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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. Acceptor and donor impurities donate

p-carriers only

n-carriers and p-carriers respectively

p-carriers and n-carriers respectively

n-carriers only

2. 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

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

p-type

Intrinsic

n-type

Extrinsic

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

Microsecond

None of these

Millisecond

Nanosecond

5. 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

6. In a semiconductor, the mobility of holes is

None

Equal to electrons

Greater than electrons

Less than electrons

7. Reverse bias applied on a junction diode

Lowers the potential barrier

Raises the potential barrier

Increases the majority carrier current

Increase the minority carrier current

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

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

Electrons and holes

Electrons and protons

Protons and electrons

Holes and electrons

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

Less than one

Of zero

Equal to one

Greater than one

11. N-type crystal is

None of these

Negative charged

Neutral

Positively charged

12. LDR means:

Low degree radiations

Light dependent resistance

Low degree resistor

None of these

13. Transistor can be used as

Half wave rectifier

Filter

Amplifier

Full wave rectifier

14. Application of photodiode is/are

Detection of visible and invisible radiations

None of these

Automatic switching

Logic gates

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

Electromagnetic Waves

Gamma Rays

Transverse Waves

x-rays

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

Bulk’s modulus

Young’s modulus

None of these

Modulus of electricity

17. Depletion layer consists of

Electrons

Immobile ions

Mobile ions

Protons

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

Decreases slowly

Remain fixed

Increases slowly

Suddenly increases

19. Arsenic, antimony or phosphorus are impurities of

n-type

may be p-type or n-type

None of these

p-type

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

Comparator

INVERTER gate

AND gate

OR gate

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

P-type semiconductor

N-type conductor

N-type semiconductor

None of these

22. In the transistor schematic symbol, the arrow

Point from north to south

Is located on the emitter

Is located on the base

Is locate on the collector

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

Copper decreases and germanium increases

Each of them increases

Copper increases and germanium decreases

Each of them decreases

24. A substance which have empty conduction band is called

Conductor

None of these

Insulator

Semiconductor

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

It offers a very low open loop gain all of above

None of these

It offers a very high inputs resistance to the input current

It offers a very low output resistance

26. At absolute zero, Si acts as

Non-metal

Insulator

None of these

Metal

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

Constant amplitude

Zero amplitude

Variable amplitude

Unit amplitude

28. 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

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

Increases

Remains unchanged

Decreases and then increases

Decreases

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

Conductor

Insulator

Semiconductor

Alloy

31. In forward bias the width of potential barrier

Increases

Decreases

No effect

Remains same

32. n-type semiconductor if formed

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

From pure Ge crystal

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

From pure Si crystal

33. 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

34. In a P-type semiconductor

Major current carriers are mobile holes

Major current carriers are mobile negative ions

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

Major current carriers are electrons

35. 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

Increase its life

Increase its electrical conductivity

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

Amplification

Rectification

Magnification

All of these

37. To use a transistor as an amplifier

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

Both junctions are reverse biased

No bias voltages are required

Both junctions are forward biased

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

Oscillator

None of these

Rectifier

Detector

39. The least doped region in a transistor is

Base

Emitter

Collector

40. When NPN transistor is used as an amplifier

Holes move from base to emitter

Electrons move from base to emitter

Electrons move from emitter to base

Electrons move from collector to base

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

Aluminum

Boron

All of these

Gallium

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

Protons

Electrons

Neutrons

Holes

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

Strain

None of these

Force

Stress

44. Diode can work as

Oscillator

Rectifier

Multivibrator

Modulator

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

Increases its electrical conductivity

Increase its life

Increase its electrical resistivity

Enable it to Telerate higher voltage

46. Which logic gate is represented by following diagram?

EOR

NOR

AND

47. The working of transistor as amplifier is similar to

Three diodes in common

Triode vacuum tube

Step down transformer

Step up transformer

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

NAND gate

OR gate

NOT gate

AND gate

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

Amplifier

Filter

Logic gates

Oscillator

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

9.8

4.9

51. 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

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

Electrons move from base to collector

Holes move from base to emitter

Holes move from emitter be base

Holes move from emitter to base

53. In insulators

Conduction band is empty and valence band is filled with electrons

Valence band is partially filled with electrons

Conduction band is filled with electrons and valence band is empty

Conduction band is partially filled with electrons

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

Amplifier

Logic gates

Filter

Oscillator

55. With negative feedback, the returning signal:

Is proportional to differential voltage gain

Opposes the input signal

Aids the input signal

Is proportional to output current

56. Zener breakdown in a semiconductor diode occurs when

Forward bias exceeds certain value

Reverse bias exceeds certain value

Potential barrier is reduced to zero

Forward current exceeds certain value

57. Which is normal used of transistor?

Switching device

Rectifier

P-type material

Diode

58. A diode as a rectifier converts:

Low voltage to high voltage

High voltage to low voltage

A.C. into D.C.

D.C. into A.C.

59. Which one is reverse-biased?

60. 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

61. 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

62. 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

63. When n-type of semiconductor is heated,

Number of electrons and holes remains same

Number of electrons increases while that of holes decreases

Number of electrons and holes increases equally

Number of holes increases while that of holes decreases

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

Boron

Phosphorus

Aluminum

Gold

65. 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

66. 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

67. Photovoltaic cell produces electrical energy from

Heat energy

None of these

Chemical energy

Light energy

68. In p-type semiconductor

Major current carrier is electrons

The number of mobile holes exceeds the number of acceptors

Major carrier is mobile negative ions

Major carrier is mobile holes

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

N-type material

P-type material

Super conductor

Semiconductor

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

Diffusion region

Charged region

Depletion region

None of these

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

It has high resistance to the current flow when reverse biased

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

Its conductivity increases with rise of temperature

It has low resistance to the current flow when forward biased

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

Solar cells

The light emitting diode

The photo diodes

The switch

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

0.9 V

0.7 V

0.67 V

0.5 V

74. The positive sign of gain indicates that

May be in phase or not

Input and out signals are not in phase

None of these

Input and out signals are in phase

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

Off switch

Inductor

On switch

Capacitor

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

Aluminum

Gallium

Boron

All of above

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

Aluminum

Arsenic

Phosphorus

Antimony

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

None of these

Band levels

Hidden energy states

Forbidden energy states

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

Missing electrons

Extra electrons

Protons

Neutrons

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

Potential is maximum

Electric field is maximum

Electric field is zero

Potential is zero

81. 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

None of these

Diode is neutralized

Diode is forward biased

82. 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 increases

Each of them decreases

Copper decreases and germanium increases

83. Polythene, potystrene and nylon are examples of

Amorphous solids

Crystalline solids

Polymeric solids

Glassy solids

84. The ratio β shows the

Current gain

None of these

Voltage gain

Input resistance

85. At absolute zero, Si acts as

None of these

Metal

Insulator

Non-metal

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

10¯⁶ cm

10¯¹² cm

1 cm

1 mm

87. The energy band gap is maximum in

Superconductors

Metals

Insulators

Semiconductors

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

Rectifier

Transistor

Amplifier

Diode

89. When the output of OR gate is 1

Only if both inputs are 1

If either input is zero

If either or both inputs are 1

If both inputs are zero

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

Protons

Extra electrons

Missing electrons

Neutrons

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

Neutrons

Missing of electrons

Extra electrons

Protons

92. Identify the correct statement about minority carriers

Free electrons in n-type and p-type

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

Holes in n-type and p-type

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

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

Superconductors

Insulators

Semiconductors

Conductors

94. In half wave rectification

Current flows in pulses

Current flows in one directions

Only half cycle is used

None of these

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

None of these

Valence electrons

Tightly bound electrons

Free electrons

96. Photodiode is used for

Emission of light

Light display

Detection of light

None of these

97. The operation of a transistor requires

None of these

That the base be heated

That the emitter be heated

That the collector be heated

98. In semiconductors at a room temperature

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

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

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

In reverse bias

To A.C.

In forward bias

None of these

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

Infinity

Almost zero

None of these

Zero

101. 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

Depends upon the nature of material

Diffusion of charges

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

Decreases and then increases

Increases

Remains unchanged

Decreases

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

Compress ional stress

Tensile stress

Shear stress

None of these

104. The ratio β represents

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

p-type

Extrinsic

Intrinsic

n-type

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

4.9

9.8

107. The critical temperature for mercury is

4.2 K

1.18 K

3.72 K

7.2 K

108. 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

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

Emitter

Collector

Base

Can be any of the above three

110. Symbol represents

NOT gate

NAND gate

NOR gate

XNOR gate

111. A NAND gate has:

LOW inputs and a HIGH output

HIGH inputs and a HIGH output

None of these

LOW inputs and a LOW output

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

Superconductor

Insulator

None of these

Semiconductor

113. In insulators

Conduction band is empty and valence band is filled with electrons

Conduction band is filled with electrons and valence bad is empty

Valence band is partially filled with electrons

Conduction band is partially filled with electrons

114. 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

115. The forward resistance of the diode is

Ohms

Few ohms

None of these

Many ohms

116. In a PN junction

P and N both are at same potential

High potential at P side and low potential at N side

Undetermined

High potential at N side and low potential at P side

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

Rectifier

P-type material

Oscillator

Amplifier

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

Very low

Almost negligible

Zero

Very high

119. Non-inverting amplifier circuits have

A very low input impedance

A low output impedance

A very high input impedance

None of these

120. Young’s modulus for copper is

110 Nm¯²

70 x 10 Nm¯²

91 x 10 Nm¯²

None of these

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

n-type semiconductor

n-type conductor

p-type semiconductor

p-type conductor

122. Light emitting diode work when it is

Both

Reverse biased

Forward biases

None of these

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

Lowers the potential barrier

Raises the potential barrier

Increase the minority carrier current

Increase the majority carrier current

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

At least one input is HIGH

At least one input is LOW

All inputs are LOW

All inputs are HIGH

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

Non-inverting voltage at output

Virtual input

Reference voltage on the other

Output

126. 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

120° Phase shift

180° Phase shift

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

Electric motors

Electric generations

Transformers

Computers

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

Dual carriers

Blockers

Majority carriers

Minority carriers

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

Both are at the same potential

Non-inverting terminal is at high potential

Both are at the high potential

Inverting terminal is at high potential

130. An OP-AMPs can amplify

A.C.

None of these

D.C.

Both A.C. & D.C.

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

Strain

Stress

None of these

Force

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

p-type semiconductor

n-type conductor

n-type semiconductor

p-type conductor

133. 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.

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

Crystal lattice

Unit cell

Ore

All of these

135. In Germanium crystal, impurity donor elements have valiancy

136. A transistor consists of

Four PN-junctions

One PN-junction

Two PN-junctions

Three PN-junctions

137. 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

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

None of these

Young’s modulus

Shear modulus

Bulk modulus

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

Ohms

Kilo ohms

Mega ohms

Several mega ohms

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

Large number of holes and few electrons

Equal number of free electrons and holes

Large number of holes and electrons

Large number of free electrons and few holes

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

Wide

Narrow

Infinity

Zero

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

Slightly less than emitter current

Equal to emitter current

Any of above

Greater than emitter current

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

Forward bias

Temperature

Diode design

Doping density

144. 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

145. The energy band gap is maximum in

Superconductors

Metals

Semiconductors

Insulators

146. 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

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

any of above

mix

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

Common collector configuration

Common base configuration

Common emitter configuration

None of these

149. Which one is forward bias?

150. The least doped region in a transistor is

Emitter

Base

Either emitter or collector

Collector

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

Emitter

Collector

Base

Any of above

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

Phosphorus

Arsenic

Aluminum

Antimony

153. 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

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

p-type

Insulator

n-type

Superconductor

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

An amplifier

Filtering circuit

Converter

A rectifier

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

Large number of free electrons and few holes

Large number of holes and few electrons

Large number of holes and electrons

Equal number of free electrons and holes

157. Semi-conductor germanium and silicon are

Tetravalent

Trivalent

Pentavalent

Divalent

158. Radio waves of constant amplitude can be generated with

FET

Filter

Oscillator

Rectifier

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

Arsenic

Phosphorus

Antimony

Indium

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

Collector

None of these

Base

Emitter

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

Damaged

None of these

Works efficiently

Require more current

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

None of these

Solvent is used

Capacitor is used

Resistor is used

163. 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

164. 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

Diode is reverse biased

Diode is forward based

Potential barrier in depletion layer increases

165. 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 conduction band is completely empty

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

166. In Germanium crystal, impurity donor elements have valiancy

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

Thousands

Hundreds

Man hundred

None of these

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

NOT gate

OR gate

AND gate

XOR gate

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

Remains constant

Increases

First A and B

Decreases

170. Depletion region of a junction is formed

During the manufacturing process

Under forward bias

Under reverse bias

When temperature varies

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

AND gates

NOT gates

OR gates

NAND gates

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

None of these

High

Zero

Low

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

OR gates only

Or gates and NOT gates

AND gates, OR gates, and NOT gates

AND gates and NOT gates

174. The thickness of the base is equal to

Mean of thickness of emitter and collector

Very small as compared to the thickness of emitter and collector

Thickness of emitter

Thickness of collector

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

None of these

Neutrons

Holes

Electrons

176. NAND gate is

A basic universal gate

A universal gate

Not a universal gate

A basic gate

177. The number of junctions in the PNP transistor are

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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

ECAT Physics Electronics Chapter Online Test

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