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ECAT Physics Electronics MCQS Online Test

Maan AliLast Updated: April 19, 2025

Physics Electronics MCQS Online Test

ECAT Physics Electronics Chapter Online Test

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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1. 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 electrons

Large number of holes and few electrons

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

Enable it to Telerate higher voltage

Increase its electrical resistivity

Increases its electrical conductivity

Increase its life

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

Reference voltage on the other

Output

Virtual input

Non-inverting voltage at output

4. Which one is forward bias?

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

Increased by forward biasing

Decreased by reverse biasing

Increased by reverse biasing

Is independent of voltage

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

Young’s modulus

None of these

Modulus of electricity

Bulk’s modulus

7. 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

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

Zero

Almost zero

Infinity

None of these

9. A diode as a rectifier converts:

D.C. into A.C.

A.C. into D.C.

High voltage to low voltage

Low voltage to high voltage

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

Transformers

Computers

Electric generations

Electric motors

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

Missing electrons

Protons

Extra electrons

Neutrons

12. The critical temperature for mercury is

7.2 K

1.18 K

3.72 K

4.2 K

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

Resistance of copper increases while that of germanium decreases

Resistance of both increases

Resistance of both decreases

Resistance of copper decreases while that of germanium increases

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

Aluminum

Phosphorus

Antimony

Arsenic

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

Require more current

None of these

Damaged

Works efficiently

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

Equal to one

Of zero

Less than one

Greater than one

17. Which logic gate is represented by following diagram?

AND

NOR

EOR

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

Neutrons

Protons

Missing of electrons

Extra electrons

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

Emitter

Collector

Any of the above depending on nature of transistor

Base

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

Or gates and NOT gates

OR gates only

AND gates, OR gates, and NOT gates

AND gates and NOT gates

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

Copper decreases and germanium increases

Copper increases and germanium decreases

Each of them increases

Each of them decreases

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

Both are at the high potential

Non-inverting terminal is at high potential

Both are at the same potential

Inverting terminal is at high potential

23. Arsenic, antimony or phosphorus are impurities of

p-type

None of these

may be p-type or n-type

n-type

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

Comparator

AND gate

INVERTER gate

OR gate

25. 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

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

It offers a very low output resistance

It offers a very high inputs resistance to the input current

None of these

It offers a very low open loop gain all of above

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

N-type material

Super conductor

Semiconductor

P-type material

28. NAND gate is

A basic gate

A universal gate

Not a universal gate

A basic universal gate

29. With negative feedback, the returning signal:

Opposes the input signal

Is proportional to differential voltage gain

Aids the input signal

Is proportional to output current

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

High

Zero

None of these

Low

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

32. Reverse bias applied on a junction diode

Lowers the potential barrier

Raises the potential barrier

Increase the minority carrier current

Increases the majority carrier current

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

Remains unchanged

Decreases

Decreases and then increases

Increases

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

All inputs are HIGH

At least one input is LOW

All inputs are LOW

At least one input is HIGH

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

Kilo ohms

Ohms

Several mega ohms

Mega ohms

36. The energy band gap is maximum in

Superconductors

Semiconductors

Insulators

Metals

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

Almost negligible

Very high

Very low

Zero

38. The least doped region in a transistor is

Base

Either emitter or collector

Collector

Emitter

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

Rectifier

None of these

Detector

Oscillator

40. In semiconductors at a room temperature

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

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

The conduction band is completely empty

The valence band is completely filled

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

Extrinsic

n-type

Intrinsic

p-type

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

Remains unchanged

Decreases and then increases

Increases

Decreases

43. 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

180° Phase shift

No Phase shift

44. 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

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

Neutrons

Holes

Electrons

Protons

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

First A and B

Increases

Remains constant

Decreases

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

None of these

Resistor is used

Capacitor is used

Solvent is used

48. 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 neutralized

Diode is reverse biased

Diode is forward biased

None of these

49. 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

Drift of charges

Diffusion of charges

Depends upon the nature of material

50. 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

Collector

Base

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

Using a transistor

Suppressing the harmonics in A.C voltage

Using a Coolidge tube

Suppressing half wave of A.C supply by using diode

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

Shear modulus

Young’s modulus

Bulk modulus

None of these

53. The number of junctions in the PNP transistor are

54. At absolute zero, Si acts as

Insulator

None of these

Metal

Non-metal

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

Its conductivity increases with rise of temperature

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

It has high resistance to the current flow when reverse biased

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

Insulator

Alloy

Conductor

Semiconductor

57. In p-type semiconductor

The number of mobile holes exceeds the number of acceptors

Major carrier is mobile holes

Major current carrier is electrons

Major carrier is mobile negative ions

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

Holes move from base to emitter

Electrons move from base to collector

Holes move from emitter to base

59. In a n-p-n transistor:

Holes move from base to collector

Negative charge moves from collector to base

Holes move from emitter to base

Negative charge moves from emitter to base

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

OR gate

NOR gate

AND gate

NOT gate

61. Acceptor and donor impurities donate

p-carriers and n-carriers respectively

n-carriers only

p-carriers only

n-carriers and p-carriers respectively

62. Symbol represents

NOR gate

NOT gate

XNOR gate

NAND gate

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

Amplification

All of these

Rectification

Magnification

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

Collector

Base

Can be any of the above three

Emitter

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

Intrinsic

Extrinsic

p-type

n-type

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

XOR gate

AND gate

NOT gate

OR gate

67. Depletion region of a junction is formed

Under forward bias

During the manufacturing process

Under reverse bias

When temperature varies

68. When NPN transistor is used as an amplifier

Electrons move from emitter to base

Electrons move from collector to base

Electrons move from base to emitter

Holes move from base to emitter

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

Variable amplitude

Unit amplitude

Zero amplitude

Constant amplitude

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

4.9

9.8

71. At absolute zero, Si acts as

Non-metal

Insulator

Metal

None of these

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

0.5 V

0.7 V

0.9 V

0.67 V

73. Semi-conductor germanium and silicon are

Trivalent

Tetravalent

Pentavalent

Divalent

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

Wide

Infinity

Narrow

Zero

75. LDR means:

Light dependent resistance

Low degree radiations

Low degree resistor

None of these

76. In Germanium crystal, impurity donor elements have valiancy

77. The ratio β represents

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

The switch

Solar cells

The light emitting diode

The photo diodes

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

Amplifier

Logic gates

Filter

Oscillator

80. 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):

AND

NOR

NAND

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

4.9

9.8

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

A rectifier

An amplifier

Converter

Filtering circuit

83. A NAND gate has:

None of these

HIGH inputs and a HIGH output

LOW inputs and a HIGH output

LOW inputs and a LOW output

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

Amplifier

P-type material

Rectifier

Oscillator

85. To use a transistor as an amplifier

Both junctions are reverse biased

Both junctions are forward biased

No bias voltages are required

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

86. Application of photodiode is/are

Detection of visible and invisible radiations

Automatic switching

Logic gates

None of these

87. Young’s modulus for copper is

110 Nm¯²

None of these

91 x 10 Nm¯²

70 x 10 Nm¯²

88. Zener breakdown in a semiconductor diode occurs when

Reverse bias exceeds certain value

Forward bias exceeds certain value

Potential barrier is reduced to zero

Forward current exceeds certain value

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

Boron

Gold

Phosphorus

Aluminum

90. Radio waves of constant amplitude can be generated with

Oscillator

Filter

FET

Rectifier

91. In semiconductors at a room temperature

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

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

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

Increase the minority carrier current

Increase the majority carrier current

Raises the potential barrier

Lowers the potential barrier

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

Strain

Force

None of these

Stress

94. The least doped region in a transistor is

Base

Emitter

Collector

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

NOT gates

OR gates

NAND gates

AND gates

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

Phosphorus

Indium

Arsenic

Antimony

97. A transistor consists of

Two PN-junctions

Four PN-junctions

Three PN-junctions

One PN-junction

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

Capacitor

Inductor

Off switch

On switch

99. An OP-AMPs can amplify

A.C.

Both A.C. & D.C.

None of these

D.C.

100. A diode as a rectifier converts:

A.C. into D.C.

Low voltage to high voltage

D.C. into A.C.

High voltage to low voltage

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

any of above

mix

102. The forward resistance of the diode is

Many ohms

None of these

Ohms

Few ohms

103. 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

Forward biased

Reversed biased

None of these

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

NOT gate

OR gate

AND gate

NAND gate

105. In a semiconductor, the mobility of holes is

None

Less than electrons

Equal to electrons

Greater than electrons

106. Diode can work as

Multivibrator

Rectifier

Modulator

Oscillator

107. In insulators

Conduction band is filled with electrons and valence bad is empty

Valence band is partially filled with electrons

Conduction band is empty and valence band is filled with electrons

Conduction band is partially filled with electrons

108. The operation of a transistor requires

That the base be heated

That the collector be heated

That the emitter be heated

None of these

109. 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

Potential barrier in depletion layer increases

Potential barrier in depletion layer remains unchanged

Diode is reverse biased

Diode is forward based

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

Decreased by reverse biasing

Increased by reverse biasing

Is independent of voltage

Increased by forward biasing

111. 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

112. In a PN junction

P and N both are at same potential

High potential at N side and low potential at P side

Undetermined

High potential at P side and low potential at N side

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

Common base configuration

Common emitter configuration

None of these

Common collector configuration

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

p-type semiconductor

n-type semiconductor

p-type conductor

n-type conductor

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

Doping density

Temperature

Diode design

Forward bias

116. In insulators

Conduction band is partially filled with electrons

Conduction band is filled with electrons and valence band is empty

Conduction band is empty and valence band is filled with electrons

Valence band is partially filled with electrons

117. In half wave rectification

Only half cycle is used

Current flows in pulses

Current flows in one directions

None of these

118. In Germanium crystal, impurity donor elements have valiancy

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

None of these

Thousands

Hundreds

Man hundred

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

Insulator

Semiconductor

Superconductor

None of these

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

Electrons move from base to collector

Holes move from emitter be base

Holes move from base to emitter

Holes move from emitter to base

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

Superconductor

Insulator

p-type

n-type

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

Electromagnetic Waves

Transverse Waves

Gamma Rays

x-rays

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

Any of above

Slightly less than emitter current

Greater than emitter current

Equal to emitter current

125. Which is normal used of transistor?

Switching device

Diode

P-type material

Rectifier

126. Photodiode is used for

None of these

Emission of light

Light display

Detection of light

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

P-type semiconductor

N-type conductor

None of these

N-type semiconductor

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

Gallium

Boron

Aluminum

All of above

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

10¯⁶ cm

10¯¹² cm

1 cm

1 mm

130. In forward bias the width of potential barrier

No effect

Remains same

Increases

Decreases

131. A n-p-n transistor conducts when

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

Both collector and emitter are negative with respect to the base

Both collector and emitter are positive with respect to the base

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

132. Non-inverting amplifier circuits have

A very high input impedance

A very low input impedance

A low output impedance

None of these

133. Which one is reverse-biased?

134. Depletion layer consists of

Immobile ions

Electrons

Protons

Mobile ions

135. Transistor can be used as

Filter

Half wave rectifier

Full wave rectifier

Amplifier

136. A substance which have empty conduction band is called

Insulator

Conductor

None of these

Semiconductor

137. Light emitting diode work when it is

Both

Forward biases

Reverse biased

None of these

138. The ratio β shows the

None of these

Voltage gain

Input resistance

Current gain

139. In the transistor schematic symbol, the arrow

Is locate on the collector

Is located on the emitter

Is located on the base

Point from north to south

140. 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 mobile negative ions

Major current carriers are electrons

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

Missing electrons

Protons

Neutrons

Extra electrons

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

Depletion region

Charged region

None of these

Diffusion region

143. In a n-p-n transistor:

Holes move from emitter to base

Holes move from base to collector

Negative charge moves from collector to base

Negative charge moves from emitter to base

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

Majority carriers

Dual carriers

Blockers

Minority carriers

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

Base

Emitter

Collector

None of these

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

All of these

Boron

Gallium

Aluminum

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

Valence electrons

Free electrons

None of these

Tightly bound electrons

148. A piece 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 decreases

Copper decreases and germanium increases

Each of them increases

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

Potential is zero

Electric field is zero

Electric field is maximum

Potential is maximum

150. The working of transistor as amplifier is similar to

Triode vacuum tube

Three diodes in common

Step up transformer

Step down transformer

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

Electrons and holes

Protons and electrons

Holes and electrons

Electrons and protons

152. Identify the correct statement about minority carriers

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

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

153. Photovoltaic cell produces electrical energy from

Chemical energy

None of these

Light energy

Heat energy

154. The energy band gap is maximum in

Metals

Semiconductors

Superconductors

Insulators

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

p-type conductor

n-type semiconductor

n-type conductor

p-type semiconductor

156. 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

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

Base

Collector

Any of above

Emitter

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

None of these

Microsecond

Nanosecond

Millisecond

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

None of these

Stress

Strain

Force

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

In forward bias

In reverse bias

None of these

To A.C.

161. n-type semiconductor if formed

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

From pure Ge crystal

From pure Si crystal

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

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

None of these

Shear stress

Tensile stress

Compress ional stress

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

Remain fixed

Suddenly increases

Increases slowly

Decreases slowly

164. N-type crystal is

Positively charged

Negative charged

Neutral

None of these

165. The thickness of the base is equal to

Mean of thickness of emitter and collector

Thickness of collector

Thickness of emitter

Very small as compared to the thickness of emitter and collector

166. In a P-type semiconductor

Major current carriers are electrons

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

Major current carriers are mobile holes

Major current carriers are mobile negative ions

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

Crystal lattice

Unit cell

All of these

Ore

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

Arsenic

Antimony

Phosphorus

Aluminum

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

Holes

None of these

Neutrons

Electrons

170. The positive sign of gain indicates that

Input and out signals are in phase

Input and out signals are not in phase

None of these

May be in phase or not

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

Amplifier

Transistor

Rectifier

Diode

172. Polythene, potystrene and nylon are examples of

Glassy solids

Crystalline solids

Polymeric solids

Amorphous solids

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

Increase its life

Enable it to Telerate higher voltage

Increase its electrical conductivity

Increase its electrical resistivity

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

Insulators

Semiconductors

Conductors

Superconductors

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

Logic gates

Amplifier

Oscillator

Filter

176. Reverse bias applied on a junction diode

Raises the potential barrier

Increase the minority carrier current

Lowers the potential barrier

Increases the majority carrier current

177. When the output of OR gate is 1

If either input is zero

If either or both inputs are 1

Only if both inputs are 1

If both inputs are zero

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Maan AliLast Updated: April 19, 2025

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3 Comments

khansa noreen says:
September 11, 2020 at 10:12 pm

i want to know that how I prepare my entry test?
Name (required) says:
June 30, 2017 at 10:25 pm

assalam o alaikum mot of the answers are wrong…kindly check it
1. Humza arain says:
  January 7, 2021 at 4:27 pm
  
  Humza arain

ECAT Physics Electronics MCQS Online Test

Physics Electronics MCQS Online Test

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