Notesch # 19

Chapter # 19

Electronics Q#1: Choose the correct answer of the statement from the given choices I.

Electronics deals with the principles and ways by means of which we control the flow of _______ (a) Electrons (b) Protons (c) Neutrons (d) Ions

II.

Analogue electronics deals with the ________________Quantities. (a) Continuously varying (b) constant (c) rapidly varying (d) physical

III.

ADC is an abbreviation of ____________ (a) Analogue to Digital Converter (b) Analogue Device control (c) Any Digital Converter (d) Any Digital Controller

IV.

DAC stands for (a) Digital to Analogue Converter (b) Device for the Amplification Control (c) Device of Analogue Communication (d) Data Analyzer and Controller

V.

Conductors are those materials which have an access of _____________ (a) Electrons (b) Protons (c) Neutrons (d) Ions

VI.

Insulators are those materials which have ___________ of electrons. (a) Access (b) Shortage (c) Deficiency (d) Leakage

VII.

The process of adding impurity in a growing semi-conductor to modify its conductivity is (a) Rectification (b) Doping (c) Ionization (d) Crystallization

VIII.

When a trivalent impurity is added to semi-conductor then material is known as (a) N-type (b) M-type (c) P-type (d) Q-type

IX.

When a pentavalent impurity is added to semi-conductor then material is known as (a) N-type (b) M-type (c) P-type (d) Q-type

X.

When a pentavalent impurity is added to semi-conductor then number of ________ will increase in it. (a) Electrons (b) Protons (c) Neutrons (d) holes

XI.

When a trivalent impurity is added to semi-conductor then number of ________ will increase in it. (a) Electrons (b) Protons (c) Neutrons (d) holes

XII.

Semi-conductors (Silicon and Germanium) belong to ________ group of periodic table (a) Third (b) Forth (c) Fifth (d) Sixth

XIII.

Semi-conductors (Silicon and Germanium) have _______ free electrons. (a) 5 (b) 4 (c) 3 (d) 6

XIV.

In an N-type semi-conductor _______ are majority carriers. (a) Electrons (b) Protons (c) Neutrons (d) holes

XV.

In an N-type semi-conductor _______ are majority carriers. (a) Electrons (b) Protons (c) Neutrons (d) holes

XVI.

N-type materials have a __________ net charge. (a) positive (b) Negative (c) Zero (d) All of these

XVII.

P-type materials have a __________ net charge. (a) Positive (b) Negative (c) Zero (d) All of these

XVIII.

_________ are immovable in every crystal. (a) Electrons (b) Protons (c) Neutrons (d) holes

XIX.

When anode of diode is connected to the positive terminal and cathode to the negative terminal of the battery the diode is said to be ___________ biased. (a) Forward (b) Reverse (c) Auto (d) Manual

XX.

The process of converting an alternating current to direct current is (a) Rectification (b) Doping (c) Ionization (d) Crystallization

XXI.

The device used to convert an alternating current to direct current is called _________ (a) Diode (b) Polarizer (c) Rectifier (d) ADC

XXII.

In a rectifier the current is ___________ directional. (a) Uni (b) Poly (c) Multi (d) None of these

XXIII.

Collector current is many times greater than the _________current. (a) Base (b) Emitter (c) Both a & b (d) None of these

XXIV.

Digital electronics deals with two variables called_____________ variables. (a) Langrangian (b) Boolean (c) Estonian (d) Algebraic

XXV.

AND operation is represented by (a) + (b) * (c) . (d) X

XXVI.

OR operation is represented by (a) + (b) * (c) . (d) X

XXVII.

NOT operation is represented by (a) + (b) * (c) – (bar) (d) X

XXVIII.

In house safety alarm ________ gate is used. (a) AND (b) OR (c) NOT (d) Any

Q#2: Give short answer of the following questions I.

Define Electronics?

Ans: It is the branch of applied Physics which discusses those principles and ways by means of which we can control the flow of the electrons, using different semi-conductor devices. II.

Which is the largest achievement of electronics?

Ans: The biggest achievement of electronics is computer, which has taken the whole world into its grip. III.

How many branches of electronics are there?

Ans: There are basically two types of electronics i.e. Analogue electronics and Digital electronics. IV.

Define Analogue Quantities?

Ans: Those quantities whose value vary continually or remain constant are called analogue quantities e.g. Temperature, Time, Pressure, Distance etc V.

Define Digital quantities?

Ans: Those quantities whose value vary rapidly or between two different states are called Digital quantities e.g. . VI.

Define Analogue electronics?

Ans: The part of electronics consisting of such circuits which processes analogue quantities is called analogue electronics. VII.

Define Digital electronics?

Ans: The part of electronics which Provides the data in the form of a maximum and minimum voltage signal is known as digital electronics. VIII.

How electronic sound systems work?

Ans: The mouth piece (microphone) converts the sound into a continuously varying electrical signal (Potential), which is fed in an amplifier and amplifier amplifies that signal without changing its shape to such an extant that we want then it is provided to an earphone (speaker) which convert this electrical signal into sound? IX.

Write down the applications of electronics?

Ans: The use of electronics is not only limited to computer only but it is very widely used in modern Telephone system, Radar system, Naval and other systems of military Importance, Devices to control the operation of industrial machines, Medical equipments and many Household appliances.

X.

Define an analogue to Digital converter?

Ans: A circuit which converts the analogue signal into a digital signal is called analogue to digital converter (ADC). XI.

How can we process an analogue signal by using a digital circuit? OR

What is the application of analogue to digital convertor? Ans: By using an analogue to digital convertor we can process an analogue signal with a digital circuit. XII.

Define a digital to analogue convetor?

Ans: A circuit which converts the digital signal into an analogue signal is called digital to analogue convertor (DAC). XIII.

How many types of materials are there according to their conductivity?

Ans: There are three types of materials according to their conductivity i.e. (a) Conductors (b) Semi- conductors (c) Non- conductors XIV.

Define conductor?

Ans: Those substances through which electric current and heat can pass easily are called conductors. OR Those materials which have an access of free electrons per unit volume are called conductors. XV.

Define Semi-conductors?

Ans: Those substances through which electric current and heat, can pass under some conditions and can’t pass under some other conditions called Semi-conductors. OR

Those materials which have not, as much access of free electrons per unit volume that current can pass through them are called Semi-conductors. XVI.

Define Non-conductors (Insulators)?

Ans: Those substances through which electric current and heat can’t pass easily are called non-conductors. OR Those materials which have not an access of free electrons per unit volume are called non-conductors.

XVII.

Define Hole in a semi-conductor?

Ans: The vacancy of an electron in the crystal of a semi-conductor is called Hole and it should always be considered as a positive charge in the semi – conductor electronics. XVIII.

Can semi-conductor could behave as a Non-conductor?

Ans: Yes! A crystal of semi-conductor in its pure form at zero Kelvin behaves as a non-conductor. XIX.

What happens whenever a covalent bond breaks in the crystal of Semi-conductor?

Ans: Whenever a covalent bond breaks it creates an electron-hole pair in the structure. XX.

Why a semi-conductor so called?

Ans: Because the number of free electrons and holes present in it (Semiconductor) is much smaller than the number of free electrons in the conductor. XXI.

Define Doping?

Ans: The process of adding a specific amount of a trivalent or pentavalent material as Impurity during the growth of the crystal of Semi-conductor is called doping. XXII.

How many types of doped semi conductors are there?

Ans: There are basically two types of doped crystals i.e. (a) N-type Material (b) P-type Material XXIII.

Define N-type Material?

Ans: When a pentavalent Impurity is added to the pure semi-conductor crystal during its growth, then the new doped material is called N-type semi-conductor.

OR The doped semi-conductor having access of electrons is called N-type semiconductor. XXIV.

Define P-type Material?

Ans: When a trivalent Impurity is added to the pure semi-conductor crystal during its growth, then the new doped material is called P-type semi-conductor. OR The doped semi-conductor having access of Holes is called P-type semiconductor. XXV.

What do you mean by trivalent impurity?

Ans: The elements of the third group of the periodic table used for the doping are called trivalent impurity. OR The elements having three electrons (free electrons) in its outer most orbits are called trivalent impurity. XXVI.

What do you mean by pentavalent impurity?

Ans: The elements of the fifth group of the periodic table used for the doping are called pentavalent impurity. OR The elements having five electrons (free electrons) in its outer most orbits are called pentavalent impurity.

XXVII.

What is the net charge of N-type and P-type semi-conductor materials?

Ans: The net charge of the net charge of N-type and P-type semi-conductors materials is zero. OR The N-type and P-type material s are overall neutral. XXVIII.

Why N and P-type materials are neutral?

Why the net charge of doped semi-conductor material is zero? Ans: Because the total number of electrons and protons in whole crystal remains same during doping, so the net charge of the doped material remains zero. Even the material has an access or deficiency of an electron, access or

deficiency is not in the atom but in the bond of the crystal. Which when fills then the crystal will acquire any charge. OR Because of the imbalance-mint of the electrons in the crystal structure. XXIX.

Define PN-junction?

Ans: If a crystal of silicon or germanium is doped in such a way that its one part becomes N-type and the other P-type then a junction would be formed in between which is known as PN-junction. XXX.

Define depletion region?

Ans: The region in which potential barrier is set up is called Depletion region. XXXI.

Define potential barrier?

Ans: The potential difference produced between two ends of a PN-junction is called potential Barrier, and is so called because it stops the further flow of electrons from N-type to P-type.

XXXII.

Which are the majority carriers in the N-type materials?

Ans: Free electrons of the bond are the majority carriers in the N-type Materials. XXXIII.

Which are the majority carriers in the P-type materials?

Ans: Holes of the bond are the majority carriers in the N-type Materials. XXXIV.

Whether electrons can change there orbit or not during the formation of PN-junction or not?

Ans: No! the electrons could not change the energy level (orbit) during the formation of PN-junction. So we can say that they remain in their respective orbits during this formation. XXXV.

Whether the positive ions present in the semi-conductor material are moveable or not.

Ans: NO! In a semi-conductor crystal, every ion has a fixed position and it could not move from its position. XXXVI.

What happens in the crystal of semi-conductor after the formation of PN-junction?

Ans: after the formation of PN-junction, some of the electrons from N-type region cross the junction and enter into the P-type region, where the holes are in abundance, and fill up holes present close to the junction, Until a barrier will form and stop the further flow.

XXXVII.

What is the value of potential barrier in the case of silicone?

Ans: The value of potential barrier is 0.7eV in case of silicone. XXXVIII.

What is the value of potential barrier in the case of germanium?

Ans: The value of potential barrier is 0.3eV in case of germanium. XXXIX.

Define a semi conductor diode?

Ans: An enveloped PN-junction in a glass or metallic case is called semiconductor diode. XL.

Name the terminals of a semi conductor diode?

Ans: A semi-conductor diode has two terminals named as (a) Anode (b) Cathode XLI.

Whether current can flow or not, through a diode under ordinary conditions? And why?

Ans: The current could not flow through the diode under ordinary conditions, due to the presence of potential barrier in it. Which will vary with the applied voltage? XLII.

What are the conditions of forward bias of a diode?

Ans: There are two conditions for the forward bias of a diode (a) the anode should be connected to the positive terminal and the cathode to the negative terminal of the battery. (b) the potential of the battery should be greater than the potential barrier of the diode, so that charge carriers could pass through it for the flow of current. XLIII.

Define biasing of a diode?

Ans: Biasing is a process during which the terminals of diode are connected to the battery. There are two types of biasing (a) forward biasing (b) reverse biasing XLIV.

Define the forward biasing of the diode?

Ans: when the anode of a diode is connected to the positive terminal and cathode to the negative terminal of the battery and current flows through the diode, then the biasing is known as the forward biasing of the diode. OR When the depletion region of the diode decreases due to biasing, then such a biasing is called forward biasing. XLV.

Define the reverse biasing of the diode?

Ans: when the anode of a diode is connected to the negative terminal and cathode to the positive terminal of the battery and current does not flow through the diode, then the biasing is known as the forward biasing of the diode. OR When the depletion region of the diode increases due to biasing, then such a biasing is called reverse biasing. XLVI.

Define Rectification?

Ans: The process of converting an alternating current into a direct current is known as rectification. XLVII.

Why we need rectification?

Ans: Ordinarily electricity is provided to us in the form of alternating current but most of the electronic devices operate by direct current, therefore it becomes necessary that we convert it. XLVIII.

Which circuit converts an alternating current to a direct current?

Ans: Electronic circuit which converts an alternating current to a direct current is called Rectifier. OR Rectifier is an electronic device which converts an alternating current to the direct current. XLIX.

Define a Transistor?

Ans: A transistor is an electronic device which has one (P or N) type of semiconductor material sandwiched between the opposite (N or P) type of semiconductor material. L.

Define an npn-transistor?

Ans: If a crystal of germanium or silicon is doped in such a way that two N-type regions are formed at the ends while a very thin layer of P-type material is formed between them, then the finally formed crystal is known as NPNtransistor. LI.

Define a pnp-transistor?

Ans: If a crystal of germanium or silicon is doped in such a way that two P-type regions are formed at the ends while a very thin layer of N-type material is formed between them, then the finally formed crystal is known as PNP-transistor. LII.

Name the different terminals of a transistor?

Ans: A transistor normally has three terminals named as (a) Emitter (b) Base (c) Collector LIII.

Name the different junctions formed in a transistor?

Ans: In a transistor normally two junctions formed named as (a) Emitter-Base junction (b) Base- Collector Junction LIV.

What is the condition of bias for the working of a transistor?

Ans: For the working of a transistor generally emitter base junction is forward bias and the base-collector junction is reverse biased. LV.

What is the distribution of current in a transistor?

Ans: The total value of current in a transistor is equal to the amount of current passing through the emitter, and this current further divided between collector and base. So we can write it as

IE = IC + IB LVI.

Which one (base or collector) current is greater?

Ans: The collector current is many times greater than the Base current. LVII.

How many states a digital circuit could have?

Ans: Normally a digital electronic circuit has only two states (any of them) (a) ON or OFF (b) TRUE or FALSE (c) RIGHT or WRONG (d) OPEN or CLOSE LVIII.

Define Boolean Variables?

Ans: The things which can have only two possible states are known as Boolean variables and these are normally represented by 0 and 1. LIX.

What are the basic operations of Digital electronics?

Ans: Digital electronics is based on three types of operations known as (a) AND operation (b) OR operation (c) NOT operation LX.

Define the AND operation?

Ans: We can define AND operation to be that in which the output has a value 1 only when both of the inputs are 1. And the output has a value 0 when any of the inputs is 0. LXI.

Define the OR operation?

Ans: We can define OR operation to be that in which the output has a value 0 only when both of the inputs are 0. And the output has a value 1 when any of the inputs is 1. LXII.

Define the NOT operation?

Ans: We can define NOT operation to be that in which the output has a value opposite to the input. LXIII.

Define AND gate?

Ans: The electronic circuit which implements truth table of the AND operation is known as AND-gate. LXIV.

Define OR gate?

Ans: The electronic circuit which implements truth table of the OR operation is known as OR-gate. LXV.

Define NOT gate?

Ans: The electronic circuit which implements the truth table of the NOT operation is known as NOT-gate. LXVI.

What happens to the Boolean variables after NOToperation?

Ans: A Boolean variable after NOT operation changes its state and acquires the other possible state. LXVII.

Define NAND gate?

Ans: A NAND gate is formed by the combining of a NOT gate with the output terminal of AND gate. LXVIII.

Define NOR gate?

Ans: A NOR gate is formed by the combining of a NOT gate with the output terminal of OR gate.

Long Questions Q#3: Write a note on the formation of N-type and P-type semi conductors ? Q#4: (a) Explain the formation and construction of a PN-junction?

(b) Explain the process of formation of potential barrier and depletion region? Q#5: (a) Write down the working of a diode under forward and reverse bias? (b) Write down the process of rectification by using a diode? Q#6: Explain the operation of a transistor? Q#7: Explain the AND operation with the help of an example? Q#8: Explain the OR operation with the help of an example? Q#9: Explain the NOT operation with the help of an example? Q#10: Explain the working operation of a house safety alarm?