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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.
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Physics Electronics Practice Test Online With Explanation

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1. Symbol represents

NAND gate

NOT gate

NOR gate

XNOR gate

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

n-type semiconductor

p-type conductor

n-type conductor

p-type semiconductor

3. Arsenic, antimony or phosphorus are impurities of

may be p-type or n-type

p-type

None of these

n-type

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

None of these

Microsecond

Nanosecond

Millisecond

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

Resistor is used

Capacitor is used

Solvent is used

None of these

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

Superconductors

Semiconductors

Conductors

Insulators

7. Diode can work as

Oscillator

Rectifier

Modulator

Multivibrator

8. 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

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

Output

Reference voltage on the other

Non-inverting voltage at output

Virtual input

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

None of these

Works efficiently

Damaged

Require more current

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

Insulator

n-type

Superconductor

p-type

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

None of these

Diode is reverse biased

Diode is forward biased

Diode is neutralized

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

4.9

9.8

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

OR gates

NAND gates

NOT gates

AND gates

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

Almost zero

Zero

None of these

Infinity

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

Neutrons

Extra electrons

Protons

Missing of electrons

17. Acceptor and donor impurities donate

p-carriers only

n-carriers only

n-carriers and p-carriers respectively

p-carriers and n-carriers respectively

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

Increases

Remains unchanged

Decreases

Decreases and then increases

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

Of zero

Less than one

Greater than one

Equal to one

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

Any of the above depending on nature of transistor

Collector

Emitter

Base

21. A transistor consists of

Three PN-junctions

Two PN-junctions

Four PN-junctions

One PN-junction

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

None of these

Holes

Neutrons

Electrons

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

Increased by reverse biasing

Decreased by reverse biasing

Is independent of voltage

Increased by forward biasing

24. Depletion region of a junction is formed

Under forward bias

When temperature varies

During the manufacturing process

Under reverse bias

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

Increases

First A and B

Decreases

Remains constant

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

Neutrons

Protons

Missing electrons

Extra electrons

27. In the transistor schematic symbol, the arrow

Point from north to south

Is located on the base

Is located on the emitter

Is locate on the collector

28. The energy band gap is maximum in

Superconductors

Semiconductors

Insulators

Metals

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

Equal number of free electrons and holes

Large number of free electrons and few holes

Large number of holes and few electrons

Large number of holes and electrons

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

Modulus of electricity

Young’s modulus

None of these

Bulk’s modulus

31. In a P-type semiconductor

Major current carriers are electrons

Major current carriers are mobile holes

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

Major current carriers are mobile negative ions

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

Stress

Strain

Force

None of these

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

4.9

9.8

34. LDR means:

None of these

Low degree radiations

Light dependent resistance

Low degree resistor

35. In p-type semiconductor

Major current carrier is electrons

Major carrier is mobile holes

Major carrier is mobile negative ions

The number of mobile holes exceeds the number of acceptors

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

Ohms

Kilo ohms

Several mega ohms

Mega ohms

37. At absolute zero, Si acts as

Non-metal

Insulator

Metal

None of these

38. N-type crystal is

None of these

Neutral

Positively charged

Negative charged

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

None of these

It offers a very high inputs resistance to the input current

It offers a very low output resistance

It offers a very low open loop gain all of above

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

Electrons move from base to collector

Holes move from emitter to base

Holes move from base to emitter

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

P-type material

Rectifier

Amplifier

Oscillator

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

Unit amplitude

Variable amplitude

Zero amplitude

Constant amplitude

43. Depletion layer consists of

Electrons

Mobile ions

Protons

Immobile ions

44. A substance which have empty conduction band is called

Semiconductor

Insulator

None of these

Conductor

45. The energy band gap is maximum in

Metals

Insulators

Semiconductors

Superconductors

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

Increase its life

Increase its electrical resistivity

Increases its electrical conductivity

Enable it to Telerate higher voltage

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

Increased by reverse biasing

Increased by forward biasing

Is independent of voltage

Decreased by reverse biasing

48. 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

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

Resistance of copper decreases while that of germanium increases

Resistance of both decreases

Resistance of copper increases while that of germanium decreases

Resistance of both increases

50. The ratio β represents

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

Minority carriers

Majority carriers

Dual carriers

Blockers

52. Reverse bias applied on a junction diode

Lowers the potential barrier

Increase the minority carrier current

Increases the majority carrier current

Raises the potential barrier

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

Zero

Very low

Very high

Almost negligible

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

Transistor

Rectifier

Amplifier

Diode

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

Common emitter configuration

Common base configuration

None of these

Common collector configuration

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

Hundreds

Thousands

Man hundred

None of these

57. When n-type of semiconductor is heated,

Number of holes increases while that of holes decreases

Number of electrons and holes increases equally

Number of electrons increases while that of holes decreases

Number of electrons and holes remains same

58. In forward bias the width of potential barrier

No effect

Remains same

Decreases

Increases

59. The thickness of the base is equal to

Thickness of emitter

Thickness of collector

Mean of thickness of emitter and collector

Very small as compared to the thickness of emitter and collector

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

Super conductor

Semiconductor

P-type material

N-type material

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

Stress

None of these

Force

Strain

62. 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

OR gate

NOT gate

NOR gate

63. In a P-type semiconductor

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

Major current carriers are mobile holes

Major current carriers are electrons

Major current carriers are mobile negative ions

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

Base

Can be any of the above three

Emitter

Collector

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

Phosphorus

Antimony

Indium

Arsenic

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

Increase its electrical resistivity

Increase its life

Increase its electrical conductivity

Enable it to Telerate higher voltage

67. Transistor can be used as

Half wave rectifier

Full wave rectifier

Amplifier

Filter

68. Non-inverting amplifier circuits have

None of these

A very high input impedance

A low output impedance

A very low input impedance

69. 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

Zero biased

None of these

Reversed biased

Forward biased

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

Increase the majority carrier current

Raises the potential barrier

Lowers the potential barrier

Increase the minority carrier current

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

Phosphorus

Aluminum

Arsenic

Antimony

72. In semiconductors at a room temperature

The valence band is completely filled

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 conduction band is completely empty

73. The positive sign of gain indicates that

Input and out signals are not in phase

Input and out signals are in phase

None of these

May be in phase or not

74. 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

Base

Collector

Emitter

75. The number of junctions in the PNP transistor are

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

Detector

Rectifier

None of these

Oscillator

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

Conductor

Alloy

Insulator

Semiconductor

78. Identify the correct statement about minority carriers

Free electrons in n-type and p-type

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

Holes in n-type and p-type

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

79. The least doped region in a transistor is

Collector

Emitter

Base

Either emitter or collector

80. Which one is reverse-biased?

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

1 mm

10¯⁶ cm

10¯¹² cm

1 cm

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

AND gate

OR gate

NOT gate

XOR gate

83. A NAND gate has:

LOW inputs and a HIGH output

LOW inputs and a LOW output

HIGH inputs and a HIGH output

None of these

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

Low

None of these

Zero

High

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

Any of above

Slightly less than emitter current

Equal to emitter current

Greater than emitter current

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

Any of above

Collector

Emitter

Base

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

Extra electrons

Missing electrons

Protons

Neutrons

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

NAND gate

NOT gate

AND gate

OR gate

89. Radio waves of constant amplitude can be generated with

Oscillator

Rectifier

Filter

FET

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

Decreases slowly

Suddenly increases

Increases slowly

Remain fixed

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

Copper increases and germanium decreases

Copper decreases and germanium increases

Each of them increases

Each of them decreases

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

AND gates, OR gates, and NOT gates

Or gates and NOT gates

OR gates only

AND gates and NOT gates

93. A n-p-n transistor conducts when

Both collector and emitter are positive with respect to the base

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

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

Both collector and emitter are negative with respect to the base

94. Photovoltaic cell produces electrical energy from

Heat energy

None of these

Chemical energy

Light energy

95. To use a transistor as an amplifier

No bias voltages are required

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

Both junctions are reverse biased

Both junctions are forward biased

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

Young’s modulus

None of these

Bulk modulus

Shear modulus

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

Filtering circuit

An amplifier

Converter

A rectifier

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

Phosphorus

Arsenic

Antimony

Aluminum

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

No Phase shift

90° Phase shift

180° Phase shift

120° Phase shift

100. In semiconductors at a room temperature

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

The conduction band is completely empty

101. Semi-conductor germanium and silicon are

Pentavalent

Divalent

Tetravalent

Trivalent

102. Polythene, potystrene and nylon are examples of

Amorphous solids

Crystalline solids

Glassy solids

Polymeric solids

103. With negative feedback, the returning signal:

Is proportional to output current

Opposes the input signal

Is proportional to differential voltage gain

Aids the input signal

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

Compress ional stress

Shear stress

None of these

Tensile stress

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

In reverse bias

None of these

To A.C.

In forward bias

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

Narrow

Zero

Wide

Infinity

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

It has low resistance to the current flow when forward biased

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

Its conductivity increases with rise of temperature

It has high resistance to the current flow when reverse biased

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

All inputs are HIGH

At least one input is HIGH

At least one input is LOW

All inputs are LOW

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

Both are at the high potential

Both are at the same potential

Inverting terminal is at high potential

Non-inverting terminal is at high potential

110. The forward resistance of the diode is

Many ohms

Few ohms

None of these

Ohms

111. A diode as a rectifier converts:

D.C. into A.C.

High voltage to low voltage

A.C. into D.C.

Low voltage to high voltage

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

Valence electrons

Tightly bound electrons

None of these

Free electrons

113. In half wave rectification

Current flows in one directions

Current flows in pulses

Only half cycle is used

None of these

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

Holes

Electrons

Neutrons

Protons

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

Holes move from emitter be base

Holes move from base to emitter

Holes move from emitter to base

Electrons move from base to collector

116. In insulators

Valence band is partially filled with electrons

Conduction band is filled with electrons and valence bad is empty

Conduction band is empty and valence band is filled with electrons

Conduction band is partially filled with electrons

117. The critical temperature for mercury is

4.2 K

7.2 K

3.72 K

1.18 K

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

0.5 V

0.7 V

0.9 V

0.67 V

119. In insulators

Conduction band is empty and valence band is filled with electrons

Conduction band is filled with electrons and valence band is empty

Conduction band is partially filled with electrons

Valence band is partially filled with electrons

120. Photodiode is used for

None of these

Light display

Detection of light

Emission of light

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

Amplifier

Filter

Logic gates

Oscillator

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

Unit cell

Crystal lattice

All of these

Ore

123. 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

NAND

AND

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

Equal number of free electrons and holes

Large number of free electrons and few holes

Large number of holes and few electrons

Large number of holes and electrons

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

n-type semiconductor

n-type conductor

p-type conductor

p-type semiconductor

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

Extrinsic

Intrinsic

n-type

p-type

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

x-rays

Gamma Rays

Electromagnetic Waves

Transverse Waves

128. NAND gate is

A universal gate

Not a universal gate

A basic universal gate

A basic gate

129. In a semiconductor, the mobility of holes is

Equal to electrons

Less than electrons

None

Greater than electrons

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

Amplification

Magnification

All of these

Rectification

131. Which is normal used of transistor?

Rectifier

Switching device

Diode

P-type material

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

Each of them increases

Copper decreases and germanium increases

Copper increases and germanium decreases

Each of them decreases

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

Extrinsic

p-type

n-type

Intrinsic

134. A diode as a rectifier converts:

High voltage to low voltage

D.C. into A.C.

Low voltage to high voltage

A.C. into D.C.

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

Potential is maximum

Potential is zero

Electric field is maximum

Electric field is zero

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

Comparator

OR gate

INVERTER gate

AND gate

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

All of above

Boron

Gallium

Aluminum

138. Light emitting diode work when it is

Both

Reverse biased

None of these

Forward biases

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

Drift of charges

Both drift and diffusion of charges

Depends upon the nature of material

Diffusion of charges

140. The working of transistor as amplifier is similar to

Step up transformer

Step down transformer

Triode vacuum tube

Three diodes in common

141. 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

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

None of these

Emitter

Collector

Base

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

Increases

Remains unchanged

Decreases and then increases

Decreases

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

Superconductor

Semiconductor

Insulator

None of these

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

Electric field is zero

Potential is maximum

Potential is zero

Electric field is maximum

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

Electrons and protons

Electrons and holes

Protons and electrons

Holes and electrons

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

None of these

Charged region

Diffusion region

Depletion region

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

n-type semiconductor

p-type semiconductor

n-type conductor

p-type conductor

149. The ratio β shows the

Current gain

None of these

Input resistance

Voltage gain

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

Electric generations

Computers

Transformers

Electric motors

151. The least doped region in a transistor is

Emitter

Base

Collector

152. 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 forward based

Diode is reverse biased

Potential barrier in depletion layer remains unchanged

Potential barrier in depletion layer increases

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

any of above

mix

154. At absolute zero, Si acts as

Metal

Insulator

None of these

Non-metal

155. 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

156. Application of photodiode is/are

Logic gates

Detection of visible and invisible radiations

None of these

Automatic switching

157. An OP-AMPs can amplify

A.C.

Both A.C. & D.C.

D.C.

None of these

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

P-type semiconductor

N-type semiconductor

None of these

N-type conductor

159. Which logic gate is represented by following diagram?

EOR

NOR

AND

160. In a n-p-n transistor:

Negative charge moves from emitter to base

Holes move from emitter to base

Negative charge moves from collector to base

Holes move from base to collector

161. In Germanium crystal, impurity donor elements have valiancy

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

Phosphorus

Aluminum

Boron

Gold

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

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

Aluminum

Boron

All of these

Gallium

165. Which one is forward bias?

166. In a PN junction

High potential at N side and low potential at P side

Undetermined

High potential at P side and low potential at N side

P and N both are at same potential

167. In Germanium crystal, impurity donor elements have valiancy

168. Young’s modulus for copper is

70 x 10 Nm¯²

91 x 10 Nm¯²

110 Nm¯²

None of these

169. 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

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

Doping density

Diode design

Forward bias

Temperature

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

The photo diodes

Solar cells

The switch

The light emitting diode

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

Using a transistor

Using a Coolidge tube

Suppressing half wave of A.C supply by using diode

Suppressing the harmonics in A.C voltage

173. When the output of OR gate is 1

If either input is zero

Only if both inputs are 1

If both inputs are zero

If either or both inputs are 1

174. The operation of a transistor requires

That the emitter be heated

That the collector be heated

None of these

That the base be heated

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

Inductor

On switch

Capacitor

Off switch

176. In a n-p-n transistor:

Negative charge moves from collector to base

Holes move from emitter to base

Negative charge moves from emitter to base

Holes move from base to collector

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

Oscillator

Filter

Amplifier

Logic gates

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Malik TahirLast Updated: October 13, 2025

Physics Electronics Online Mcqs Test

Important Electronics Question and Answer

Physics Electronics Practice Test Online With Explanation

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