Physics Electronics MCQs Chapter 7 Class 12 - PLS Academy

Physics Electronics MCQs Chapter 7 Class 12

Physics Electronics is a vital chapter of Class 12 Physics and plays an important role in free preparations for entry tests and FSC Part-II exams. It is commonly included in MDCAT, NUMS, AKU, NUST, UET ECAT, and FSC board examinations. This chapter covers key topics such as semiconductors, diodes, transistors, logic gates, and amplifiers. Many students use entry test MCQs and practice tests to strengthen their understanding and problem-solving skills.

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Created on February 07, 2022 By Ali Durrani

Physics Ch 18 Class 12 Electronics

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1 / 58

If peak voltage across a full wave rectifier is 20V then Vrms is:

PMC Practice 10
Physics
Electronics
Elimination Tool:

A) 7.07v

B) 14.14v

C) 16.8v

D) 12v

2 / 58

If the temperature of diode increases the leakage current will

PMC Sample 2
Physics
Electronics
Elimination Tool:

A) increases

B) decreases

C) remains same

D) none of them

3 / 58

Transistors can be used as:

PMC Practice 10
Physics
Electronics
Elimination Tool:

A) Half wave rectifier

B) Full wave rectifier

C) Both

D) None of these

4 / 58

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

PMC Sample 2
Physics
Electronics
Elimination Tool:

A) 100 Hz

B) 25Hz

C) 50Hz

D) 200Hz

5 / 58

Which of the following is not a type of rectifier?

PMC Practice 12
Physics
Electronics
Elimination Tool:

A) Phase wave rectifier

B) Full wave

C) halfwave

D) none of them

6 / 58

In photodiodes, the bias voltage is applied in ______ bias form.

NTS 2016 DUHS & JSMU
Physics
Electronics
Elimination Tool:

A) Forward

B) Resistance

C) Reverse

D) Converse

7 / 58

A cable 4 km long and of total resistance 1 Ohm carries electric current from a generator producing 100kW at 10,000 Volts. The current in amperes in the cable is:

PMC Practice 5
Physics
Electronics
Elimination Tool:

A) 10

B) 10,000

C) 1000

D) 100,000

8 / 58

When reverse bias of a p-n junction diode is increased, a stage comes when electric field set up is sufficient to rupture covalent bonds and release a large number of holes and electrons. This breakdown phenomenon is known as:

NUMS 2018
Physics
Electronics
Elimination Tool:

A) Avalanche breakdown

B) Zoner breakdown

C) Early effect

D) High – field emission

9 / 58

A logic gate has four inputs. Its possible input combinations will be:

NUMS 2015
Physics
Electronics
Elimination Tool:

A) 4

B) 16

C) 32

D) 64

10 / 58

A full wave rectifier uses load resistor of 1500 Ω. Assume the diodes have Rf= 10 Ω, Rr= ∞. The voltage applied to diode is 30V with a frequency of S0Hz. Calculate the AC power input.

PMC Practice 14
Physics
Electronics
Elimination Tool:

A) 358.98mW.

B) 275.2mW.

C) 145.76 mW.

D) 456.78 mW.

11 / 58

A semiconductor photodiode is a:

NTS 2011
Physics
Electronics
Elimination Tool:

A) reverse biased junction diode

B) forward biased junction diode

C) half wave rectifier

D) full wave rectifier

12 / 58

Input resistance of an Operational Amplifier is:

NUMS 2019 Reconduct
Physics
Electronics
Elimination Tool:

A) Very low

B) Very high

C) Moderate

D) Becomes infinite

13 / 58

A type of metals containing alloys, ceramics etc., when heated their temperature reaches to a state called Transition temperature state and their resistance reaches to zero. These types of metals are called:

Conductors

Insulators

Semi-conductors

Superconductors

14 / 58

The electron volt is the unit of __________.

PMC Practice 3
Physics
Electronics
Elimination Tool:

A) Electric current

B) Electric potential

C) Electric energy

D) Electric flux

15 / 58

Operational amplifier with an LDR is used as a:

NUMS 2019 Reconduct
Physics
Electronics
Elimination Tool:

A) Half wave rectifier

B) Gate

C) Night switch

D) Full wave rectifier

16 / 58

AC is converted to D.C by:

Oscillator

Rectifier

Amplifier

DC motor

17 / 58

A transistor cannot be used as

As a Switch

As an Amplifier

As a Power Source

As an inverter

18 / 58

A negligible small current between input terminals of the operational amplifier is because of:

UHS 2019
Physics
Electronics
Elimination Tool:

A) High output resistance

B) Low output resistance

C) High input resistance

D) Low input resistance

19 / 58

Full wave rectifier uses:

PMC Practice 5
Physics
Electronics
Elimination Tool:

A) One diode

B) Two diodes

C) Three diodes

D) Four diodes

20 / 58

In a centre tap full wave rectifier if Vm is the peak voltage across the secondary of transformer, the maximum voltage across reverse bias is

PMC Practice 11
Physics
Electronics
Elimination Tool:

A) Vm

B) Vm/v2

C) 2Vm

D) Vm/3

21 / 58

The principle behind the working of cathode ray oscilloscope is:

PMC Sample 1
Physics
Electronics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Oscillation

B) Half wave rectification

C) Full wave rectification

D) None of these

22 / 58

Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100 V. Let the load resistance R = 10 kΩ. Calculate the fraction of the cycle during which the diode is conducting:

PMC Practice 13
Physics
Electronics
Elimination Tool:

A) 1.06 %

B) 2.06 %

C) 3.18 %

D) 4.82 %

23 / 58

Non-inverting amplifier circuits have?

PMC Practice 2
Physics
Electronics
Elimination Tool:

A) A very high input impedance

B) A very low input impedance

C) A low output impedance

D) None of the above options is correct

24 / 58

Which of the following rectifier uses a wheatstone bridge to rectify signals?

PMC Practice 13
Physics
Electronics
Elimination Tool:

A) Half wave

B) Full wave

C) Bridge

D) All of the above options are correct

25 / 58

To get a peak load voltage of 40V out of a bridge rectifier, what should be the approximate rms value of secondary voltage?

PMC Practice 5
Physics
Electronics
Elimination Tool:

A) 0 V

B) 14.4 V

C) 28.3 V

D) 56.6 V

26 / 58

A diode works in ___ bias for rectification.

PMC Practice 11
Physics
Electronics
Elimination Tool:

A) Forward

B) Reverse

C) Mid

D) Positive

27 / 58

At least how many diodes are required to covert A.0 fully into D.C?

28 / 58

The process of converting alternating current to direct current is called?

PMC Practice 14
Physics
Electronics
Elimination Tool:

A) Modulation.

B) Amplification.

C) Oscillation.

D) Rectification.

29 / 58

In half wave rectification, the output DC voltage is obtained across the load for?

PMC Practice 10
Physics
Electronics
Elimination Tool:

A) The positive half cycle of input AC

B) The negative half cycle of input AC

C) The positive and negative half cycles of input AC

D) Either positive or negative half cycle of input AC

30 / 58

In half-wave rectification, the output DC voltage is obtained across the load for ______.

PMC Practice 9
Physics
Electronics
Elimination Tool:

A) The positive half cycle of input AC

B) The negative half cycle of input AC

C) The positive and negative half cycles of input AC

D) Either positive or negative half cycle of input

31 / 58

When transistor Is forward biased then resistance will be: b a) Nano ohms ) Kilo ohms c) Mega ohms

Nano ohms

Kilo ohms

Mega ohms

Milli ohms

32 / 58

Which of the following is a type of rectifier?

PMC Practice 15
Physics
Electronics
Elimination Tool:

A) Half wave

B) Full wave

C) Bridge

D) All of the above options are correct

33 / 58

When an Operational amplifier is used as Inverting amplifier, then angle between its output and input signal is:

NUMS 2019 Cancelled
Physics
Electronics
Elimination Tool:

B) 45 degrees

C) 60 degrees

D) 90 degrees

E) 180 degrees

34 / 58

Maximum efficiency of half wave rectifier is:

PMC Practice 11
Physics
Electronics
Elimination Tool:

A) 80.6 %

B) 40.6 %

C) 70%

D) 50%

35 / 58

In the breakdown region zener behaves like a

PMC Sample 2
Physics
Electronics
Elimination Tool:

A) Constant current

B) Constant voltage

C) constant resistance

D) none of them

36 / 58

If x and y are the input of the GATE, and z is the output, the following table represents:

37 / 58

When semi-conductors dopped In
then they are p-type

Pentavalent

Trivalent

Both a and b

None of these

38 / 58

The basic purpose of filter is to?

PMC Practice 1
Physics
Electronics
Elimination Tool:

A) Minimize variation in ac signal

B) Suppress hannonics in rectified output

C) Remove ripples from the rectified output

D) Stabilize dc output voltage

39 / 58

The number of diodes in centre-tapped full-wave rectifier is:

PMC 2021 Tested
Physics
Electronics
Elimination Tool:

A) 2

B) 3

C) 4

D) 1

40 / 58

Which option in the following best explains Base of a transistor?

NUMS 2017
Physics
Electronics
Elimination Tool:

A) Base has no impurity

B) Base has less concentration of impurity as compared to emitter and collector

C) Base has more concentration of impurity as compared to emitter

D) Base has more concentration of impurity as compared to collector

41 / 58

Which two or more of the following actions would increase the energy stored in a parallel plate capacitor when a constant potential difference is applied across the plates:

PMC Practice 5
Physics
Electronics
Elimination Tool:

A) Decreasing the area of the plates & decreasing the separation between the plates

B) Decreasing the area of the plates & increasing the separation between the plates & inserting a dielectric between the plates

C) Increasing the area of the plates & decreasing the separation between the plates & inserting a dielectric between the plates

D) Increasing the area of the plates & increasing the separation between the plates

42 / 58

In full wave rectifier with input frequency 50 Hz, the ripple in the output is mainly of frequency?

PMC Practice 10
Physics
Electronics
Elimination Tool:

A) 25 Hz

B) 50 Hz

C) 100 Hz

D) Zero

43 / 58

If both inputs “A” and “B” are ON and the output is also ON. This type of gate is known as:

NUMS 2017
Physics
Electronics
Elimination Tool:

A) OR Gate

B) AND Gate

C) NAND Gate

D) NOR Gate

44 / 58

In full wave rectifier with input frequency 50 Hz the ripple in the output is mainly of frequency

PMC Practice 6
Physics
Electronics
Elimination Tool:

A) 25 Hz

B) 50Hz

C) 100 Hz

D) Zero

45 / 58

Gamma rays are attracted towards

PMC Practice 11
Physics
Electronics
Elimination Tool:

A) Negative plate

B) Positive plate

C) No deflection

D) Pass through the medium

46 / 58

Majority charge carriers in P-type semiconductor are

PMC Sample 2
Physics
Electronics
Elimination Tool:

A) Holes

B) electrons

C) neutrons

D) protons

47 / 58

A signal of -80 mV is applied to the inverting terminal of the amplifier while the non inverting terminal is grounded. The gain of the amplifier is 25 using Rin(R1) equal to 3 ohms and Rf(R2) equal to 75 Ohms. What would be the value of the output signal?

UHS 2018
Physics
Electronics
Elimination Tool:

A) 200 mV

B) -3 V

C) 2 V

D) 3 V

48 / 58

The half wave rectifier has how many diodes?

PMC 2021 Tested
Physics
Electronics
Elimination Tool:

A) 4

B) 1

C) 3

D) 2

49 / 58

If the input frequency of a full-wave rectifier is 50 Hz, its ripple frequency is:

PMC 2021 Tested
Physics
Electronics
Elimination Tool:

A) 25 Hz

B) None of these

C) 50 Hz

D) 100 Hz

50 / 58

The open-circuit test in a transformer is used to measure?

PMC Practice 3
Physics
Electronics
Elimination Tool:

A) Copper loss

B) Winding loss

C) Total loss

D) Core loss

51 / 58

A half-wave rectifier uses:

PMC Practice 13
Physics
Electronics
Elimination Tool:

A) One diode

B) Two diodes

C) Three diodes

D) Four diodes

52 / 58

A capacitor and an inductor are connected to A.C. supply. If we double the frequency of A.C. supply then the effect on reactance of capacitor XC and reactance of inductor XL will be:

NUMS 2019 Cancelled
Physics
Electronics
Elimination Tool:

A) Both XC and XL are doubled

B) Both XC and XL are halved

C) XC is doubled and XL reduces to half

D) XL is doubled and XC reduces to half

53 / 58

Half wave voltage multiplier can provide any degree of voltage multiplication by cascading diodes and capacitors.

PMC Practice 12
Physics
Electronics
Elimination Tool:

A) any doubler

B) any tripler

C) any multiplication

D) none of them

54 / 58

______ is equivalent to AND Gate followed by a NOT Gate.

NUMS 2017
Physics
Electronics
Elimination Tool:

A) NOR Gate

B) NAND Gate

C) NOT Gate

D) None of these

55 / 58

The width of depletion region Increases due to:

Transistor

Minority charge carriers

Majority charge carriers

None of these

56 / 58

Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100V. Let the load resistance R = 10kΩ . Calculate the fraction of the cycle during which the diode is conducting:

PMC Practice 5
Physics
Electronics
Elimination Tool:

A) 1.06 %

B) 2.06 %

C) 3.18 %

D) 4.82 %

57 / 58

The ripple factor of half-wave rectifier is?

PMC Practice 14
Physics
Electronics
Elimination Tool:

A) 1.21.

B) 0.8.

C) 0.6.

D) 0.4.

58 / 58

In a npn transistor, the current IEthat flows in the emitter circuit is:

NTS 2016 DUHS & JSMU
Physics
Electronics
Elimination Tool:

A) IC+ IB

B) IC- IB

C) ICx IB

D) Zero

Your score is

The average score is 55%

Importance of Electronics MCQs

Electronics helps students understand current flow in semiconductors and the working of electronic devices. Moreover, exams frequently include MCQs based on diode circuits, transistor characteristics, and digital logic applications. Practicing topic-wise MCQs and short tests improves speed, accuracy, and confidence. Therefore, consistent practice is essential for excelling in competitive exams.

Effective Strategy for Free Preparations

Students should revise formulas, understand device behavior, and solve chapter-wise MCQs regularly. In addition, attempting free tests and past questions helps identify frequently repeated patterns. PLS Academy provides structured resources that support free entry test preparations for Physics Electronics and other Class 12 Physics chapters.

JazakAllah.

Comments

One response to “Physics Electronics MCQs Chapter 7 Class 12”

Abeeha

March 18, 2023

A signal of -80 mV is applied to the inverting terminal of the amplifier while the non inverting terminal is grounded. The gain of the amplifier is 25 using Rin(R1) equal to 3 ohms and Rf(R2) equal to 75 Ohms. What would be the value of the output?????
Explain plz