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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.
Test Helpful For:	ECAT Entry Test Physics Online Test Interview Questions about Physics All Universities Entrance Test Recruitments Tests

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

1 mm

10¯⁶ cm

10¯¹² cm

1 cm

2. The forward resistance of the diode is

Many ohms

None of these

Few ohms

Ohms

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

Is independent of voltage

Decreased by reverse biasing

Increased by reverse biasing

Increased by forward biasing

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

Using a Coolidge tube

Suppressing half wave of A.C supply by using diode

Using a transistor

Suppressing the harmonics in A.C voltage

5. A transistor consists of

Three PN-junctions

Four PN-junctions

Two PN-junctions

One PN-junction

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

Narrow

Infinity

Zero

Wide

7. In a PN junction

P and N both are at same potential

High potential at N side and low potential at P side

High potential at P side and low potential at N side

Undetermined

8. The energy band gap is maximum in

Metals

Superconductors

Insulators

Semiconductors

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

Protons and electrons

Electrons and protons

Electrons and holes

Holes and electrons

10. The least doped region in a transistor is

Emitter

Base

Collector

11. Which one is reverse-biased?

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

Superconductor

Insulator

Semiconductor

None of these

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

P-type material

N-type material

Semiconductor

Super conductor

14. When the output of OR gate is 1

If either or both inputs are 1

If both inputs are zero

If either input is zero

Only if both inputs are 1

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

n-type conductor

p-type conductor

n-type semiconductor

p-type semiconductor

16. The energy band gap is maximum in

Metals

Superconductors

Insulators

Semiconductors

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

Zero

Almost zero

Infinity

None of these

18. To use a transistor as an amplifier

No bias voltages are required

Both junctions are forward biased

Both junctions are reverse biased

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

19. Identify the correct statement about minority carriers

Holes in n-type and p-type

Free electrons in n-type and p-type

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

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

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

Thousands

None of these

Man hundred

Hundreds

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

Hidden energy states

Forbidden energy states

Band levels

None of these

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

n-type

p-type

Extrinsic

Intrinsic

23. 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

None of these

Reversed biased

24. 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

25. In a P-type semiconductor

Major current carriers are mobile negative ions

Major current carriers are mobile holes

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

Major current carriers are electrons

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

Converter

An amplifier

Filtering circuit

A rectifier

27. In semiconductors at a room temperature

The valence band is completely filled

The conduction band is completely empty

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

28. 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

29. Which logic gate is represented by following diagram?

NOR

AND

EOR

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

Increases

Remains unchanged

Decreases and then increases

Decreases

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

Missing electrons

Protons

Neutrons

Extra electrons

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

Decreases

First A and B

Remains constant

Increases

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

None of these

N-type conductor

P-type semiconductor

N-type semiconductor

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

None of these

Capacitor is used

Solvent is used

Resistor is used

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

Very high

Almost negligible

Zero

Very low

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

Kilo ohms

Mega ohms

Ohms

Several mega ohms

37. Application of photodiode is/are

Detection of visible and invisible radiations

Logic gates

None of these

Automatic switching

38. 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

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

Potential is zero

Electric field is maximum

Electric field is zero

Potential is maximum

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

Ore

All of these

Crystal lattice

Unit cell

41. The critical temperature for mercury is

4.2 K

7.2 K

1.18 K

3.72 K

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

Each of them increases

Copper increases and germanium decreases

Each of them decreases

Copper decreases and germanium increases

43. Young’s modulus for copper is

None of these

70 x 10 Nm¯²

91 x 10 Nm¯²

110 Nm¯²

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

Resistance of copper decreases while that of germanium increases

Resistance of both increases

Resistance of copper increases while that of germanium decreases

Resistance of both decreases

45. An OP-AMPs can amplify

D.C.

A.C.

None of these

Both A.C. & D.C.

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

Strain

None of these

Force

Stress

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

Enable it to Telerate higher voltage

Increase its electrical conductivity

Increase its electrical resistivity

Increase its life

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

Holes

Neutrons

Electrons

Protons

49. Symbol represents

NOT gate

XNOR gate

NOR gate

NAND gate

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

Missing of electrons

Protons

Extra electrons

Neutrons

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

Virtual input

Output

Non-inverting voltage at output

Reference voltage on the other

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

Collector

Any of the above depending on nature of transistor

Base

Emitter

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

Forward bias

Temperature

Doping density

Diode design

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

Rectifier

Amplifier

P-type material

Oscillator

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

None of these

To A.C.

In reverse bias

In forward bias

56. Non-inverting amplifier circuits have

A very high input impedance

A very low input impedance

None of these

A low output impedance

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

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 low resistance to the current flow when forward biased

It has high resistance to the current flow when reverse biased

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

Phosphorus

Aluminum

Arsenic

Antimony

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

Low

Zero

High

None of these

60. In a semiconductor, the mobility of holes is

Equal to electrons

Greater than electrons

None

Less than electrons

61. 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

62. Radio waves of constant amplitude can be generated with

Oscillator

FET

Rectifier

Filter

63. NAND gate is

A basic gate

A universal gate

A basic universal gate

Not a universal gate

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

Emitter

Can be any of the above three

Base

Collector

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

Common collector configuration

None of these

Common base configuration

Common emitter configuration

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

Amplifier

Filter

Oscillator

Logic gates

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

Conductors

Insulators

Semiconductors

Superconductors

68. 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

Inverting terminal is at high potential

Both are at the same potential

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

At least one input is HIGH

All inputs are LOW

At least one input is LOW

All inputs are HIGH

70. Diode can work as

Modulator

Rectifier

Multivibrator

Oscillator

71. Acceptor and donor impurities donate

n-carriers only

p-carriers only

p-carriers and n-carriers respectively

n-carriers and p-carriers respectively

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

Drift of charges

Diffusion of charges

Both drift and diffusion of charges

Depends upon the nature of material

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

Collector

None of these

Base

Emitter

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

Neutrons

Electrons

None of these

Holes

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

Is independent of voltage

Decreased by reverse biasing

Increased by forward biasing

Increased by reverse biasing

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

Decreases

Decreases and then increases

Increases

Remains unchanged

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

0.9 V

0.5 V

0.7 V

0.67 V

78. Photodiode is used for

Detection of light

Emission of light

Light display

None of these

79. Arsenic, antimony or phosphorus are impurities of

n-type

None of these

p-type

may be p-type or n-type

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

Amplifier

Rectifier

Diode

Transistor

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

Amplification

Rectification

Magnification

All of these

82. The number of junctions in the PNP transistor are

83. Semi-conductor germanium and silicon are

Divalent

Pentavalent

Tetravalent

Trivalent

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

Tensile stress

Compress ional stress

Shear stress

None of these

85. 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

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

The conduction band is completely empty

86. The least doped region in a transistor is

Emitter

Either emitter or collector

Collector

Base

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

Young’s modulus

Shear modulus

Bulk modulus

None of these

88. 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

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

None of these

Rectifier

Detector

Oscillator

90. LDR means:

None of these

Low degree resistor

Light dependent resistance

Low degree radiations

91. 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

Diode is neutralized

None of these

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

Extra electrons

Neutrons

Protons

Missing electrons

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

Each of them decreases

Copper decreases and germanium increases

Each of them increases

Copper increases and germanium decreases

94. A substance which have empty conduction band is called

Insulator

Semiconductor

None of these

Conductor

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

9.8

4.9

96. Depletion region of a junction is formed

Under forward bias

During the manufacturing process

When temperature varies

Under reverse bias

97. In forward bias the width of potential barrier

No effect

Decreases

Remains same

Increases

98. In half wave rectification

Current flows in pulses

Current flows in one directions

Only half cycle is used

None of these

99. 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

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

n-type semiconductor

p-type conductor

p-type semiconductor

n-type conductor

101. Which one is forward bias?

102. Zener breakdown in a semiconductor diode occurs when

Forward current exceeds certain value

Forward bias exceeds certain value

Potential barrier is reduced to zero

Reverse bias exceeds certain value

103. A diode as a rectifier converts:

D.C. into A.C.

Low voltage to high voltage

A.C. into D.C.

High voltage to low voltage

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

Modulus of electricity

None of these

Young’s modulus

Bulk’s modulus

105. Light emitting diode work when it is

Forward biases

Reverse biased

None of these

Both

106. 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

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

Increase the minority carrier current

Lowers the potential barrier

Increase the majority carrier current

Raises the potential barrier

108. N-type crystal is

None of these

Positively charged

Neutral

Negative charged

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

x-rays

Gamma Rays

Electromagnetic Waves

Transverse Waves

110. In a n-p-n transistor:

Holes move from emitter to base

Negative charge moves from collector to base

Negative charge moves from emitter to base

Holes move from base to collector

111. In Germanium crystal, impurity donor elements have valiancy

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

The photo diodes

Solar cells

The light emitting diode

The switch

113. The thickness of the base is equal to

Thickness of collector

Mean of thickness of emitter and collector

Very small as compared to the thickness of emitter and collector

Thickness of emitter

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

Semiconductor

Alloy

Insulator

Conductor

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

Off switch

Inductor

Capacitor

On switch

116. Depletion layer consists of

Immobile ions

Mobile ions

Electrons

Protons

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

Boron

Aluminum

All of these

Gallium

118. When n-type of semiconductor is heated,

Number of electrons increases while that of holes decreases

Number of electrons and holes increases equally

Number of electrons and holes remains same

Number of holes increases while that of holes decreases

119. In p-type semiconductor

The number of mobile holes exceeds the number of acceptors

Major carrier is mobile holes

Major carrier is mobile negative ions

Major current carrier is electrons

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

Aluminum

All of above

Boron

Gallium

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

Emitter

Collector

Can be any of the above three

Base

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

123. Reverse bias applied on a junction diode

Increase the minority carrier current

Lowers the potential barrier

Increases the majority carrier current

Raises the potential barrier

124. Transistor can be used as

Full wave rectifier

Amplifier

Half wave rectifier

Filter

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

4.9

9.8

126. When NPN transistor is used as an amplifier

Electrons move from base to emitter

Electrons move from emitter to base

Electrons move from collector to base

Holes move from base to emitter

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

Require more current

Damaged

Works efficiently

None of these

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

Insulator

p-type

Superconductor

n-type

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

OR gates

NOT gates

AND gates

NAND gates

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

None of these

Millisecond

Microsecond

Nanosecond

131. 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

132. At absolute zero, Si acts as

Non-metal

Metal

None of these

Insulator

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

AND gate

NAND gate

NOT gate

OR gate

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

OR gate

XOR gate

NOT gate

AND gate

135. n-type semiconductor if formed

From pure Si crystal

From pure Ge 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

136. 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 free electrons and few holes

Large number of holes and few electrons

137. In the transistor schematic symbol, the arrow

Point from north to south

Is locate on the collector

Is located on the base

Is located on the emitter

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

Aluminum

Phosphorus

Antimony

Arsenic

139. 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

140. The working of transistor as amplifier is similar to

Step up transformer

Triode vacuum tube

Three diodes in common

Step down transformer

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

Antimony

Arsenic

Indium

Phosphorus

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

Suddenly increases

Remain fixed

Increases slowly

Decreases slowly

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

NOT gate

AND gate

NOR gate

OR gate

144. 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 open loop gain all of above

It offers a very low output resistance

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

Comparator

OR gate

INVERTER gate

AND gate

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

Large number of holes and electrons

Large number of free electrons and few holes

Large number of holes and few electrons

Equal number of free electrons and holes

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

Majority carriers

Dual carriers

Blockers

Minority carriers

148. The ratio β shows the

Voltage gain

Input resistance

Current gain

None of these

149. Which is normal used of transistor?

Rectifier

Diode

P-type material

Switching device

150. The ratio β represents

151. 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

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

None of these

Depletion region

Diffusion region

Charged region

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

Zero amplitude

Variable amplitude

Unit amplitude

Constant amplitude

154. In Germanium crystal, impurity donor elements have valiancy

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

AND gates and NOT gates

Or gates and NOT gates

OR gates only

AND gates, OR gates, and NOT gates

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

Enable it to Telerate higher voltage

Increase its life

Increases its electrical conductivity

Increase its electrical resistivity

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

Extrinsic

n-type

Intrinsic

p-type

158. A NAND gate has:

LOW inputs and a LOW output

HIGH inputs and a HIGH output

None of these

LOW inputs and a HIGH output

159. Reverse bias applied on a junction diode

Lowers the potential barrier

Increases the majority carrier current

Raises the potential barrier

Increase the minority carrier current

160. In insulators

Valence band is partially filled with electrons

Conduction band is filled with electrons and valence bad is empty

Conduction band is partially filled with electrons

Conduction band is empty and valence band is filled with electrons

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

Boron

Gold

Phosphorus

Aluminum

162. Photovoltaic cell produces electrical energy from

Heat energy

None of these

Light energy

Chemical energy

163. 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 remains unchanged

Potential barrier in depletion layer increases

Diode is reverse biased

Diode is forward based

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

Computers

Transformers

Electric generations

Electric motors

165. Polythene, potystrene and nylon are examples of

Polymeric solids

Glassy solids

Crystalline solids

Amorphous solids

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

Stress

Force

Strain

None of these

167. At absolute zero, Si acts as

Non-metal

Metal

None of these

Insulator

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

Less than one

Greater than one

Of zero

Equal to one

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

Amplifier

Filter

Logic gates

Oscillator

170. The operation of a transistor requires

That the base be heated

That the collector be heated

That the emitter be heated

None of these

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

Tightly bound electrons

None of these

Valence electrons

Free electrons

172. A diode as a rectifier converts:

Low voltage to high voltage

D.C. into A.C.

High voltage to low voltage

A.C. into D.C.

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

Equal to emitter current

Any of above

Slightly less than emitter current

Greater than emitter current

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

mix

any of above

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

Base

Collector

Emitter

Any of above

176. In insulators

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

Conduction band is filled with electrons and valence band is empty

177. A n-p-n transistor conducts when

Both collector and emitter are negative with respect to the base

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

Both collector and emitter are positive with respect to the base

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

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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

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