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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 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

2. Zener breakdown in a semiconductor diode occurs when

Forward bias exceeds certain value

Forward current exceeds certain value

Potential barrier is reduced to zero

Reverse bias exceeds certain value

3. A n-p-n transistor conducts when

Both collector and emitter are 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

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

4. 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

5. In half wave rectification

Only half cycle is used

Current flows in one directions

Current flows in pulses

None of these

6. The critical temperature for mercury is

1.18 K

3.72 K

7.2 K

4.2 K

7. The ratio β represents

8. Which logic gate is represented by following diagram?

AND

EOR

NOR

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

Both are at the high potential

Inverting terminal is at high potential

Both are at the same potential

Non-inverting terminal is at high potential

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

Antimony

Aluminum

Arsenic

Phosphorus

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

Unit amplitude

Constant amplitude

Variable amplitude

Zero amplitude

12. Light emitting diode work when it is

Both

Reverse biased

Forward biases

None of these

13. 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

14. The energy band gap is maximum in

Semiconductors

Insulators

Superconductors

Metals

15. Arsenic, antimony or phosphorus are impurities of

n-type

p-type

None of these

may be p-type or n-type

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

Extra electrons

Neutrons

Missing electrons

Protons

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

Hundreds

Thousands

None of these

Man hundred

18. Reverse bias applied on a junction diode

Raises the potential barrier

Increase the minority carrier current

Increases the majority carrier current

Lowers the potential barrier

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

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

Reference voltage on the other

Virtual input

Non-inverting voltage at output

Output

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

Drift of charges

Depends upon the nature of material

Diffusion of charges

Both drift and diffusion of charges

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

Semiconductor

Super conductor

P-type material

N-type material

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

Suppressing half wave of A.C supply by using diode

Using a transistor

Suppressing the harmonics in A.C voltage

Using a Coolidge tube

24. The least doped region in a transistor is

Emitter

Base

Collector

25. The energy band gap is maximum in

Semiconductors

Insulators

Metals

Superconductors

26. 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

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

Young’s modulus

None of these

Modulus of electricity

Bulk’s modulus

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

The photo diodes

The light emitting diode

The switch

Solar cells

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

None of these

Valence electrons

Tightly bound electrons

Free electrons

30. A transistor consists of

One PN-junction

Three PN-junctions

Four PN-junctions

Two PN-junctions

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

10¯⁶ cm

1 mm

10¯¹² cm

1 cm

32. 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

33. 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

34. The operation of a transistor requires

That the base be heated

That the collector be heated

None of these

That the emitter be heated

35. Symbol represents

NAND gate

NOT gate

XNOR gate

NOR gate

36. Which one is reverse-biased?

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

Aluminum

All of these

Gallium

Boron

38. Transistor can be used as

Full wave rectifier

Amplifier

Half wave rectifier

Filter

39. Photodiode is used for

Light display

Emission of light

None of these

Detection of light

40. Depletion layer consists of

Immobile ions

Protons

Mobile ions

Electrons

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

Transverse Waves

Electromagnetic Waves

Gamma Rays

x-rays

42. 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

NOR

AND

43. In forward bias the width of potential barrier

Remains same

No effect

Decreases

Increases

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

AND gates

NAND gates

NOT gates

OR gates

45. 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 open loop gain all of above

It offers a very low output resistance

None of these

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

Base

Collector

Any of the above depending on nature of transistor

Emitter

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

p-type semiconductor

p-type conductor

n-type semiconductor

n-type conductor

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

Doping density

Forward bias

Temperature

Diode design

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

Rectifier

P-type material

Amplifier

Oscillator

50. N-type crystal is

None of these

Positively charged

Neutral

Negative charged

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

p-type

Insulator

Superconductor

n-type

52. Non-inverting amplifier circuits have

None of these

A very low input impedance

A very high input impedance

A low output impedance

53. Semi-conductor germanium and silicon are

Tetravalent

Divalent

Trivalent

Pentavalent

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

Rectifier

Amplifier

Diode

Transistor

55. 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 negative ions

Major current carriers are mobile holes

56. In insulators

Conduction band is filled with electrons and valence bad is empty

Conduction band is partially filled with electrons

Valence band is partially filled with electrons

Conduction band is empty and valence band is filled with electrons

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

All inputs are LOW

All inputs are HIGH

At least one input is HIGH

At least one input is LOW

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

Boron

Gold

Phosphorus

Aluminum

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

any of above

mix

60. 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

Diode is forward based

Potential barrier in depletion layer increases

Potential barrier in depletion layer remains unchanged

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

In reverse bias

To A.C.

None of these

In forward bias

62. 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

63. 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

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

Filter

Oscillator

Logic gates

Amplifier

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

Remains unchanged

Decreases and then increases

Decreases

Increases

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

Oscillator

None of these

Detector

Rectifier

67. Which is normal used of transistor?

P-type material

Diode

Switching device

Rectifier

68. n-type semiconductor if formed

From pure Si 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

From pure Ge crystal

69. 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

OR gate

NOR gate

AND gate

70. A diode as a rectifier converts:

High voltage to low voltage

D.C. into A.C.

A.C. into D.C.

Low voltage to high voltage

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

Infinity

Zero

Wide

Narrow

72. A substance which have empty conduction band is called

Conductor

Insulator

None of these

Semiconductor

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

Holes

Electrons

Neutrons

None of these

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

INVERTER gate

Comparator

OR gate

AND gate

75. At absolute zero, Si acts as

Metal

Insulator

Non-metal

None of these

76. The number of junctions in the PNP transistor are

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

Or gates and NOT gates

AND gates, OR gates, and NOT gates

OR gates only

AND gates and NOT gates

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

Inductor

On switch

Capacitor

Off switch

79. Acceptor and donor impurities donate

n-carriers only

p-carriers only

n-carriers and p-carriers respectively

p-carriers and n-carriers respectively

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

Millisecond

None of these

Microsecond

Nanosecond

81. The forward resistance of the diode is

Many ohms

None of these

Ohms

Few ohms

82. In a n-p-n transistor:

Holes move from emitter to base

Negative charge moves from collector to base

Holes move from base to collector

Negative charge moves from emitter to base

83. 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

84. The positive sign of gain indicates that

May be in phase or not

Input and out signals are not in phase

Input and out signals are in phase

None of these

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

Increase its electrical resistivity

Enable it to Telerate higher voltage

Increases its electrical conductivity

Increase its life

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

Insulator

None of these

Semiconductor

Superconductor

87. In the transistor schematic symbol, the arrow

Point from north to south

Is located on the base

Is locate on the collector

Is located on the emitter

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

Strain

None of these

Stress

Force

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

Suddenly increases

Decreases slowly

Increases slowly

Remain fixed

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

None of these

Shear stress

Compress ional stress

Tensile stress

91. The working of transistor as amplifier is similar to

Step up transformer

Step down transformer

Three diodes in common

Triode vacuum tube

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

Resistance of both decreases

Resistance of both increases

Resistance of copper decreases while that of germanium increases

Resistance of copper increases while that of germanium decreases

93. 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

94. Diode can work as

Modulator

Multivibrator

Oscillator

Rectifier

95. 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 band is empty

96. Depletion region of a junction is formed

Under reverse bias

Under forward bias

When temperature varies

During the manufacturing process

97. Young’s modulus for copper is

110 Nm¯²

None of these

70 x 10 Nm¯²

91 x 10 Nm¯²

98. Photovoltaic cell produces electrical energy from

Light energy

None of these

Heat energy

Chemical energy

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

Less than one

Equal to one

Greater than one

Of zero

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

Increases

Remains constant

Decreases

First A and B

101. In p-type semiconductor

The number of mobile holes exceeds the number of acceptors

Major carrier is mobile negative ions

Major carrier is mobile holes

Major current carrier is electrons

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

Increase its electrical resistivity

Increase its life

Increase its electrical conductivity

Enable it to Telerate higher voltage

103. In a P-type semiconductor

Major current carriers are mobile negative ions

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

Major current carriers are electrons

Major current carriers are mobile holes

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

Intrinsic

p-type

n-type

Extrinsic

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

Electric field is zero

Electric field is maximum

Potential is maximum

Potential is zero

106. 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

None of these

Zero biased

Reversed biased

107. 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 maximum

Potential is zero

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

4.9

9.8

109. When n-type of semiconductor is heated,

Number of holes increases while that of holes decreases

Number of electrons and holes increases equally

Number of electrons increases while that of holes decreases

Number of electrons and holes remains same

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

p-type semiconductor

p-type conductor

n-type conductor

n-type semiconductor

111. Reverse bias applied on a junction diode

Raises the potential barrier

Increases the majority carrier current

Lowers the potential barrier

Increase the minority carrier current

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

None of these

Almost zero

Infinity

Zero

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

Lowers the potential barrier

Increase the majority carrier current

Increase the minority carrier current

Raises the potential barrier

114. Polythene, potystrene and nylon are examples of

Crystalline solids

Polymeric solids

Amorphous solids

Glassy solids

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

Base

Emitter

Can be any of the above three

Collector

116. To use a transistor as an amplifier

Both junctions are reverse biased

No bias voltages are required

Both junctions are forward biased

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

117. 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

None of these

Diode is reverse biased

Diode is forward biased

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

None of these

Damaged

Require more current

Works efficiently

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

0.5 V

0.7 V

0.9 V

0.67 V

120. 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

121. 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

122. When NPN transistor is used as an amplifier

Electrons move from emitter to base

Electrons move from collector to base

Electrons move from base to emitter

Holes move from base to emitter

123. In Germanium crystal, impurity donor elements have valiancy

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

An amplifier

A rectifier

Converter

Filtering circuit

125. 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

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

None of these

Common emitter configuration

Common collector configuration

Common base configuration

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

Antimony

Indium

Phosphorus

Arsenic

128. 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

None of these

Band levels

Forbidden energy states

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

Blockers

Minority carriers

Dual carriers

Majority carriers

130. 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

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

Zero

Low

None of these

High

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

AND gate

NOT gate

OR gate

XOR gate

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

Semiconductors

Superconductors

Conductors

Insulators

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

Holes move from emitter to base

Holes move from base to emitter

Holes move from emitter be base

Electrons move from base to collector

135. Identify the correct statement about minority carriers

Free electrons in n-type and p-type

Holes 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

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

Protons

Electrons

Holes

Neutrons

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

Amplifier

Logic gates

Filter

Oscillator

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

Stress

Force

None of these

Strain

139. Radio waves of constant amplitude can be generated with

FET

Oscillator

Filter

Rectifier

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

Gallium

All of above

Aluminum

Boron

141. At absolute zero, Si acts as

Non-metal

Insulator

Metal

None of these

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

p-type conductor

n-type conductor

p-type semiconductor

n-type semiconductor

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

Antimony

Aluminum

Phosphorus

Arsenic

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

Young’s modulus

Bulk modulus

None of these

Shear modulus

145. In semiconductors at a room temperature

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

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

The conduction band is completely empty

The valence band is completely filled

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

Equal to emitter current

Any of above

Greater than emitter current

Slightly less than emitter current

147. NAND gate is

A basic universal gate

Not a universal gate

A universal gate

A basic gate

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

Decreases and then increases

Decreases

Remains unchanged

Increases

149. When the output of OR gate is 1

If either input is zero

If both inputs are zero

Only if both inputs are 1

If either or both inputs are 1

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

Extrinsic

Intrinsic

p-type

n-type

151. 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

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

9.8

4.9

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

Insulator

Conductor

Alloy

Semiconductor

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

Protons

Neutrons

Missing electrons

Extra electrons

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

Very high

Very low

Almost negligible

Zero

156. Which one is forward bias?

157. In a semiconductor, the mobility of holes is

Less than electrons

Equal to electrons

Greater than electrons

None

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

Collector

Emitter

Base

Can be any of the above three

159. An OP-AMPs can amplify

Both A.C. & D.C.

None of these

A.C.

D.C.

160. The least doped region in a transistor is

Collector

Either emitter or collector

Base

Emitter

161. 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

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

Electric motors

Computers

Transformers

Electric generations

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

Extra electrons

Neutrons

Protons

Missing of electrons

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

Any of above

Base

Collector

Emitter

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

All of these

Unit cell

Crystal lattice

Ore

166. LDR means:

Low degree resistor

Low degree radiations

Light dependent resistance

None of these

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

180° Phase shift

No Phase shift

90° Phase shift

120° Phase shift

168. A NAND gate has:

HIGH inputs and a HIGH output

LOW inputs and a LOW output

None of these

LOW inputs and a HIGH output

169. The ratio β shows the

Current gain

Input resistance

Voltage gain

None of these

170. 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

Copper decreases and germanium increases

Each of them decreases

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

Resistor is used

Capacitor is used

None of these

Solvent is used

172. In Germanium crystal, impurity donor elements have valiancy

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

Amplification

Rectification

Magnification

All of these

174. Application of photodiode is/are

Detection of visible and invisible radiations

Logic gates

None of these

Automatic switching

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

Collector

None of these

Emitter

Base

176. The thickness of the base is equal to

Very small as compared to the thickness of emitter and collector

Thickness of emitter

Thickness of collector

Mean of thickness of emitter and collector

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

Is independent of voltage

Increased by reverse biasing

Decreased by reverse biasing

Increased by forward biasing

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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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