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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. 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 forward biased

None of these

Diode is reverse biased

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

Zero amplitude

Variable amplitude

Constant amplitude

Unit amplitude

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

Capacitor is used

Resistor is used

Solvent is used

None of these

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

1 cm

1 mm

10¯⁶ cm

10¯¹² cm

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

Free electrons

Valence electrons

Tightly bound electrons

None of these

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

Holes move from base to emitter

Holes move from emitter to base

Electrons move from base to collector

7. At absolute zero, Si acts as

Metal

Non-metal

Insulator

None of these

8. Zener breakdown in a semiconductor diode occurs when

Forward current exceeds certain value

Forward bias exceeds certain value

Reverse bias exceeds certain value

Potential barrier is reduced to zero

9. In a semiconductor, the mobility of holes is

None

Greater than electrons

Less than electrons

Equal to electrons

10. 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

11. A substance which have empty conduction band is called

Insulator

None of these

Semiconductor

Conductor

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

0.9 V

0.7 V

0.5 V

0.67 V

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

Superconductors

Insulators

Conductors

Semiconductors

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

Thousands

None of these

Man hundred

Hundreds

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

Suddenly increases

Remain fixed

Decreases slowly

Increases slowly

16. 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

17. In a PN junction

Undetermined

High potential at P side and low potential at N side

P and N both are at same potential

High potential at N side and low potential at P side

18. In insulators

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

Valence band is partially filled with electrons

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

Magnification

All of these

Rectification

Amplification

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

Base

Can be any of the above three

Emitter

Collector

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

Phosphorus

Indium

Antimony

Arsenic

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

4.9

9.8

23. The energy band gap is maximum in

Insulators

Semiconductors

Superconductors

Metals

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

Rectifier

Transistor

Amplifier

Diode

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

The photo diodes

Solar cells

The light emitting diode

The switch

26. Which is normal used of transistor?

Diode

Rectifier

P-type material

Switching device

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

Super conductor

Semiconductor

P-type material

N-type material

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

INVERTER gate

AND gate

OR gate

Comparator

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

p-type conductor

n-type conductor

n-type semiconductor

p-type semiconductor

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

No Phase shift

180° Phase shift

120° Phase shift

90° Phase shift

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

Suppressing the harmonics in A.C voltage

Using a transistor

Suppressing half wave of A.C supply by using diode

Using a Coolidge tube

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

Both are at the high potential

Both are at the same potential

Non-inverting terminal is at high potential

Inverting terminal is at high potential

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

Electrons

Neutrons

None of these

Holes

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

Missing electrons

Protons

Neutrons

Extra electrons

35. The critical temperature for mercury is

7.2 K

1.18 K

4.2 K

3.72 K

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

Protons and electrons

Electrons and holes

Electrons and protons

Holes and electrons

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

Antimony

Aluminum

Arsenic

Phosphorus

38. 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

39. The ratio β shows the

Input resistance

Current gain

None of these

Voltage gain

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

None of these

Common collector configuration

Common emitter configuration

Common base configuration

41. At absolute zero, Si acts as

None of these

Non-metal

Insulator

Metal

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

Is independent of voltage

Increased by forward biasing

Decreased by reverse biasing

Increased by reverse biasing

43. When NPN transistor is used as an amplifier

Electrons move from emitter to base

Holes move from base to emitter

Electrons move from collector to base

Electrons move from base to emitter

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

None of these

Bulk’s modulus

Young’s modulus

Modulus of electricity

45. The least doped region in a transistor is

Emitter

Collector

Either emitter or collector

Base

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

Aluminum

Gold

Boron

Phosphorus

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

Zero

Infinity

Narrow

Wide

48. 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

NOT gate

AND gate

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

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

Potential is zero

Potential is maximum

Electric field is zero

Electric field is maximum

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

Shear modulus

Young’s modulus

Bulk modulus

None of these

52. 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

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

Off switch

On switch

Inductor

Capacitor

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

None of these

It offers a very low open loop gain all of above

It offers a very low output resistance

It offers a very high inputs resistance to the input current

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

At least one input is LOW

All inputs are HIGH

At least one input is HIGH

All inputs are LOW

56. Acceptor and donor impurities donate

n-carriers and p-carriers respectively

n-carriers only

p-carriers only

p-carriers and n-carriers respectively

57. Non-inverting amplifier circuits have

A very low input impedance

A very high input impedance

None of these

A low output impedance

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

An amplifier

Converter

A rectifier

Filtering circuit

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

OR gates

NOT gates

NAND gates

AND gates

60. Symbol represents

NOR gate

XNOR gate

NOT gate

NAND gate

61. Photovoltaic cell produces electrical energy from

Light energy

Chemical energy

None of these

Heat energy

62. 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

Diode is forward based

Diode is reverse biased

Potential barrier in depletion layer remains unchanged

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

Or gates and NOT gates

AND gates and NOT gates

OR gates only

AND gates, OR gates, and NOT gates

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

Antimony

Phosphorus

Aluminum

Arsenic

65. 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

None of these

Reversed biased

Zero biased

Forward biased

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

p-type

Intrinsic

Extrinsic

n-type

67. In Germanium crystal, impurity donor elements have valiancy

68. A transistor consists of

One PN-junction

Two PN-junctions

Three PN-junctions

Four PN-junctions

69. In Germanium crystal, impurity donor elements have valiancy

70. 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

71. In half wave rectification

Current flows in pulses

Current flows in one directions

None of these

Only half cycle is used

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

NAND gate

NOT gate

OR gate

AND gate

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

9.8

4.9

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

Decreases and then increases

Increases

Decreases

Remains unchanged

75. 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

76. Which one is forward bias?

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

Almost negligible

Zero

Very low

Very high

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

Filter

Oscillator

Amplifier

Logic gates

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

any of above

mix

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

Neutrons

Electrons

Holes

Protons

81. n-type semiconductor if formed

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

From pure Ge crystal

From pure Si crystal

82. To use a transistor as an amplifier

Both junctions are forward biased

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

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

Increases

First A and B

Decreases

Remains constant

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

Doping density

Forward bias

Diode design

Temperature

85. NAND gate is

A universal gate

A basic universal gate

Not a universal gate

A basic gate

86. In semiconductors at a room temperature

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

The valence band is completely filled

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

Holes move from emitter be base

Electrons move from base to collector

Holes move from base to emitter

Holes move from emitter to base

88. The least doped region in a transistor is

Base

Emitter

Collector

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

Diffusion of charges

Drift of charges

Depends upon the nature of material

Both drift and diffusion of charges

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

Potential is zero

Potential is maximum

Electric field is zero

Electric field is maximum

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

Non-inverting voltage at output

Reference voltage on the other

Output

Virtual input

92. The forward resistance of the diode is

Few ohms

Many ohms

None of these

Ohms

93. 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

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

Slightly less than emitter current

Greater than emitter current

Equal to emitter current

Any of above

95. Depletion region of a junction is formed

During the manufacturing process

Under reverse bias

Under forward bias

When temperature varies

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

None of these

Millisecond

Microsecond

Nanosecond

97. Young’s modulus for copper is

None of these

70 x 10 Nm¯²

91 x 10 Nm¯²

110 Nm¯²

98. A diode as a rectifier converts:

D.C. into A.C.

Low voltage to high voltage

High voltage to low voltage

A.C. into D.C.

99. In a n-p-n transistor:

Holes move from base to collector

Negative charge moves from collector to base

Negative charge moves from emitter to base

Holes move from emitter to base

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

Emitter

Base

Collector

None of these

101. An OP-AMPs can amplify

Both A.C. & D.C.

D.C.

A.C.

None of these

102. Photodiode is used for

None of these

Emission of light

Light display

Detection of light

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

Boron

Gallium

All of above

Aluminum

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

Force

None of these

Stress

Strain

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

Intrinsic

n-type

Extrinsic

p-type

106. Which logic gate is represented by following diagram?

EOR

AND

NOR

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

Increases its electrical conductivity

Increase its electrical resistivity

Enable it to Telerate higher voltage

Increase its life

108. LDR means:

None of these

Low degree radiations

Light dependent resistance

Low degree resistor

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

Oscillator

Amplifier

Filter

Logic gates

110. Radio waves of constant amplitude can be generated with

Oscillator

FET

Rectifier

Filter

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

Each of them increases

Copper decreases and germanium increases

Copper increases and germanium decreases

Each of them decreases

112. Light emitting diode work when it is

Forward biases

Reverse biased

None of these

Both

113. Identify the correct statement about minority carriers

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

Free electrons in n-type and p-type

Holes in n-type and p-type

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

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

N-type conductor

N-type semiconductor

P-type semiconductor

None of these

115. The thickness of the base is equal to

Mean of thickness of emitter and collector

Thickness of emitter

Thickness of collector

Very small as compared to the thickness of emitter and collector

116. 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

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

Conductor

Alloy

Semiconductor

Insulator

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

Missing electrons

Extra electrons

Neutrons

Protons

119. A n-p-n transistor conducts when

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

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

Both collector and emitter are positive with respect to the base

Both collector and emitter are negative with respect to the base

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

Ohms

Several mega ohms

Mega ohms

Kilo ohms

121. 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

122. The operation of a transistor requires

That the base be heated

That the emitter be heated

That the collector be heated

None of these

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

Can be any of the above three

Base

Emitter

Collector

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

Computers

Electric generations

Transformers

Electric motors

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

Extra electrons

Protons

Missing of electrons

Neutrons

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

n-type conductor

p-type semiconductor

n-type semiconductor

p-type conductor

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

Infinity

Zero

Almost zero

None of these

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

Remains unchanged

Increases

Decreases and then increases

Decreases

129. Semi-conductor germanium and silicon are

Pentavalent

Trivalent

Divalent

Tetravalent

130. Depletion layer consists of

Electrons

Protons

Mobile ions

Immobile ions

131. Arsenic, antimony or phosphorus are impurities of

p-type

may be p-type or n-type

n-type

None of these

132. In a P-type semiconductor

Major current carriers are mobile holes

Major current carriers are electrons

Major current carriers are mobile negative ions

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

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

Unit cell

Ore

All of these

Crystal lattice

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

None of these

Low

High

Zero

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

Base

Collector

Emitter

Any of above

136. 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

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

Compress ional stress

Shear stress

None of these

Tensile stress

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

Require more current

Damaged

Works efficiently

None of these

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

Collector

Emitter

Base

Any of the above depending on nature of transistor

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

Of zero

Less than one

Greater than one

Equal to one

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

Increased by reverse biasing

Is independent of voltage

Increased by forward biasing

Decreased by reverse biasing

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

Charged region

Diffusion region

Depletion region

None of these

143. 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

Its conductivity increases with rise of temperature

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

144. N-type crystal is

Negative charged

Neutral

None of these

Positively charged

145. The positive sign of gain indicates that

May be in phase or not

None of these

Input and out signals are not in phase

Input and out signals are in phase

146. Diode can work as

Multivibrator

Rectifier

Modulator

Oscillator

147. Application of photodiode is/are

Logic gates

Automatic switching

None of these

Detection of visible and invisible radiations

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

Blockers

Majority carriers

Dual carriers

Minority carriers

149. In forward bias the width of potential barrier

No effect

Decreases

Increases

Remains same

150. 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

Each of them decreases

Copper increases and germanium decreases

151. 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

152. 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

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

AND gate

XOR gate

OR gate

NOT gate

154. 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

155. A NAND gate has:

LOW inputs and a HIGH output

LOW inputs and a LOW output

HIGH inputs and a HIGH output

None of these

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

Semiconductor

Insulator

None of these

Superconductor

157. Which one is reverse-biased?

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

Strain

Force

None of these

Stress

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

P-type material

Oscillator

Amplifier

Rectifier

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

Increase the majority carrier current

Lowers the potential barrier

Raises the potential barrier

Increase the minority carrier current

161. In a P-type semiconductor

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

Major current carriers are mobile negative ions

Major current carriers are electrons

Major current carriers are mobile holes

162. 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

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

Detector

None of these

Oscillator

Rectifier

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

Transverse Waves

x-rays

Electromagnetic Waves

Gamma Rays

165. The ratio β represents

166. Transistor can be used as

Amplifier

Filter

Half wave rectifier

Full wave rectifier

167. With negative feedback, the returning signal:

Opposes the input signal

Is proportional to differential voltage gain

Is proportional to output current

Aids the input signal

168. In insulators

Conduction band is empty and valence band is filled with electrons

Conduction band is partially filled with electrons

Valence band is partially filled with electrons

Conduction band is filled with electrons and valence bad is empty

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

Gallium

Boron

Aluminum

All of these

170. The number of junctions in the PNP transistor are

171. The energy band gap is maximum in

Superconductors

Insulators

Metals

Semiconductors

172. 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.

173. Polythene, potystrene and nylon are examples of

Crystalline solids

Glassy solids

Amorphous solids

Polymeric solids

174. When the output of OR gate is 1

Only if both inputs are 1

If either or both inputs are 1

If either input is zero

If both inputs are zero

175. The working of transistor as amplifier is similar to

Step down transformer

Step up transformer

Three diodes in common

Triode vacuum tube

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

p-type

Superconductor

n-type

Insulator

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

In forward bias

To A.C.

In reverse bias

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

ECAT Physics Electronics MCQS Online Test

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