Physics Electronics Online Mcqs Test

Malik TahirLast Updated: October 13, 2025

Important Electronics Question and Answer

Total Questions:	177
Time Allowed:	60 Minutes
Total Marks:	177
How to Attempt Test:	Please choose the right Option in MCQ-type question.
Test Helpful For:	Physics Test ECAT Test MDCAT Test FPSC/PPSC/SPSC/KPPSC/BPSC/AJKPSC/NTS Physics Interview Question Answer

Physics Electronics Practice Test Online With Explanation

Please wait...

1. When the conductivity of a semiconductor is only due, to breaking of covalent bonds, the semiconductor is called

Extrinsic

n-type

Intrinsic

p-type

2. The part of a transistor which is most heavily doped to produce large number of majority carriers is

Can be any of the above three

Emitter

Base

Collector

3. Young’s modulus for copper is

110 Nm¯²

91 x 10 Nm¯²

70 x 10 Nm¯²

None of these

4. In the p-type semi-conductor the majority and minority charge carriers are respectively

Holes and electrons

Electrons and holes

Electrons and protons

Protons and electrons

5. When a semiconductor is continuously heated, then value of its resistance

Remains unchanged

Decreases and then increases

Increases

Decreases

6. When no light is incident on photodiode, the reverse current is

Zero

Almost negligible

Very high

Very low

7. A diode as a rectifier converts:

Low voltage to high voltage

D.C. into A.C.

A.C. into D.C.

High voltage to low voltage

8. Non-inverting amplifier circuits have

None of these

A low output impedance

A very high input impedance

A very low input impedance

9. Which of the following is not characteristic of an op—amp

It offers a very high inputs resistance to the input current

It offers a very low open loop gain all of above

It offers a very low output resistance

None of these

10. In insulators

Valence band is partially filled with electrons

Conduction band is partially filled with electrons

Conduction band is empty and valence band is filled with electrons

Conduction band is filled with electrons and valence bad is empty

11. The logic gate that will have HIGH or “1” at its output when any one of its input if HIGH is a(n):

AND gate

NOT gate

NOR gate

OR gate

12. The materials in which valence band and conduction band overlap are called

Conductors

Semiconductors

Superconductors

Insulators

13. The part of a transistor which is heavily doped to produce large number of majority carriers is

Emitter

Any of the above depending on nature of transistor

Collector

Base

14. In forward bias, the width of potential barrier in a p-n junction diode

First A and B

Remains constant

Increases

Decreases

15. A diode as a rectifier converts:

A.C. into D.C.

D.C. into A.C.

Low voltage to high voltage

High voltage to low voltage

16. When we apply reverse bias to a junction diode, it

Increase the majority carrier current

Increase the minority carrier current

Raises the potential barrier

Lowers the potential barrier

17. The ratio β represents

18. The thickness of the base is equal to

Very small as compared to the thickness of emitter and collector

Thickness of emitter

Thickness of collector

Mean of thickness of emitter and collector

19. If p-type material of the PN-junction is connected with positive terminal of the battery and n-type material with negative terminal of the battery, it is said to be

Forward biased

None of these

Reversed biased

Zero biased

20. If on increasing temperature the resistance decreases, then it is

Semiconductor

Insulator

None of these

Superconductor

21. On increasing the reverse bias to a large value in a p-n junction diode current

Suddenly increases

Decreases slowly

Remain fixed

Increases slowly

22. Photodiode is used for

None of these

Detection of light

Light display

Emission of light

23. Output voltage in full wave rectification is not smooth. In order to have smooth output voltage

Capacitor is used

Solvent is used

None of these

Resistor is used

24. When Ge crystal is doped with phosphorus atom, then it becomes

n-type

Superconductor

p-type

Insulator

25. To obtain a p-type germanium semiconductor, it must be doped with

Arsenic

Phosphorus

Antimony

Indium

26. When n-p-n transistor is used as an amplifier,

Holes move from emitter to base

Electrons move from base to collector

Holes move from base to emitter

Holes move from emitter to base

27. In between two consecutive permissible energy bands, there is a range of energy states which cannot be occupied by electrons. These are called

Forbidden energy states

Band levels

None of these

Hidden energy states

28. Which one is forward bias?

29. The least doped region in a transistor is

Collector

Base

Emitter

30. In half wave rectification

Current flows in one directions

Current flows in pulses

Only half cycle is used

None of these

31. A signal applied at the non-inverting input, of an O.P that appears after amplification at the output terminal, with

90° Phase shift

120° Phase shift

No Phase shift

180° Phase shift

32. In the transistor schematic symbol, the arrow

Is locate on the collector

Is located on the emitter

Point from north to south

Is located on the base

33. An OP-AMP comparator is a circuit that compares the signal voltage on one of its inputs with a _

Virtual input

Reference voltage on the other

Output

Non-inverting voltage at output

34. When a p-n junction diode is reverse biased, the flow of current across the junction is mainly due to

Both drift and diffusion of charges

Depends upon the nature of material

Drift of charges

Diffusion of charges

35. In a n-p-n transistor:

Holes move from base to collector

Negative charge moves from emitter to base

Negative charge moves from collector to base

Holes move from emitter to base

36. In the middle of the depletion layer of a reverse-biased p-n junction, the

Potential is maximum

Electric field is maximum

Potential is zero

Electric field is zero

37. p-type crystal of a p-n junction diode is connected to a positive terminal of battery and n-type crystal connected to negative terminal of battery

Diode is reverse biased

Potential barrier in depletion layer remains unchanged

Diode is forward based

Potential barrier in depletion layer increases

38. n-type germanium is obtained on doping intrinsic germanium with

Phosphorus

Boron

Aluminum

Gold

39. A device for converting an alternating current into a pulsating from or direct current is known as

None of these

Detector

Oscillator

Rectifier

40. When aluminum is added as an impurity to silicon, then resulting material is

n-type conductor

p-type semiconductor

p-type conductor

n-type semiconductor

41. In a junction diode, the holes are due to

Missing of electrons

Extra electrons

Neutrons

Protons

42. Reverse bias applied on a junction diode

Increase the minority carrier current

Increases the majority carrier current

Lowers the potential barrier

Raises the potential barrier

43. Which of the following when added as an impurity into the silicon produces n-type semi-conductor?

44. In common emitter amplifier (l₀/lE) = 0.98, then current gain is

4.9

9.8

45. When NPN transistor is used as an amplifier

Electrons move from collector to base

Electrons move from emitter to base

Electrons move from base to emitter

Holes move from base to emitter

46. Semi-conductor germanium and silicon are

Tetravalent

Pentavalent

Divalent

Trivalent

47. The operation of a transistor requires

None of these

That the emitter be heated

That the base be heated

That the collector be heated

48. The output will be a LOW for any case when one or more inputs are zero in a(n):

AND gate

NOT gate

OR gate

NAND gate

49. In a PN junction

High potential at P side and low potential at N side

P and N both are at same potential

Undetermined

High potential at N side and low potential at P side

50. The ratio of applied stress to volumetric strain is called

Shear modulus

Bulk modulus

None of these

Young’s modulus

51. Electrons present in p-type material due to thermal pair generation are

Minority carriers

Dual carriers

Majority carriers

Blockers

52. When arsenic is added as an impurity to silicon, the resulting material is

None of these

N-type conductor

N-type semiconductor

P-type semiconductor

53. Depletion layer consists of

Immobile ions

Electrons

Protons

Mobile ions

54. When aluminum is added as an impurity to silicon, then resulting material is

p-type semiconductor

p-type conductor

n-type conductor

n-type semiconductor

55. If a signal passing through a gate is inhibited by sending a low into one of the inputs, and the output is HIGH, the gate is a(n):

NOR

AND

NAND

56. A NAND gate has:

None of these

LOW inputs and a LOW output

HIGH inputs and a HIGH output

LOW inputs and a HIGH output

57. The working of transistor as amplifier is similar to

Step down transformer

Step up transformer

Triode vacuum tube

Three diodes in common

58. With negative feedback, the returning signal:

Opposes the input signal

Aids the input signal

Is proportional to differential voltage gain

Is proportional to output current

59. The measure of deformation of a solid when stress is applied to it is called

None of these

Strain

Stress

Force

60. The electrical circuit used to bet smooth DC output from a rectifier circuit is called

Oscillator

Filter

Amplifier

Logic gates

61. Barrier potential of a p-n junction diode does not depend on:

Temperature

Doping density

Diode design

Forward bias

62. When n-type of semiconductor is heated,

Number of electrons and holes increases equally

Number of holes increases while that of holes decreases

Number of electrons increases while that of holes decreases

Number of electrons and holes remains same

63. p-n junction when reversed biased acts as a

Inductor

Capacitor

On switch

Off switch

64. The ratio β shows the

None of these

Current gain

Input resistance

Voltage gain

65. When n-p-n transistor is used as an amplifier

Holes move from emitter to base

Holes move from emitter be base

Electrons move from base to collector

Holes move from base to emitter

66. In p-n-p transistor the collector current is

Slightly less than emitter current

Greater than emitter current

Any of above

Equal to emitter current

67. Using OP-Amp as an inverting amplifier, the non-inverting terminal has potential

Low

None of these

Zero

High

68. A n-p-n transistor conducts when

Collector is positive and emitter is negative with respect to the base

Collector is positive and emitter is at negative potential as the base

Both collector and emitter are positive with respect to the base

Both collector and emitter are negative with respect to the base

69. Due to high loop gain of the amplifier, the inverting and non-inverting inputs are

Non-inverting terminal is at high potential

Both are at the same potential

Inverting terminal is at high potential

Both are at the high potential

70. In a n-p-n transistor:

Holes move from base to collector

Holes move from emitter to base

Negative charge moves from emitter to base

Negative charge moves from collector to base

71. The width of a depletion layer in a p-n junction is

Increased by reverse biasing

Increased by forward biasing

Decreased by reverse biasing

Is independent of voltage

72. Light emitting diode work when it is

Forward biases

Reverse biased

None of these

Both

73. In junction diode, the holes are because of:

Protons

Extra electrons

Missing electrons

Neutrons

74. In Germanium crystal, impurity donor elements have valiancy

75. When a strength changes the length of a body, it is called

Compress ional stress

Tensile stress

None of these

Shear stress

76. In junction diode, the holes are because of:

Extra electrons

Protons

Missing electrons

Neutrons

77. The gain A of the amplifier is of the order of

Hundreds

None of these

Thousands

Man hundred

78. The energy gap between conduction band and valence band is order 0.07 eV. It is a

Conductor

Alloy

Insulator

Semiconductor

79. Two inputs of NAND gates are shorted. This gate is equivalent to

XOR gate

AND gate

NOT gate

OR gate

80. A device which converts an alternating current to direct current is called

P-type material

Amplifier

Rectifier

Oscillator

81. In the middle of the depletion layer of a reverse-biased p-n junction, the

Potential is zero

Potential is maximum

Electric field is zero

Electric field is maximum

82. If positive end of battery is connected to p-side and negative end of battery is connected to n-side of diode then

Diode is reverse biased

Diode is forward biased

None of these

Diode is neutralized

83. The p-n junction diode works as insulator, if connected

To A.C.

In reverse bias

None of these

In forward bias

84. The forward resistance of the diode is

None of these

Ohms

Many ohms

Few ohms

85. In a good conductor, the energy gap between the conduction band and the valence band is

Infinity

Wide

Narrow

Zero

86. A non-inverting closed-loop op-amp circuit generally has a gain factor:

Less than one

Greater than one

Of zero

Equal to one

87. The switch is open when the resistance between C and E becomes

Almost zero

None of these

Zero

Infinity

88. At absolute zero, Si acts as

Insulator

None of these

Metal

Non-metal

89. The electrons in the outermost shell of an atom are called

Tightly bound electrons

None of these

Free electrons

Valence electrons

90. The device or circuit used for conversion of A.C. into D.C. is called

A rectifier

Filtering circuit

An amplifier

Converter

91. The energy band gap is maximum in

Semiconductors

Metals

Insulators

Superconductors

92. A pieced of copper and another of germanium are cooled from room temperature to 77 K, the resistance of

Copper increases and germanium decreases

Each of them increases

Copper decreases and germanium increases

Each of them decreases

93. The critical temperature for mercury is

7.2 K

1.18 K

3.72 K

4.2 K

94. Zener breakdown in a semiconductor diode occurs when

Forward bias exceeds certain value

Forward current exceeds certain value

Reverse bias exceeds certain value

Potential barrier is reduced to zero

95. The especially designed semiconductor diodes used as indicator lamps in electronic circuits are

Solar cells

The photo diodes

The switch

The light emitting diode

96. The whole structure obtained by the repetition of unit cell is known as

Crystal lattice

Unit cell

Ore

All of these

97. A photodiode can turn its current ON and OFF in

Microsecond

None of these

Millisecond

Nanosecond

98. In a p-type semiconductor germanium is doped with:

Gallium

Aluminum

Boron

All of above

99. Suitable impurities are added to a semiconductor depending on its use. This is due to:

Enable it to Telerate higher voltage

Increase its life

Increase its electrical resistivity

Increases its electrical conductivity

100. Copper and germanium are cooled to 70 K from room temperature, then

Resistance of both decreases

Resistance of copper decreases while that of germanium increases

Resistance of both increases

Resistance of copper increases while that of germanium decreases

101. In a p-type semiconductor germanium is doped with:

Gallium

Aluminum

All of these

Boron

102. The transistor provide good power amplification when they are used in

Common base configuration

Common collector configuration

Common emitter configuration

None of these

103. In p – n junction, after diffusion, a charge less region is formed around the junction is called

Diffusion region

Charged region

Depletion region

None of these

104. The impurity atoms with which a pure silicon should be doped to make a p-type semiconductor is

Antimony

Aluminum

Arsenic

Phosphorus

105. Arsenic, antimony or phosphorus are impurities of

None of these

may be p-type or n-type

p-type

n-type

106. When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called

n-type

Intrinsic

Extrinsic

p-type

107. The potential difference across the depletion region of silicon is

0.9 V

0.5 V

0.7 V

0.67 V

108. When a semiconductor is continuously heated, then value of its resistance

Remains unchanged

Increases

Decreases

Decreases and then increases

109. Transistor can be used as

Filter

Full wave rectifier

Half wave rectifier

Amplifier

110. At room temperature, a p-type semi-conductor has

Large number of free electrons and few holes

Equal number of free electrons and holes

Large number of holes and electrons

Large number of holes and few electrons

111. Depletion region of a junction is formed

Under reverse bias

Under forward bias

During the manufacturing process

When temperature varies

112. The width of a depletion layer in a p-n junction is

Increased by reverse biasing

Increased by forward biasing

Decreased by reverse biasing

Is independent of voltage

113. The units of modulus of elasticity are same as that of

None of these

Force

Strain

Stress

114. A junction between p-type material and n-type material is called as

Rectifier

Transistor

Diode

Amplifier

115. The semiconductor diode can be used as a rectifier because _

Its conductivity increases with rise of temperature

It has high resistance to the current flow when reverse biased

It has low resistance to the current flow when forward biased & high resistance when reverse biased

It has low resistance to the current flow when forward biased

116. Application of photodiode is/are

Detection of visible and invisible radiations

Logic gates

None of these

Automatic switching

117. The least doped region in a transistor is

Either emitter or collector

Collector

Emitter

Base

118. Photovoltaic cell produces electrical energy from

Heat energy

Light energy

None of these

Chemical energy

119. A piece of copper and another of germanium are cooled from room temperature to 77 K, the resistance of

Copper decreases and germanium increases

Each of them decreases

Each of them increases

Copper increases and germanium decreases

120. Reverse bias applied on a junction diode

Increase the minority carrier current

Increases the majority carrier current

Lowers the potential barrier

Raises the potential barrier

121. A p-n junction has a thickness of the order of:

10¯¹² cm

10¯⁶ cm

1 mm

1 cm

122. In p-type semiconductor

Major current carrier is electrons

The number of mobile holes exceeds the number of acceptors

Major carrier is mobile negative ions

Major carrier is mobile holes

123. In insulators

Conduction band is empty and valence band is filled with electrons

Conduction band is partially filled with electrons

Conduction band is filled with electrons and valence band is empty

Valence band is partially filled with electrons

124. The part of a transistor which is most heavily doped to produce large number of majority carriers is

Can be any of the above three

Collector

Emitter

Base

125. In comma emitter amplifier (l₀/lE) = 0.98, then current gain is

9.8

4.9

126. n-type semiconductor if formed

From pure Ge crystal

From pure Si crystal

When a Ge crystal is doped with an impurity containing 3 valence electrons

When a Ge crystal is doped with an impurity containing 5 valence electrons

127. At room temperature, a p-type semi-conductor has

Equal number of free electrons and holes

Large number of holes and electrons

Large number of holes and few electrons

Large number of free electrons and few holes

128. The number of junctions in the PNP transistor are

129. Polythene, potystrene and nylon are examples of

Glassy solids

Crystalline solids

Amorphous solids

Polymeric solids

130. A substance which have empty conduction band is called

Semiconductor

None of these

Conductor

Insulator

131. What input values will cause an AND logic gate to produce a HIGH output?

At least one input is HIGH

All inputs are HIGH

At least one input is LOW

All inputs are LOW

132. NAND gate is

A basic gate

Not a universal gate

A basic universal gate

A universal gate

133. In a semiconductor, the mobility of holes is

Less than electrons

Greater than electrons

Equal to electrons

None

134. In n-p-n transistor, p works as

Collector

Base

Any of above

Emitter

135. In a P-type semiconductor

Major current carriers are mobile holes

The no. of mobile holes exceeds the no. of mobile acceptors

Major current carriers are mobile negative ions

Major current carriers are electrons

136. The part of a transistor, which is heavily doped to produce a large number of majority carriers, is

Emitter

Collector

None of these

Base

137. When boron is added as an impurity to silicon, the resulting material is:

n-type conductor

p-type conductor

n-type semiconductor

p-type semiconductor

138. A single transistor can be used to build which of the following digital logic gates?

NOT gates

AND gates

OR gates

NAND gates

139. Transistors with various combinations are widely used as switches in:

Transformers

Computers

Electric generations

Electric motors

140. In Germanium crystal, impurity donor elements have valiancy

141. In forward bias the width of potential barrier

Remains same

No effect

Increases

Decreases

142. The electrical circuit used to have smooth DC output from a rectifier circuit is called

Logic gates

Filter

Amplifier

Oscillator

143. The energy band gap is maximum in

Semiconductors

Superconductors

Metals

Insulators

144. Due to the break down the p-n junction suffers

Require more current

Damaged

None of these

Works efficiently

145. Identify the correct statement about minority carriers

Holes in n-type and free electrons in p-type

Free electrons in n-type and holes in p-type

Holes in n-type and p-type

Free electrons in n-type and p-type

146. Diode can work as

Modulator

Oscillator

Rectifier

Multivibrator

147. Suitable impurities are added to a semiconductor depending on its use. This is due to

Increase its electrical resistivity

Increase its electrical conductivity

Enable it to Telerate higher voltage

Increase its life

148. Acceptor and donor impurities donate

p-carriers only

n-carriers and p-carriers respectively

p-carriers and n-carriers respectively

n-carriers only

149. Semi-conductors with donor atoms and free electrons belong to the type

mix

any of above

150. The simplest type of rectification known as half wave rectification is obtained by

Suppressing the harmonics in A.C voltage

Suppressing half wave of A.C supply by using diode

Using a Coolidge tube

Using a transistor

151. In n-type substances, the minority carriers are

Neutrons

Holes

None of these

Electrons

152. The impurity atoms with which a pure silicon should be doped to make a p-type semiconductor is

Arsenic

Phosphorus

Aluminum

Antimony

153. In a P-type semiconductor

Major current carriers are electrons

Major current carriers are mobile negative ions

Major current carriers are mobile holes

The no. of mobile holes exceeds the no. of mobile acceptors

154. Conversion of low input a.c. into high output a.c. is called:

All of these

Rectification

Amplification

Magnification

155. The ratio of tensile stress to tensile strain is called

None of these

Bulk’s modulus

Young’s modulus

Modulus of electricity

156. Radio waves of constant amplitude can be generated with

Rectifier

Filter

FET

Oscillator

157. In reverse biasing of p-n junction, the resistance offered by the diode is of the order of

Several mega ohms

Kilo ohms

Ohms

Mega ohms

158. The electromagnetic waves emitted by the LC circuit of areal to a transmitting station are of

Unit amplitude

Variable amplitude

Constant amplitude

Zero amplitude

159. When a pentavalent material like As, is added to tetravalent material l.e. Ge, we get a

P-type material

N-type material

Super conductor

Semiconductor

160. In semiconductors at a room temperature

The conduction band is completely empty

The valence band is completely filled and the conduction band is partially filled

The valence band is completely filled

The valence band is partially empty and the conduction band is partially filled

161. Exclusive-OR (XOR) logic gates can be constructed from what other logic gates?

AND gates and NOT gates

OR gates only

AND gates, OR gates, and NOT gates

Or gates and NOT gates

162. At absolute zero, Si acts as

Insulator

Non-metal

Metal

None of these

163. N-type crystal is

Neutral

Negative charged

None of these

Positively charged

164. The positive sign of gain indicates that

None of these

Input and out signals are in phase

Input and out signals are not in phase

May be in phase or not

165. Symbol represents

NAND gate

XNOR gate

NOT gate

NOR gate

166. Which one is reverse-biased?

167. An OP-AMPs can amplify

Both A.C. & D.C.

A.C.

None of these

D.C.

168. A transistor consists of

Four PN-junctions

Three PN-junctions

One PN-junction

Two PN-junctions

169. LDR means:

Low degree radiations

Low degree resistor

Light dependent resistance

None of these

170. Which logic gate is represented by following diagram?

AND

NOR

EOR

171. When the output of OR gate is 1

If both inputs are zero

If either or both inputs are 1

If either input is zero

Only if both inputs are 1

172. To use a transistor as an amplifier

Both junctions are reverse biased

No bias voltages are required

The emitter base junction is forward biased and the base collector junction is reverse biased

Both junctions are forward biased

173. The basic logic gate whose output is the complement of the input is the:

OR gate

INVERTER gate

Comparator

AND gate

174. In semiconductors at a room temperature

The conduction band is completely empty

The valence band is completely filled and the conduction band is partially filled

The valence band is partially empty and the conduction band is partially filled

The valence band is completely filled

175. In p-type semi-conductor, the majority charge carriers are

Electrons

Neutrons

Protons

Holes

176. Which is normal used of transistor?

Diode

P-type material

Switching device

Rectifier

177. When an alternating accelerating field is applied to a charge it produces

Electromagnetic Waves

Transverse Waves

x-rays

Gamma Rays

More Related Resources

Punjab 12th Class Physics Chapter 7... Punjab 10th Class Physics Chapter 7... 10th Class Physics Chapter 7 Basic ... Punjab Physics Online Test 10th Cla... Punjab Physics Online Test 12th Cla... KPK Board 10th Class Physics Ch 7 I... KPK Board 12th class Physics Ch 17 ... 12th Class Physics CHAPTER 7 ELECTR... Physics Optics Online Mcqs Test Physics 10 Class textbook Download ...

Can't find what you're looking for? Search below:

Latest Updates

Punjab Physics Online Test 10th Class Chapter 7 Basic Electronics
Punjab Physics Online Test 12th Class Chapter 7 Electronics
Physics Optics Online Mcqs Test
Physics 10 Class textbook Download Online [ Punjab Board]
PPSC Syllabus for Physics Lecturer 2026 Sample Test Pattern
PAF-KIET Entry Test 2026 Preparation Online MCQS Test English Mat...

Malik TahirLast Updated: October 13, 2025

Important Electronics Question and Answer

Physics Electronics Practice Test Online With Explanation

More Related Resources

Latest Updates

Malik Tahir

Leave a Reply Cancel reply