Electronics Question

8/14/2019 Electronics Question

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4 The diagram shows a logic gates circuit.

hich of the following truth tables output % in the circuit!

" & % " & %

A ' ' ( C ' ' '' ( ' ' ( (( ' ( ( ' '( ( ' ( ( (

" & % " & %

B ' ' ' D ' ' '' ( ( ' ( (( ' ' ( ' (

Objective 2004

1 The diagram shows the combination of three logic gates.

The truth table for the combination of the three logic gates is as follows.

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3 The circuit represents a oolean algebraic principle with output Z.

hich of the oolean algebraic expression represents the output Z!

A Z = X YB Z / X YC Z = X YD Z / X Y

4 hich of the following pairs of atoms can act as an impurity to produce an n0type semiconductor when doped into a pure semiconductor!A oron and phosphorusB )rsenic and antimonyC -ndium and galliumD )ntimony and gallium

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Objective 200

1 The diagram shows a circuit consisting of a diode and a bulb. hen the

switch is on, the bulb does not light up.

hat needs to be done to light up the bulb!

A %eplace with a new bulbB -ncrease the number of dry cellsC %everse the diode connectionD $onnect a resistor parallel to the bulb

2 The diagram shows a logic gate circuit with input signals, 1 and 2.

hich of the following output signals is produced by the logic gate circuit!

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Objective !200"#

1 hich of the following circuits can function!

2 hich of the following diagrams is an n0type semiconductor!

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3 The adding of impurity into pure semiconductor material is known as

) doping rectification$ amplification+ thermionic emission

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4 +iagram shows a combination of three logic gates.

Objective !200$#

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1. +iagram 56 show a transformer connected to a cathode ray oscilloscope.

Which of the following wave traces is correct when the extra coil is on the core and

connected in series with the secondary coil ?

2. iagra! 27 shows a circ"it connected to the cathode ray oscillosco#e $%&'(.

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Which of the following traces is the correct one shown on the %&' ?

7. hat is the function of a diode !

). )cts as a current amplifier )cts as an automatic switch$ 8tores electric charge+ )llows the current to pass in one direction only

9. +iagram 5: shows an automatics switch circuit to light up a bulb at night.

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hat changes should be done to light up the bulb during the day time !

). %everse the terminals of the battery. -nterchange %(and %5$. %eplace the npn transistor with a pnp transistor+. %eplace resistor %7with a resistor of lower resistance

6. +iagram 5; shows a logic gate circuit.

hich of the following truth tables represents output % in the circuit !

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P%&e' 2!2003#

Secti() A

( mark?

3ii4 $omplete the circuit in (mark?

3iii4 @ive one reason why 2#+ emmits light in a bright surroundings.

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>( mark?

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3b4 hat modification is reAuired to the circuit so that the 2#+ will emmits lightwhen the surroundings become dark!

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>( mark?

3c4 )n alarm is needed which emmits sound when there is a fire. Twomodifications have to be made to the circuit in 3a43ii4 by replacing electroniccomponents.

3i4 8tate one electronic component which needs to be replaced. @ive areason for your answer.

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>5 marks?

3ii4 *ame two electronic components that are needed to replace theunsuitable components.

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>5 marks?

3iii4 -n the space below, draw a circuit diagram to show the new circuit.

>5 marks?

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Secti() A !2004#

)li wishes to design a security system in his house as shown in


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3a4 -f the potential difference across resistor is 5 C, what is the potentialdifference across the infrared sensor!

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3b4 $omponent X has a high resistance when the surroundings are dark and alow resistance in bright surroundings.*ame the component X.

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3c4 $omponent 8 is a switch that connects the 59' C ax spotlight circuit.3i4 hat type of switch is component 8!

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3ii4 hy is component 8 necessary in the circuit!

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3d4 The following truth table shows the operation of a logic gate in the circuit in


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+etectors 8(and 85will give input ' to logic gate system when they receive a lowlevel of radiation.

+etectors 8(and 85will give input ( to the logic gate system when they receive ahigh level of radiation.

3a4 8tate the level of the pesticide in the bottle if the input 8(is '.@ive a reason for your answer.

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>5 marks?

3b4 8tate the level of the pesticide in the bottle if the input 8( is (.@ive the reason for your answer.

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>5 marks?


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3c4 *ame the logic gate I.

===================================================================>( mark?

3d4 $omplete the truth tables for " and &.

3e4 hen the output of the logic gate system is (, it indicates the volume of thepesticide in the bottle is within the acceptable range.

hen the ouput of the logic gate system is ', it indicates the volume of thepesticide in the botte is outside the acceptable range.

3i4 ased on the output of the truth tables in 3d4, which combination oflogic gates is suitable to be used for the logic gate system!

$ombination of logic gate ======================= >( mark?

3ii4 @ive two reasons for your choice.

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5. ===================================================

===================================================>5 marks?

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Secti() A !200"#

) student wants to build a simple lift motor control system which operates using twobuttons, ) and , for a two0storey building. )D Hp button D +own button The liftmotor only activates when someone presses any one of the buttons. +iagram B.(

shows the circuit that can be used to activate the motor.

1eysD

uttons ) and D hen pressed, logic J(K

*ot pressed, logic L'L

X utput D Iotor is activated, logic J(K

3a4 Table B is a truth table which shows the operations of the logic gates in a liftmotor control system.

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3i4 Hsing the keys given, complete Table B. >5 marks?

3ii4 *ame the logic gate in the circuit in +iagram B.(.

==============================================================>( mark?

3iii4 -n the space below, draw the logic gate symbol in B3a43ii4.

>(mark?

3b4 hy is a relay switch needed in the circuit!

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>(mark?

3c4 The door of the lift is fitted with a light transmitter and a detector which is alight dependent resistor.

-f the light dependent resistor detects light, the relay switch is activated and

the lift door will close.

+iagram B.5 shows an electronic circuit for the control system of the lift door.

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3i4 8tate the relationship between the resistance and the intensity of lightreceived by the light dependent resistor.

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>(mark?

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3ii4 $omplete the circuit in +iagram B.5 by drawing the resistor and the lightdependent resistor using the symbols given below.

3iii4 #xplain how the circuit functions.

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>(mark?

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Secti() B !200$#

+iagram ('.( and +iagram ('.5 show two electrical circuits containingsemiconductor diodes.

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3a4 hat is meant by a semiconductor ! >( mark?

3b4 Hsing diagram ('.( and +iagram ('.5, relate the lighting of the bulbs, thecurrent and the way the diode is connected to the terminals of the battery todeduce a relevant physics concept.

>6 mark?3c4 +iagram ('.7 shows a full wave rectifier circuit.

3i4 +raw the wave form of a full wave rectification. >( mark?

3ii4 ) capacitor is placed across the output to smooth the current.+raw the wave form produced.#xplain how a capacitors is used to smooth the current. >7 mark?

3d4 +iagram ('.9 shows a circuit a transistor that acts as an automatic switch.

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The transistor in the circuit causes the light emitting diode 32#+4 to light upwhen it is dark.) technician wants a fan labeled 59'C, ('' in a room to be automaticallyswitched on when the room is hot..

8uggest modifications that can be made to the circuit in +iagram ('.9 so thatthe fan can be automatically switched on when the room is hot.+raw the modified circuit.

8tate and explain the modifications based on the following aspects D

0 the electrical components that are needed to replace the 2#+ and thelight dependent resistor 32+%4 in the circuit.

0 the positions of the electrical components in the circuit.>(' mark?

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