Bab 9

CHAPTER 9: ELECTRONIK

2.

1. Diagram 4.1 shows the use of a transistor in a circuit.

Bulb

R1 = 1500 Ω IB R2

V2

IC

6V

Figure 6 (i)

IE DIAGRAM 4.1

(a) Name the type of transistor used. ..………..……………………………………………..…………… [1 mark] (b) The transistor is switched on when the base voltage V2 ≥ 2 V. (i)

Write an equation to show the relationship between IB, IC and IE.

(ii)

………………………………………..…………………… [1 mark] Calculate the minimum value of R2 when the transistor is switched on.

Figure 6 (ii) Figures 6 (i) and 6(ii) show circuits used to produce full-wave rectification. Four diodes, A,B,C and D are arranged to form a bridge rectifier. a) Which diode will conduct current when an AC current is flowing i) forward ……………………………………………………………… ( 1 mark ) ii) backward ……………………………………………………………… ( 1 mark ) b) Describe the directions of the AC current passing through the resistor ………………………………………………………………… ( 1 mark) c) In the space below draw the signals that can be seen on the screen of a cathode ray oscilloscope for

[2 marks]

i) an AC input

(c) The resistor R2 is then replaced with a light dependent resistor which has a high resistance when it is dark. (i)

(2 marks )

Explain whether the bulb will light up during the day. ii) the output without the capacitor

.....................……………………………………… …………………

(2 marks )

iii) Output with a capacitor

....…………………………………………………………………….. [2 marks] (ii) Besides being used as a switch, state one other use of a transistor.

(2 marks )

...…………………………………………………………………….. [1 mark]

d) What is the function of a rectifier in an electric circuit ? ………………………………………………………………… ( 1 mark )

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3. Diagram 7.1 shows a transistor circuit with a bulb L.

(e)

........................................................................................................... ........................................................................................................... [1 mark] An automatic fire alarm is needed to emit sound in case of fire. Suggest two modifications that have to be made to the circuit in Diagram 7.1 by replacing the components with suitable electronic components. ........................................................................................................... .

........................................................................................... [2 marks] 4. Diagram 7.1 shows a circuit consisting of 3 logic gates AND, OR and NOT .

DIAGRAM 7.1 (a) Name the type of transistor shown in Diagram 7.1. .................................................................................................... [1 mark] (b) Based on Diagram 7.1: (i) What is the potential difference across point X and point Z? (ii)

(a)

........................................................................................... [1 mark] What is the total resistance between point X and point Z?

What is meant by logic gate?

………………………………………………………………....[1mark] (b) Diagram 7.2 shows a type of switch.

............................................................................................. [1 mark] Using the answers from (b)(i) and b(ii), calculate the potential difference across YZ.

(iii)

DIAGRAM 7.2 By using one or two of the the switch above and suitable connecting wires, complete the circuit in the diagrams below to produce, (i) AND gate

[2 marks]

(c) State what will happen to the lamp,L, if the base-emitter potential difference, VBE is 2 volts? Explain your answer. ...................................................................................................................

(d)

................................................................................................. [2 marks] Without adding any new component to Diagram 7.1, what modification is needed so that the opposite situation than the one in 7(c) occur at lamp L.

(ii)

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OR gate

[1mark] (e)

(iii)

NOT gate

Ahmad would like to construct a logic gate circuit to switch on an air conditioner in his house automatically. He has chosen a light- sensitive device to detect daytime and night and heat-sensitive device to detect the surrounding temperature. He has constructed a truth table as shown below. Input P Input Q Output R Night - 0 Cold - 0 Off - 0 Night - 0 Hot - 1 On - 1 Day - 1 Cold - 0 On - 1 Day - 1 Hot - 1 On - 1 You are given the logic gate such as OR, AND and NOT. Complete the logic gate circuit to help Ahmad to make his air conditioner functions as the situation above.

[3 marks]

(c )

Diagram 7.2 below shows the combination of two NAND gates. The combination will produce a single gate M

(i)

(i)

(d)

DIAGRAM 7.2 Complete the truth table in table 7.1 below for the combination of two NAND gates. K L M 0 0 0 1 1 0 1 1 [1mark] Name the logic gate M.

5.

[3 marks] Diagram 8.1 shows a component used to observe current flow through a Semiconductor diode in forward bias.

……………………………………………………………………… [1mark] Draw a combination of two NOR gates to produce a single gate OR.

DIAGRAM 8.1 (i) State one function of a diode.

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……………………………………………………… [1 mark] (ii) Complete the circuit to light up the bulb.

……………………………………… ………………………………… …………………………………………………… …………………… [3

[2 mark] (iii) The bulb will light up in forward bias. Explain.

marks]

…………………………………………………………………………… …………………………………………………………………… ……… [2 mark] (a) Circuit X consist an electronic component connected between transformer, resistance R and cathode ray oscilloscope .Input and output result as shown in the Diagram 8.2.

Input

6.

Diagram 6.1 shows a circuit to investigate the working principle of a transistor. The rheostat R is adjusted to get a set of data of the microammeter reading , I1 and the miliammeter reading, I2. .Table 6 shows the reading of I1 and I2.

Output

Circuit X R DIAGRAM 6.1 I1 / μA 0.0 0.5 1.0 1.5 2.0 2.5 TABLE 6

DIAGRAM 8.2

(i) Draw a schematic diagram for circuit X in Diagram 8.2.

[3 marks]

(ii) A capacitor is connected parallel to R. Trace the pulsing current from circuit X

(a)

I2 / mA 0.0 0.2 0.4 0.6 0.8 1.0

Name the current (i) I1 ……………………………………………………………………………….…………… ………………

[1 mark ] (ii)

I2

…………….………………………………………………………………………………………………

[1 mark] (iii)

(b) Explain how capacitor changes varying d.c. to smoothened d.c.?

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[1 mark] Using Table 6, state two observations about the value of I1 and I2

……………………………………………………………………………………

(b) Diagram 7.2 shows a transistor circuit.

… …………………………………………………………………………………… … [ 2 marks ] (c)

Based on your answer in (b) state the function a transistor.

………………………………………………………………… [ 1 mark ] (d)

Diagram 7.1

The battery P is removed and replaced by two resistors.

When the sliding contact X is at the 0 V end of the potentiometer, (i) is there any current flow through the base and emitter circuit? ………………………………………………………………………………. ………………………………………………………………………[1 mark] (ii) what happened to the transistor and the bulb? Tick in the box

(i) Complete the circuit in Diagram 6.2 to ensure the transistor workable without battery P.

[1 mark] (iii) If the sliding contact X were raised from 0 V end to the 3 V end of the potentiometer, what happened to the bulb? Explain your answer ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………[2 marks] (c) Diagram 7.3 shows a transistor is used to light up during the day.

Diagram 6.2 [ 2 marks ] (ii)

State the function of the two resistors. [1

..………………………………………………………………………………………………

mark ] 7. Diagram 7.1 shows a semiconductor transistor.

Diagram 7.2 Diagram 7.3 (i) Suggest a modification to light up the lamp at night. ……………………………………………………………………………….

(a) (i) Name the type of the transistor. …………………………………………………………………… [1 mark] (ii) Transistor has three terminals connected to the emitter, base and collector. Label the emitter, base and collector in Diagram 7.1 [1 mark]

………………………………………………………………… [1 mark] (ii) A student replaced lamp L with a lamp labeled 240 V 24 W in Diagram 7.3.

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The bulb is not light up. (a) Why the lamp is not light up?

(i) State how the resistance of the thermistor varies with temperature ?

……………………………………………………………… [1 mark] (b) An electrical component is connected to the output transistor so that the lamp is light up. Name the electrical component and state the functions.

………………………………………………………………… [1 mark] (ii) What is the resistance of the thermistor at 30 oC . Show on the graph how you determine the value of resistance.

…………………………………………………………………

…………..…………………………………………………………. [2 mark] (b) A thermistor and a light dependence resistance (LDR) are used to make a simple switch which control an air conditioner in a room as shown in Diagram 7.2.

[2 marks]

8(a) Diagram 7.1 shows a resistance against temperature graph for a thermistor.

Diagram 7.2 The air-conditioner is only activated either on a sunny day or at a hot night Keys : Input P : during the day – logic “1” Input P: at night - logic “0” Input Q : when hot - logic “1” Input Q : when cold - logic “0” Relay switch : switch on when output logic is “1” Relay switch : switch off when output logic “0” Table 7 shows a truth table operation indicates the logic gates which control the air-conditioner system. Input output P Q R 0 0 0 1 1 0 1 1 Table 7

Diagram 7.1

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(i) Using the keys given, complete the table 7 [1 mark] (ii) Name the logic gate in the circuit in Diagram 7. ………………………………………………………………… [1 mark] (iii) In the space below , draw a symbol of the logic gate in 7b(ii). [1 mark] (c) Diagram 7.3 shows a light dependent resistance, LDR , used in transistor circuit to control a road lamp labeled 240 V. 100 W.

Diagram 7.3 At night the road lamp is switched on automatically. (i) What is the function of resistor R1 ? …………………………………………………………………..[1mark] (ii) Explain how the circuit function at night. ……………………………………………………………………… ……………………………………………………………… [2 mark] (iii) Why the lamp is not connected directly to the transistor circuit? ……………………………………………………………… [1 mark]

(i)

9 (a) Diagram 6.1 shows a waveform on the screen of a cathode ray oscilloscope that is connected across R. Diagram 6.2 shows how an electric component Q is connected to the circuit.

Tick (√ ) the correct answer in the box provided. The inout power supply in diagram 6.1 is connected to Alternating current

(ii)

direct current

What is the function of component Q in diagram 6.2? …………………………………………………… [1mark] (iii) Draw the waveform produced on the screen in diagram 6.2 [2marks] (iv) Compare the waveform in diagram 6.1 and diagram 6.2. Name the process involved in diagram 6.2. …………………………………………………………………… ……………………………………………………………… [1mark] (b) Name the component Q in Diagram 6.2 …………………………………………………………………………… [1mark]

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(c) Component Q is made from a semiconductor material. One type of semiconductor is the n-type. Explain how the n-type semiconductor is produced. …………………………………………………………………………………… ……………………………………………………………… [2marks]

10.Diagram 4.1 shows the structure of a cathode ray oscilloscope (CRO).

[1mark] 11. Diagram 8.1 shows four electrical circuits with identical electrical components. The electrical circuits consist of a transistor , a bulb, a light dependent resistor, LDR, two resistors, R1 and R2 and battery as a power supply.

(a) State the process involved in producing electrons from electrode X. ………………………………………………………………[1mark] (b) Describe the type of motion of the electron moving from (i) Y to Z ………………………………………………………… [1mark] (ii) Z to the screen ………………………………………………………… [1 mark] (c) A student uses the CRO to study the output voltage from a bicycle dynamo. Diagram 4.2 shows the trace on the screen and the settings of the CRO. (i) State the type of current produced by the dynamo. ……………………………………………………….[1mark] (ii) Determine the frequency of the output voltage of the dynamo.

(iii)

(a) What is meant by power? ……………………………………………………………….[1 mark] (b) Based on Diagram 8.1, state the suitable characteristic of the arrangement position of the electrical components of the circuit to use as an automatic switch.

[2 marks] Sketch the new trace in Diagram 4.3 if the time-base setting is now set at 0.01 s/div.

(i) Resistor, R2 ....................................................................................

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Reason …………………………………………………………[2 marks] (ii) Resistor R1 and light dependent resistor, LDR ................................................................................ Reason ………………………………………………….[2 marks] (iii) Collector terminal of the transistor to the battery …………………………………………………. Reason …………………………………………………[2 marks] (c) Based on the answers in 8(b), state one suitable circuit in Diagram 8 to be use as an automatic switch. . …………………………………………………. [ 1 mark] (d) The circuit in 8(c) is used as an automatic switch. State the application of the circuit. ........................................................................... [ 1 mark] (e) Diagram 8.2 show a circuit transistor used as an amplifier. The transistor is on when the voltage across Y and Z is 1 V.

(a) (i) Name component Q …………………………………………………………………………….[1 mark] (ii) State two functions of component Q? …………………………………………………………….……………… [2marks] (b) What is the function of resistor R? …………………………………….………………………………………[1 mark] (c) (i) What happens to potential difference Vp at night? Explain. ………………………………………………………………………..[2 marks] (ii) Explain why the bulb is lighted up at night? …………………………………….…………………………………..

Diagram 8.2 When the potential difference accross Yand Z is 1 V; (i) What is the potential difference between X and Y? [ 1 mark]

…………………………………………………….…………………..[2 marks] (d) Bulb M is labeled 240 V, 60 W starts to light up when Vp is 2.0 V and the resistance of resistor P is 10 kΩ. Determine the maximum resistance of resistor S. [2 marks]

(ii) Calculate the maximum resistance of the rheostat for the transistor to switch on? [2 marks] 12. Diagram 8 shows a transistor circuit. The circuit is used to automatically switch on the bulb at night.

(e) What happens to the bulb when it is connected directly to the transistor circuit without using the relay switch. Explain why? …………………………………………………………………………………..

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…………………………………………………………………………[2 marks] 13. Diagram 6.1 and Diagram 6.2 shows two diodes A and B , two bulbs P and Q are connected to a dry cell with two different arrangement.

Diagram 6.1 Diagram 6.2 (a) Based on Diagram 6.1 and Diagram 6.2, (i) compare the connection of diodes to the terminal of the dry cell. …………………………………………………………………………..[1 mark] (ii) compare the lighting of the bulbs. …………………………………………………………………………..[1 mark] (iii) Relate the connection of diodes to the terminal of the dry cell with the lighting of the bulbs. …………………………………………………………………………..[1 mark] (b) (i) Draw the arrangement of four diodes and suitable power supply in the space given in Diagram 6.3 that can be used to produce full wave rectifier circuit.

[3 marks] (ii) Draw the wave form of full wave rectification [1 mark] (iii) Name an electronic component that can be used to smoothen the current produced. ………………………………………………………………………….[1 mark]

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