenin’s voltage and Thevenin’s resistance respectively. 1. Remove the load resistance RL. 2. VTH is the open circuit (OC) voltage across the load terminals 3. RTH is the resistance across the load terminals with all sources replaced by their internal resistances. Question No. 47: Differentiate between Low Pass, High pass and Band Pass filter? Answer: Filters form a vital part in electrical networks especially where a particular frequency range is of prime concern. For instance, a radio station is broadcasting a transmission at a frequency of 100 MHz. This means that it is required to design a receiving filter which allows only 100 MHz frequency to pass through whilst other frequencies are filtered out. An ideal filter will attenuate all signals with frequencies less than and greater than 100 MHz thus providing the best channel sound quality without any distortion.

Low Pass Filter: A low pass Filter allows low frequencies to pass through the circuit whereas high frequencies are severely attenuated or blocked. High Pass Filter: A high pass filter, as the name suggests, allows high frequencies to pass through the circuit whilst low frequencies are attenuated or blocked. The cut-off point or bandwidth concept is the same as in the low pass filter. Band Pass Filter: A band pass filter permits a certain band of frequencies to pass through the network which is adjusted by the designer. It is simply an amalgamation of a low pass and a high pass filter. Question No. 48: Distinguish between self-induction and mutual induction. Answer: Self-Induction 1. Self-Induction is the characteristic of the coil itself. 2. When the main current in the coil decreases, the induced current opposes the decay of current in the coil. 3. When the main current in the coil increases, the induced current opposes the growth of current in the coil. Mutual induction 1. Mutual induction is the characteristic of a pair of coils. 2. When the main current in the coil decreases, induced current developed in the neighboring coil opposes the decay of current in the coil. 3. When the main current in the coil increases, the induced current developed in the neighboring coil opposes the growth of current in the coil

Question No. 01: What is mathematical model of a control system? Answer: Control system is a collection of physical elements connected together to serve an objective. The output and input relations of various physical systems are governed by differential equations. Mathematical model of a control system constitutes set of differential equations. The response of the output of the system can be studied by solving the differential equations for various input conditions. Question No. 02: What is Zero of the system? Answer: Zero of a function F(s) is a value at which the function F(s) becomes zero, where F(s) is a function of complex variable s. Question No. 03: What is Time response of the control system? Answer: Time response of the control system is defined as the output of the closed loop system as a function of time. Time response of the system can be obtained by solving the differential equations governing the system or time response of the system can also be obtained by transfer function of the system. Question No. 04: Explain Mechanical Translational System? Answer: Model of mechanical translational system can be obtained by using three basic elements Mass, spring and Dash-pot. Weight the mechanical system is represented by mass and is assumed to be concentrated at the center of body The elastic deformation of the body can be represented by the spring Friction existing in a mechanical system can be represented by dash-pot. Question No. 05: What is Signal Flow Graph? Answer: A Signal Flow Graph is a diagram that represents a set of simultaneous linear algebraic equations. By taking Laplace transform the time domain differential equations governing a control system

can be transferred to a set of algebraic equations in s-domain. The signal Flow graph of the system can be constructed using these equations. Question No. 06: How Time response of the system is divided? Answer: Time response of the system consists of two parts: 1. Transient state response 2. Steady state response. Transient response of the system explains about the response of the system when the input changes from one state to the other. Steady state response of the system shows the response as the time t, approaches infinity Question No. 07: What is Order of the system? Answer: Order of the system is defined as the order of the differential equation governing the system. Order of the system can be determined from the transfer function of the system. Also the order of the system helps in understanding the number of poles of the transfer function. For nth order system for a particular transfer function contains ‘n’ number of poles. Question No. 08: What are Test signals and their significance? Answer: The knowledge of the input signal is required to predict the response of the system. In most of the systems input signals are not known ahead of the time and it is also difficult to express the input signals mathematically by simple equations. In such cases determining the performance of the system is not possible. Test signals helps in predicting the performance of the system as the input signals which we give are known hence we can see the output response of the system for a given input and can understand the behavior of the control system. The commonly used test signals are impulse, ramp, step signals and sinusoidal signals. Question No. 09: What is Pole of the system? Answer: Pole of a function F(s) is the value at which the function F(s) becomes infinite, where F(s) is a function of the complex variables. Question No. 10: What is S-domain and its significance? Answer: By taking Laplace transform for differential equation in the time domain equations in S-domain can be obtained. L{F(t)}=F(s) S-domain is used for solving the time domain differential equations easily by applying the Laplace for the differential equations. Question No. 11: What are the basic properties of Signal Flow Graph? Answer: The basic properties of the signal flow graph are:  Signal Flow Graphs are applicable to linear systems  It consists of nodes and branches. A node is a point representing a variable or signal. A branch indicates the functional dependence of one signal on another  A node adds the signals of all incoming branches and transmits this sum to all outgoing branches  Signals travel along branches only in a marked direction and is multiplied by the gain of the branch The algebraic equations must be in the form of cause and effect relationship