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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. Young’s modulus for copper is

70 x 10 Nm¯²

91 x 10 Nm¯²

110 Nm¯²

None of these

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

Each of them increases

Each of them decreases

Copper decreases and germanium increases

Copper increases and germanium decreases

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

180° Phase shift

90° Phase shift

No Phase shift

120° Phase shift

4. 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

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

Large number of holes and few electrons

Large number of holes and electrons

Large number of free electrons and few holes

Equal number of free electrons and holes

6. The energy band gap is maximum in

Semiconductors

Metals

Superconductors

Insulators

7. 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

8. Which one is reverse-biased?

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

None of these

Common emitter configuration

Common collector configuration

Common base configuration

10. Photodiode is used for

Detection of light

None of these

Emission of light

Light display

11. Reverse bias applied on a junction diode

Lowers the potential barrier

Increase the minority carrier current

Raises the potential barrier

Increases the majority carrier current

12. At absolute zero, Si acts as

Insulator

None of these

Non-metal

Metal

13. In half wave rectification

Current flows in one directions

Only half cycle is used

Current flows in pulses

None of these

14. The forward resistance of the diode is

Few ohms

Ohms

Many ohms

None of these

15. The critical temperature for mercury is

3.72 K

4.2 K

7.2 K

1.18 K

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

Semiconductors

Insulators

Conductors

Superconductors

17. 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

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

AND gate

Comparator

INVERTER gate

OR gate

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

Stress

Strain

None of these

Force

20. Photovoltaic cell produces electrical energy from

Heat energy

None of these

Chemical energy

Light energy

21. 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

22. The working of transistor as amplifier is similar to

Step down transformer

Step up transformer

Triode vacuum tube

Three diodes in common

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

Hundreds

Man hundred

Thousands

None of these

24. 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

Increase its electrical conductivity

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

10¯⁶ cm

1 mm

10¯¹² cm

1 cm

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

The light emitting diode

The photo diodes

Solar cells

The switch

27. 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

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

Filter

Amplifier

Logic gates

Oscillator

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

Diode

Amplifier

Rectifier

Transistor

30. A piece 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

31. Arsenic, antimony or phosphorus are impurities of

n-type

p-type

None of these

may be p-type or n-type

32. 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

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

Crystal lattice

Unit cell

All of these

Ore

34. 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

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

x-rays

Transverse Waves

Gamma Rays

Electromagnetic Waves

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

Narrow

Wide

Infinity

Zero

37. 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

38. The ratio β represents

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

Base

Collector

Emitter

Can be any of the above three

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

Using a Coolidge tube

Using a transistor

Suppressing the harmonics in A.C voltage

Suppressing half wave of A.C supply by using diode

41. The operation of a transistor requires

That the base be heated

None of these

That the emitter be heated

That the collector be heated

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

NOR gate

NOT gate

OR gate

AND gate

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

Equal to emitter current

Greater than emitter current

Any of above

Slightly less than emitter current

44. In a PN junction

High potential at N side and low potential at P side

P and N both are at same potential

Undetermined

High potential at P side and low potential at N side

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

N-type semiconductor

None of these

N-type conductor

P-type semiconductor

46. Which is normal used of transistor?

Rectifier

Diode

P-type material

Switching device

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

Holes and electrons

Protons and electrons

Electrons and protons

Electrons and holes

48. N-type crystal is

Neutral

Negative charged

Positively charged

None of these

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

Increased by forward biasing

Is independent of voltage

Increased by reverse biasing

Decreased by reverse biasing

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

Resistance of copper decreases while that of germanium increases

Resistance of copper increases while that of germanium decreases

Resistance of both increases

Resistance of both decreases

51. Identify the correct statement about minority carriers

Holes in n-type and p-type

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

Free electrons in n-type and p-type

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

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

It has high resistance to the current flow when reverse biased

Its conductivity increases with rise of temperature

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

53. 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

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

Holes

Neutrons

Protons

Electrons

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

Neutrons

Extra electrons

Missing electrons

Protons

56. When n-type of semiconductor is heated,

Number of electrons and holes remains same

Number of holes increases while that of holes decreases

Number of electrons increases while that of holes decreases

Number of electrons and holes increases equally

57. 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

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

Neutrons

Missing electrons

Extra electrons

Protons

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

n-type semiconductor

p-type conductor

p-type semiconductor

n-type conductor

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

AND gates, OR gates, and NOT gates

AND gates and NOT gates

OR gates only

Or gates and NOT gates

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

Almost zero

Zero

None of these

Infinity

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

None of these

Low

Zero

High

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

Greater than one

Less than one

Equal to one

Of zero

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

None of these

Require more current

Works efficiently

Damaged

65. An OP-AMPs can amplify

D.C.

A.C.

Both A.C. & D.C.

None of these

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

In reverse bias

To A.C.

In forward bias

None of these

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

Arsenic

Antimony

Phosphorus

Aluminum

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. n-type semiconductor if formed

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

From pure Ge crystal

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

From pure Si crystal

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 number of junctions in the PNP transistor are

72. 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 increases

Potential barrier in depletion layer remains unchanged

Diode is forward based

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

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

Collector

Base

Any of the above depending on nature of transistor

Emitter

75. In forward bias the width of potential barrier

Decreases

No effect

Remains same

Increases

76. 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

Holes move from emitter be base

77. NAND gate is

A basic gate

A universal gate

Not a universal gate

A basic universal gate

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

Oscillator

Rectifier

Detector

None of these

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

Converter

Filtering circuit

A rectifier

An amplifier

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

Forward bias

Doping density

Diode design

Temperature

81. Radio waves of constant amplitude can be generated with

FET

Rectifier

Filter

Oscillator

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

Oscillator

Rectifier

Amplifier

P-type material

83. The least doped region in a transistor is

Base

Emitter

Collector

Either emitter or collector

84. 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

85. 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

86. 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 forward biased

Diode is reverse biased

None of these

Diode is neutralized

87. LDR means:

Light dependent resistance

None of these

Low degree resistor

Low degree radiations

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

p-type semiconductor

n-type conductor

n-type semiconductor

p-type conductor

89. The least doped region in a transistor is

Collector

Emitter

Base

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

Dual carriers

Minority carriers

Blockers

Majority carriers

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

Antimony

Arsenic

Indium

Phosphorus

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

Increases slowly

Suddenly increases

Decreases slowly

Remain fixed

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

Emitter

Base

Can be any of the above three

Collector

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

None of these

Strain

Force

Stress

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

p-type

Extrinsic

Intrinsic

n-type

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

All of above

Boron

Gallium

Aluminum

97. 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):

NAND

AND

NOR

98. Which logic gate is represented by following diagram?

AND

NOR

EOR

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

p-type

Insulator

Superconductor

n-type

100. In the transistor schematic symbol, the arrow

Is located on the base

Is locate on the collector

Point from north to south

Is located on the emitter

101. Polythene, potystrene and nylon are examples of

Polymeric solids

Amorphous solids

Glassy solids

Crystalline solids

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

Depletion region

Diffusion region

None of these

Charged region

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

Emitter

None of these

Base

Collector

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

Non-inverting voltage at output

Output

Reference voltage on the other

Virtual input

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

NAND gates

NOT gates

OR gates

AND gates

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

Band levels

None of these

Forbidden energy states

Hidden energy states

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

Collector

Base

Emitter

Any of above

108. Acceptor and donor impurities donate

n-carriers and p-carriers respectively

p-carriers and n-carriers respectively

n-carriers only

p-carriers only

109. Reverse bias applied on a junction diode

Raises the potential barrier

Lowers the potential barrier

Increase the minority carrier current

Increases the majority carrier current

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

n-type

p-type

Extrinsic

Intrinsic

111. Depletion region of a junction is formed

During the manufacturing process

Under forward bias

Under reverse bias

When temperature varies

112. Diode can work as

Modulator

Multivibrator

Rectifier

Oscillator

113. When NPN transistor is used as an amplifier

Electrons move from base to emitter

Holes move from base to emitter

Electrons move from collector to base

Electrons move from emitter to base

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

Phosphorus

Aluminum

Arsenic

Antimony

115. In p-type semiconductor

Major carrier is mobile holes

Major carrier is mobile negative ions

The number of mobile holes exceeds the number of acceptors

Major current carrier is electrons

116. In a semiconductor, the mobility of holes is

Equal to electrons

Greater than electrons

Less than electrons

None

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

any of above

mix

118. Transistor can be used as

Half wave rectifier

Amplifier

Full wave rectifier

Filter

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

Constant amplitude

Unit amplitude

Variable amplitude

Zero amplitude

120. 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

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

Electric generations

Transformers

Electric motors

Computers

122. In Germanium crystal, impurity donor elements have valiancy

123. A transistor consists of

Three PN-junctions

Four PN-junctions

Two PN-junctions

One PN-junction

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

Electric field is zero

Potential is maximum

Electric field is maximum

Potential is zero

125. In a P-type semiconductor

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

Major current carriers are electrons

Major current carriers are mobile negative ions

Major current carriers are mobile holes

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

OR gate

NOT gate

AND gate

NAND gate

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

4.9

9.8

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

Aluminum

Gallium

All of these

Boron

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

None of these

Bulk modulus

Young’s modulus

Shear modulus

130. Semi-conductor germanium and silicon are

Tetravalent

Trivalent

Divalent

Pentavalent

131. 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

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

Electric field is maximum

Electric field is zero

Potential is zero

Potential is maximum

133. When the output of OR gate is 1

If both inputs are zero

If either or both inputs are 1

Only if both inputs are 1

If either input is zero

134. In insulators

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 band is empty

Valence band is partially filled with electrons

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

4.9

9.8

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

OR gate

NOT gate

AND gate

XOR gate

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

Millisecond

Microsecond

Nanosecond

None of these

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

Off switch

On switch

Inductor

Capacitor

139. A NAND gate has:

LOW inputs and a LOW output

HIGH inputs and a HIGH output

LOW inputs and a HIGH output

None of these

140. Symbol represents

NOT gate

NAND gate

NOR gate

XNOR gate

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

None of these

Compress ional stress

Tensile stress

Shear stress

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

Kilo ohms

Ohms

Mega ohms

Several mega ohms

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

Decreases and then increases

Increases

Decreases

Remains unchanged

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

Boron

Gold

Aluminum

Phosphorus

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

Oscillator

Logic gates

Filter

Amplifier

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

Missing of electrons

Protons

Extra electrons

Neutrons

147. Non-inverting amplifier circuits have

None of these

A very low input impedance

A low output impedance

A very high input impedance

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

0.7 V

0.5 V

0.9 V

0.67 V

149. A substance which have empty conduction band is called

Conductor

None of these

Semiconductor

Insulator

150. 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

151. The ratio β shows the

Voltage gain

Input resistance

Current gain

None of these

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

Tightly bound electrons

None of these

Free electrons

Valence electrons

153. 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

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

Increases

Remains unchanged

Decreases

Decreases and then increases

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

Conductor

Insulator

Semiconductor

Alloy

156. Application of photodiode is/are

None of these

Logic gates

Detection of visible and invisible radiations

Automatic switching

157. The energy band gap is maximum in

Insulators

Semiconductors

Superconductors

Metals

158. 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

159. With negative feedback, the returning signal:

Aids the input signal

Opposes the input signal

Is proportional to differential voltage gain

Is proportional to output current

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

Decreases

Increases

Remains constant

First A and B

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

Almost negligible

Zero

Very high

Very low

162. Which one is forward bias?

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

P-type material

Semiconductor

N-type material

Super conductor

164. Depletion layer consists of

Protons

Mobile ions

Electrons

Immobile ions

165. The thickness of the base is equal to

Thickness of collector

Thickness of emitter

Mean of thickness of emitter and collector

Very small as compared to the thickness of emitter and collector

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

Semiconductor

Insulator

Superconductor

None of these

167. Light emitting diode work when it is

Forward biases

Both

Reverse biased

None of these

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

Increases its electrical conductivity

Increase its life

Enable it to Telerate higher voltage

Increase its electrical resistivity

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

Amplification

Magnification

All of these

Rectification

170. In Germanium crystal, impurity donor elements have valiancy

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

Holes

Electrons

Neutrons

None of these

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

Modulus of electricity

None of these

Young’s modulus

Bulk’s modulus

173. 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

Zero biased

None of these

Reversed biased

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

Lowers the potential barrier

Raises the potential barrier

Increase the majority carrier current

Increase the minority carrier current

175. 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 output resistance

None of these

It offers a very low open loop gain all of above

176. A diode as a rectifier converts:

A.C. into D.C.

Low voltage to high voltage

High voltage to low voltage

D.C. into A.C.

177. At absolute zero, Si acts as

Insulator

Metal

Non-metal

None of these

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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

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