Physics Alternating Current MCQs Chapter 5 Class 12

Created on February 07, 2022 By Ali Durrani

Physics Ch 16 Class 12 Alternating Current

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1 / 73

In a step-down transformer, the current in the primary coil is ______ than that in the secondary coil.

PMC 2021 Tested
Physics
Alternating Current
Elimination Tool:

A) None of these

B) More

C) Equal

D) Less

2 / 73

The maximum efficiency of a half-wave rectifier is:

PMC Practice 3
Physics
Alternating Current
Elimination Tool:

A) 80.6 %

B) 40.6 %

C) 70 %

D) 50 %

3 / 73

In a pure resistive circuit current and voltage are

In phase

Out of phase

Current leads

Voltage leads

4 / 73

The ripple factor of a half-wave rectifier is:

PMC Practice 2
Physics
Alternating Current
Elimination Tool:

A) 1.21

B) 0.8

C) 0.6

D) 0.4

5 / 73

A circuit that adds positive or negative D.C. voltage to an input sine wave is called:

PMC Practice 4
Physics
Alternating Current
Elimination Tool:

A) Clamper

B) Clipper

C) Diode clamp

D) Limiter

6 / 73

Consider two capacitors with capacitance 2µF and 4µF. With which type of connection will the 4µF capacitor have a greater amount of stored energy than the 2µF capacitor?

PMC Practice 2
Physics
Alternating Current
Elimination Tool:

A) Series

B) Parallel

C) Either series or parallel

D) Neither series nor parallel

7 / 73

A half wave rectifier is operating from 50 Hz mains, fundamental frequency of ripple will be

PMC Sample 3
Physics
Alternating Current
Elimination Tool:

A) 100 Hz

B) 25 Hz

C) 200Hz

D) 50Hz

8 / 73

Which of the following color has the highest energy?

Blue

Green

Violet

Yellow

9 / 73

The angle made by the coil of an AC generator at a time Interval 3T/4 is?

2ℼ

2/ℼ

3ℼ/2

ℼ

10 / 73

The number of diodes in bridge rectifier is

PMC Sample 3
Physics
Alternating Current
Elimination Tool:

A) 4

B) 3

C) 2

D) 5

11 / 73

Alternating Current Generators use:

PMC Practice 5
Physics
Alternating Current
Elimination Tool:

A) Coiled rings

B) Split rings

C) Slip rings

D) Solenoid rings

12 / 73

A full wave rectifier is operating from 50 Hz mains. Fundamental frequency of ripple will be:

PMC Practice 1
Physics
Alternating Current
Elimination Tool:

A) 100 Hz

B) 25 Hz

C) 50 Hz

D) 200 Hz

13 / 73

If a half wave rectifier is used to convert 50Hz AC into DC, then the number of pulses present in rectified voltage is:

PMC Sample 1
Physics
Alternating Current
Elimination Tool:

A) 25

B) 50

C) 100

D) 75

14 / 73

In electronic circuits, a PN junction diode is used to convert alternating current into direct current. This process is called:

NTS 2018
Physics
Alternating Current
Elimination Tool:

A) Rectification

B) Amplification

C) Doping

D) Integrated Circuit

15 / 73

If the instantaneous current in a circuit is given by I = A sin (wt) ampere, the RMS value of the current is:

PMC Practice 3
Physics
Alternating Current
Elimination Tool:

A) 2A

B) A/√2

C) 2√2A

D) Zero

16 / 73

Power factor of the pure capacitive circuit is?

-1

0

+1

0.5

17 / 73

The process of combining low frequency waves with high frequency is called:

Rectification

Amplification

Modulation

Magnification

18 / 73

PIV stands for :

PMC 2020
Physics
Alternating Current
Elimination Tool:

A) Positive inverse voltage

B) Pawn Bh Integrated voltage

C) Peak inverse voltage

D) Peak integrated voltage

19 / 73

P = Irms Vrms Is applicable for

AC only

DC only

Both a and b

None of these

20 / 73

The maximum instantaneous value measured from zero value is known as?

PMC Sample 3
Physics
Alternating Current
Elimination Tool:

A) peak value

B) peak to peak value

C) cycle

D) period

21 / 73

Voltage after which in forward bias current start to rise with increase in voltage is called:

PMC Sample 3
Physics
Alternating Current
Elimination Tool:

A) Breakdown voltage

B) Reverse voltage

C) Forward voltage

D) Knee voltage

22 / 73

If the peak voltage is 9V, calculate the peak to peak voltage.

PMC Practice 8
Physics
Alternating Current
Elimination Tool:

A) 9V

B) 18V

C) 4.5V

D) 0V

23 / 73

Which of the following are component of half wave rectifier?

PMC Practice 1
Physics
Alternating Current
Elimination Tool:

A) Transformer

B) Load resistance

C) Power supply

D) All of the above

24 / 73

An alternation voltage V (in volts) is represented by the equation:
V = 300 sin (100πt)
What is the value of “f” for this voltage?

UHS 2019
Physics
Alternating Current
Elimination Tool:

A) 100 Hz

B) 50 Hz

C) 25 H

D) 200 Hz

25 / 73

What is the instantaneous power dissipated through a resistor of resistance 10 ohm if it is connected to an AC source of frequency 15 Hz at 1/180 sec if peak value is 20 V?

UHS 2018
Physics
Alternating Current
Elimination Tool:

A) 10 W

B) 100 W

C) 40 W

D) Cannot be determined

26 / 73

If a half-wave rectifier is used to convert 50 Hz AC into DC, then the number of pulses present in the rectifier voltage is:

PMC Practice 2
Physics
Alternating Current
Elimination Tool:

A) 25

B) 50

C) 100

D) 75

27 / 73

In a half wave rectifier, the diode conducts during:

NUMS 2019 Reconduct
Physics
Alternating Current
Elimination Tool:

A) One half of the input cycle

B) A portion of the positive half of the input cycle

C) A portion of the negative half of the input cycle

D) Both halves of the input cycles

28 / 73

Transformer is used in rectification to ___________ the supply voltage.

PMC Practice 5
Physics
Alternating Current
Elimination Tool:

A) Step up

B) Step down

C) Equalize

D) None of these options is correct

29 / 73

Electromagnetic waves are produced due to flow of

Negative charge

Positive charge

Both a and b

None of these

30 / 73

The frequency of applied AC is 2 kHz. Its time period will be:

PMC Practice 3
Physics
Alternating Current
Elimination Tool:

A) 0.5 x 10-3 sec

B) 0.5 second

C) 5 sec

D) 2 sec

31 / 73

Impedance in RLC series circuit Is given by

a

b

c

d

32 / 73

The bridge rectifier is preferred to an ordinary two diode full-wave rectifier because?

PMC Practice 2
Physics
Alternating Current
Elimination Tool:

A) It needs a much smaller transformer for the same output

B) No center tap required

C) Less PIV rating per diode

D) All of the above options are correct

33 / 73

Resistance of RCL series circuit at resonance Is?

Xc

R

Xi

Xi R Xc

34 / 73

The principle of a capacitor is based on which of the following facts?

NTS 2011
Physics
Alternating Current
Elimination Tool:

A) potential of a conductor is greatly increased with a decrease in the charge in it increase in the charge in it. affecting the charge in it

B) potential of a conductor is greatly reduced with an increase in the charge in it.

C) potential of a conductor is greatly increased without affecting the charge in it

D) potential of a conductor is greatly reduced without affecting the charge in it

35 / 73

Power factor in an AC circuit Is?

cos theta

sin theta

tan theta

None of these

36 / 73

An Inductor of 1H Is connected across a 220V, 50Hz supply. The peak value of current is approximately:

0.5A

0.7A

1A

1.4A

37 / 73

The rectifier is a device which converts?

PMC Practice 3
Physics
Alternating Current
Elimination Tool:

A) AC to DC

B) DC to AC

C) AC to triangular current

D) DC to triangular current

38 / 73

Half wave voltage multipliers can provide what degree of voltage multiplication?

PMC Practice 4
Physics
Alternating Current
Elimination Tool:

A) Any doubler

B) Any tripler

C) Any multiplication

D) None of them

39 / 73

Mutual inductance has a practical role in performance of:

PMC Practice 4
Physics
Alternating Current
Elimination Tool:

A) AC generator

B) Radio choke

C) DC generator

D) Transformer

40 / 73

Impedance of a circuit Is calculated as:

Vrms/Irms

Irms/Vrms

IrmsVrms

Vrms/R

41 / 73

What is the range of typical band gap in conductors

PMC Sample 3
Physics
Alternating Current
Elimination Tool:

A) 100-1000eV

B) 0.5-10eV

C) 0.01-0.1 eV

D) 10000-10000000eV

42 / 73

Wavelength of X-rays is of the order of?

Centimeter

Micron

Angstrom (10^-6 m)

Meter

43 / 73

In RLC series circuit at resonance, the A.C voltage across Resistance R, Inductance L and capacitance C are 5V, 10V and 10 V respectively. The A.C voltage applied to the circuit will be:

NUMS 2015
Physics
Alternating Current
Elimination Tool:

A) 20 V

B) 10 V

C) 5 V

D) 25 V

44 / 73

Identify the factor on which mutual inductance does not depend:

PMC Practice 3
Physics
Alternating Current
Elimination Tool:

A) Relative orientation

B) Relative separation of two coils

C) Reciprocity

D) Permeability of the core material

45 / 73

If an AC voltage of rms value of 10 volts is applied as input of a half-wave rectifier, then the voltage value of the DC output will be:

PMC Practice 4
Physics
Alternating Current
Elimination Tool:

A) 10 V

B) 10.3 V

C) 10.7 V

D) 9.3 V

46 / 73

Power factor. of RLC circuit at Resonance Is

0

1

-1

0.5

47 / 73

The frequency of AC used in Pakistan is

30c/s

50 c/s

90c/s

180c/s

48 / 73

The output voltage of a rectifier is:

PMC Practice 4
Physics
Alternating Current
Elimination Tool:

A) Smooth

B) Pulsating

C) Perfectly direct

D) Alternating

49 / 73

In which rectifier is the ripple factor less?

PMC Practice 1
Physics
Alternating Current
Elimination Tool:

A) Full wave

B) Half wave

C) Both A and B

D) None of them

50 / 73

Step up transformer have ________ turns in secondary coil.

PMC Practice 1
Physics
Alternating Current
Elimination Tool:

A) More

B) Less

C) Equal

D) Zero

51 / 73

that the supply for the potentiometer is taken?

PMC Practice 8
Physics
Alternating Current
Elimination Tool:

A) From a source which is not the same as the unknown voltage

B) From a battery

C) From the same source as the unknown voltage

D) Any of the above

52 / 73

For an ideal step-up transformer Ps ——- Pp.

PMC Practice 8
Physics
Alternating Current
Elimination Tool:

A) Equal to

B) Greater than

C) Less than

D) None of these

53 / 73

In case of half wave rectification the resistance of diode during negative half of A.C is:

UHS 2018
Physics
Alternating Current
Elimination Tool:

A) Very high

B) Very low

C) A few ohms

D) Negative

54 / 73

In a step up transformer ________.

NTS 2019
Physics
Alternating Current
Elimination Tool:

A) Vs > Vp while Is > Ip

B) Vs Ip

C) Vs = Vp while Is > Ip

D) Vs > Vp while Is < Ip

55 / 73

Current that fluctuates periodically with time is ——

PMC Practice 4
Physics
Alternating Current
Elimination Tool:

A) DC current

B) BC current

C) ACcurrent

D) Magnetic current

56 / 73

In a practical transformer mutual induction between primary and secondary coils takes place. In such transformer what can be deduced about the power.

UHS 2018
Physics
Alternating Current
Work, Power & Energy
Elimination Tool:

A) Power output = Power input

B) Power output > Power input

C) Power output ≥ Power input

D) Power output < Power input

57 / 73

The AC generator is similar to:

PMC 2021 Tested
Physics
Alternating Current
Elimination Tool:

A) Transformer

B) None of these

C) Inductor

D) Capacitor

58 / 73

Which of the following remains unchanged in a transformer.

PMC Sample 3
Physics
Alternating Current
Elimination Tool:

A) Voltage

B) Current

C) Power

D) Capacitance

59 / 73

Simple oscillating circuit consists of?

Inductor & Capacitor

Resistance & capacitor

Resistance & coil

Inductor and resistance

60 / 73

An alternating voltage source is connected to a resistor R, and a capacitor C, then which of the following statements about phase angle between voltage V and current I is correct?

NUMS 2019 Cancelled
Physics
Alternating Current
Elimination Tool:

A) In the resistor, I leads V by 90 degrees – In the capacitor, I leads V by 90 degrees

B) In the resistor, I lags V by 90 degrees – In the capacitor, I leads V by 90 degrees

C) In the resistor, I and V are in phase – In the capacitor, I leads V by 90 degrees

D) In the resistor, I and V are in phase – In the capacitor, I lags V by 90 degrees

61 / 73

The principle of an AC generator is.

NTS 2019
Physics
Alternating Current
Elimination Tool:

A) Lenz's law

B) Faraday's Law

C) Self-induction

D) Ampere's law

62 / 73

Reactance of an Inductor Is given by:

wL

1/wL

wC

1/wC

63 / 73

In a bridge type full-wave rectifier, if Vm is the peak voltage across the secondary coil of the transformer, the maximum voltage coming across each reverse biased diode is:

PMC Practice 5
Physics
Alternating Current
Elimination Tool:

A) Vm

B) Vm/√2

C) 2Vm

D) Vm3

64 / 73

The direction of current through the load resistance of a full-wave rectification circuit:

UHS 2019
Physics
Alternating Current
Elimination Tool:

A) remains constant

B) inverts for positive cycle

C) changes for every cycle

D) inverts for negative cycle

65 / 73

Voltage Is current In RC circuit.

Leading

Lagging

In Phase

None of these

66 / 73

Power of RCL circuit at resonance Is?

Zero

Minimum

Maximum

None of these

67 / 73

X-rays have frequency greater than

Visible light

Ultraviolet

Microwaves

All of these

68 / 73

A diode works in _______ bias for rectification.

PMC Practice 6
Physics
Alternating Current
Elimination Tool:

A) Forward

B) Reverse

C) Mid

D) Positive

69 / 73

The use of a capacitor filter in a rectifier circuit gives satisfactory performance only when the load:

PMC Practice 3
Physics
Alternating Current
Elimination Tool:

A) Current is high

B) Current is low

C) Voltage is high

D) Voltage is low

70 / 73

What will be the Impedance for V = 10 sin(wt) and I = 20 sln(wt)

200 ohm

2 ohm

0.5 ohm

0.707 ohm

71 / 73

At resonance, the RLC circuit behaves like:

Pure Inductive

Pure Resistive

Pure Capacitive

All of these

72 / 73

In a full-wave rectification, the number of diodes used are:

PMC 2020
Physics
Alternating Current
Elimination Tool:

A) 1

B) 2

C) 3

D) 4

73 / 73

RLC circuit can be excited by

AC

DC

Both a and b

None of these

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Physics Alternating Current MCQs Chapter 5 Class 12

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