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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

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

Diode design

Forward bias

Doping density

Temperature

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

OR gates only

Or gates and NOT gates

AND gates and NOT gates

AND gates, OR gates, and NOT gates

3. Reverse bias applied on a junction diode

Increase the minority carrier current

Increases the majority carrier current

Lowers the potential barrier

Raises the potential barrier

4. In p-type semiconductor

Major carrier is mobile negative ions

The number of mobile holes exceeds the number of acceptors

Major current carrier is electrons

Major carrier is mobile holes

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

Decreases

First A and B

Remains constant

Increases

6. 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

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

Protons and electrons

Holes and electrons

Electrons and holes

Electrons and protons

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

Almost zero

Infinity

None of these

Zero

9. In half wave rectification

None of these

Current flows in pulses

Only half cycle is used

Current flows in one directions

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

Works efficiently

Damaged

Require more current

None of these

11. Symbol represents

NAND gate

NOT gate

XNOR gate

NOR gate

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

Unit cell

All of these

Crystal lattice

Ore

13. The positive sign of gain indicates that

Input and out signals are in phase

May be in phase or not

Input and out signals are not in phase

None of these

14. Radio waves of constant amplitude can be generated with

Oscillator

Rectifier

Filter

FET

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

Depletion region

None of these

Diffusion region

Charged region

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

In reverse bias

In forward bias

None of these

To A.C.

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

Equal number of free electrons and holes

Large number of holes and few electrons

Large number of free electrons and few holes

Large number of holes and electrons

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

Aluminum

Boron

All of these

Gallium

19. Identify the correct statement about minority carriers

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

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

Holes in n-type and p-type

Free electrons in n-type and p-type

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

Neutrons

Holes

Protons

Electrons

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

None of these

Strain

Force

Stress

22. At absolute zero, Si acts as

Non-metal

Insulator

None of these

Metal

23. Which one is reverse-biased?

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

Conductors

Insulators

Semiconductors

Superconductors

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

Boron

Aluminum

Phosphorus

Gold

26. 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

27. Light emitting diode work when it is

Both

None of these

Reverse biased

Forward biases

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

n-type semiconductor

p-type conductor

n-type conductor

p-type semiconductor

29. 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

Diode is neutralized

None of these

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

Nanosecond

None of these

Microsecond

Millisecond

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

Electrons move from base to collector

Holes move from emitter be base

Holes move from emitter to base

Holes move from base to emitter

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

Super conductor

N-type material

Semiconductor

P-type material

33. In Germanium crystal, impurity donor elements have valiancy

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

Diffusion of charges

Depends upon the nature of material

Drift of charges

Both drift and diffusion of charges

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

Collector

Emitter

Base

Any of above

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

Arsenic

Aluminum

Phosphorus

Antimony

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

Resistor is used

Capacitor is used

Solvent is used

None of these

38. 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

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

Stress

Force

None of these

Strain

40. 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

Reversed biased

Forward biased

Zero biased

None of these

41. Acceptor and donor impurities donate

p-carriers only

p-carriers and n-carriers respectively

n-carriers only

n-carriers and p-carriers respectively

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

Aluminum

Arsenic

Antimony

Phosphorus

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

Collector

Any of the above depending on nature of transistor

Emitter

Base

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

Variable amplitude

Zero amplitude

Constant amplitude

Unit amplitude

45. 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 & high resistance when reverse biased

It has low resistance to the current flow when forward biased

46. In Germanium crystal, impurity donor elements have valiancy

47. In semiconductors at a room temperature

The valence band is completely filled

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

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

The conduction band is completely empty

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

Comparator

OR gate

AND gate

INVERTER gate

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

Inverting terminal is at high potential

Both are at the high potential

Both are at the same potential

Non-inverting terminal is at high potential

50. Polythene, potystrene and nylon are examples of

Crystalline solids

Glassy solids

Amorphous solids

Polymeric solids

51. The least doped region in a transistor is

Emitter

Base

Collector

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

Off switch

Capacitor

Inductor

On switch

53. Which logic gate is represented by following diagram?

AND

EOR

NOR

54. Transistor can be used as

Half wave rectifier

Amplifier

Full wave rectifier

Filter

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

Extrinsic

p-type

Intrinsic

n-type

56. N-type crystal is

Neutral

None of these

Positively charged

Negative charged

57. In forward bias the width of potential barrier

No effect

Remains same

Decreases

Increases

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

Diode

Amplifier

Rectifier

Transistor

59. LDR means:

Low degree resistor

Light dependent resistance

None of these

Low degree radiations

60. Which one is forward bias?

61. Which is normal used of transistor?

Rectifier

Switching device

P-type material

Diode

62. The forward resistance of the diode is

Few ohms

Ohms

Many ohms

None of these

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

9.8

4.9

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

Common base configuration

None of these

Common collector configuration

Common emitter configuration

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

The switch

The light emitting diode

The photo diodes

Solar cells

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

It offers a very low open loop gain all of above

It offers a very high inputs resistance to the input current

None of these

It offers a very low output resistance

67. Photovoltaic cell produces electrical energy from

Heat energy

Light energy

Chemical energy

None of these

68. Application of photodiode is/are

None of these

Automatic switching

Logic gates

Detection of visible and invisible radiations

69. 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

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

Valence electrons

None of these

Free electrons

Tightly bound electrons

71. Young’s modulus for copper is

91 x 10 Nm¯²

None of these

70 x 10 Nm¯²

110 Nm¯²

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

120° Phase shift

90° Phase shift

No Phase shift

180° Phase shift

73. The least doped region in a transistor is

Either emitter or collector

Base

Collector

Emitter

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

Logic gates

Amplifier

Oscillator

Filter

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

P-type semiconductor

N-type semiconductor

None of these

N-type conductor

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

Bulk modulus

None of these

Shear modulus

Young’s modulus

77. Arsenic, antimony or phosphorus are impurities of

may be p-type or n-type

n-type

None of these

p-type

78. At absolute zero, Si acts as

Non-metal

Metal

None of these

Insulator

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

n-type conductor

n-type semiconductor

p-type conductor

p-type semiconductor

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

Neutrons

Extra electrons

Missing of electrons

Protons

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

Emitter

None of these

Collector

Base

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

Blockers

Majority carriers

Minority carriers

Dual carriers

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

Equal to one

Greater than one

Less than one

Of zero

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

0.67 V

0.9 V

0.5 V

0.7 V

85. Depletion layer consists of

Mobile ions

Protons

Immobile ions

Electrons

86. 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 HIGH

All inputs are LOW

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

10¯⁶ cm

1 mm

1 cm

10¯¹² cm

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

9.8

4.9

89. 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 bad is empty

Conduction band is partially filled with electrons

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

Suppressing the harmonics in A.C voltage

Using a Coolidge tube

Suppressing half wave of A.C supply by using diode

Using a transistor

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

Amplifier

Rectifier

P-type material

Oscillator

92. 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

93. Reverse bias applied on a junction diode

Increase the minority carrier current

Raises the potential barrier

Increases the majority carrier current

Lowers the potential barrier

94. An OP-AMPs can amplify

D.C.

Both A.C. & D.C.

A.C.

None of these

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

Neutrons

Protons

Extra electrons

Missing electrons

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

Enable it to Telerate higher voltage

Increases its electrical conductivity

Increase its electrical resistivity

Increase its life

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

Compress ional stress

Tensile stress

Shear stress

None of these

98. A transistor consists of

One PN-junction

Three PN-junctions

Two PN-junctions

Four PN-junctions

99. In a n-p-n transistor:

Holes move from base to collector

Holes move from emitter to base

Negative charge moves from collector to base

Negative charge moves from emitter to base

100. 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

101. A substance which have empty conduction band is called

Semiconductor

Conductor

Insulator

None of these

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

Magnification

Amplification

Rectification

All of these

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

Man hundred

Hundreds

None of these

Thousands

104. n-type semiconductor if formed

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

From pure Ge crystal

From pure Si crystal

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

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

OR gate

NOT gate

AND gate

XOR gate

106. The operation of a transistor requires

That the base be heated

None of these

That the emitter be heated

That the collector be heated

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

Converter

Filtering circuit

A rectifier

An amplifier

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

Aluminum

All of above

Gallium

Boron

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

Remains unchanged

Increases

Decreases and then increases

Decreases

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

Conductor

Semiconductor

Alloy

Insulator

111. A NAND gate has:

LOW inputs and a HIGH output

LOW inputs and a LOW output

None of these

HIGH inputs and a HIGH output

112. 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

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

Very high

Zero

Almost negligible

Very low

114. NAND gate is

A basic gate

A basic universal gate

A universal gate

Not a universal gate

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

Potential is zero

Electric field is maximum

Potential is maximum

Electric field is zero

116. Diode can work as

Rectifier

Multivibrator

Modulator

Oscillator

117. To use a transistor as an amplifier

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

No bias voltages are required

Both junctions are reverse biased

Both junctions are forward biased

118. 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

119. In a semiconductor, the mobility of holes is

Less than electrons

None

Greater than electrons

Equal to electrons

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

n-type

p-type

Intrinsic

Extrinsic

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

Large number of holes and electrons

Large number of free electrons and few holes

Equal number of free electrons and holes

Large number of holes and few electrons

122. The thickness of the base is equal to

Thickness of emitter

Very small as compared to the thickness of emitter and collector

Mean of thickness of emitter and collector

Thickness of collector

123. In a PN junction

Undetermined

High potential at N side and low potential at P side

P and N both are at same potential

High potential at P side and low potential at N side

124. When n-type of semiconductor is heated,

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

Number of electrons and holes remains same

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

Transverse Waves

Electromagnetic Waves

x-rays

Gamma Rays

126. Photodiode is used for

None of these

Light display

Emission of light

Detection of light

127. 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 decreases

Each of them increases

Copper increases and germanium decreases

128. When the output of OR gate is 1

If either or both inputs are 1

Only if both inputs are 1

If either input is zero

If both inputs are zero

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

Superconductor

Insulator

Semiconductor

None of these

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

Decreases

Remains unchanged

Decreases and then increases

Increases

131. The ratio β shows the

Voltage gain

None of these

Current gain

Input resistance

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

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

Wide

Zero

Narrow

Infinity

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

Increase its electrical resistivity

Increase its life

Enable it to Telerate higher voltage

Increase its electrical conductivity

135. 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

AND gate

NOR gate

136. Zener breakdown in a semiconductor diode occurs when

Reverse bias exceeds certain value

Forward current exceeds certain value

Forward bias exceeds certain value

Potential barrier is reduced to zero

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

Electric generations

Electric motors

Computers

Transformers

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

Amplifier

Oscillator

Filter

Logic gates

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

Bulk’s modulus

Young’s modulus

Modulus of electricity

None of these

140. The working of transistor as amplifier is similar to

Triode vacuum tube

Step down transformer

Three diodes in common

Step up transformer

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

Phosphorus

Arsenic

Antimony

Indium

142. 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

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

Decreased by reverse biasing

Increased by reverse biasing

Is independent of voltage

Increased by forward biasing

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

n-type

p-type

Superconductor

Insulator

145. 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

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

Greater than emitter current

Equal to emitter current

Slightly less than emitter current

Any of above

147. 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

148. The energy band gap is maximum in

Semiconductors

Metals

Insulators

Superconductors

149. 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 mobile holes

Major current carriers are electrons

150. The number of junctions in the PNP transistor are

151. Non-inverting amplifier circuits have

A very low input impedance

None of these

A low output impedance

A very high input impedance

152. 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

153. The ratio β represents

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

Resistance of both increases

Resistance of copper decreases while that of germanium increases

Resistance of both decreases

Resistance of copper increases while that of germanium decreases

155. 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

156. When NPN transistor is used as an amplifier

Electrons move from emitter to base

Electrons move from base to emitter

Electrons move from collector to base

Holes move from base to emitter

157. In a n-p-n transistor:

Negative charge moves from collector to base

Holes move from base to collector

Holes move from emitter to base

Negative charge moves from emitter to base

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

Suddenly increases

Remain fixed

Increases slowly

Decreases slowly

159. 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

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

any of above

mix

161. The critical temperature for mercury is

7.2 K

3.72 K

1.18 K

4.2 K

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

None of these

Detector

Oscillator

Rectifier

163. 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

Forbidden energy states

None of these

Hidden energy states

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

Low

None of these

Zero

High

165. A diode as a rectifier converts:

Low voltage to high voltage

A.C. into D.C.

High voltage to low voltage

D.C. into A.C.

166. A diode as a rectifier converts:

Low voltage to high voltage

A.C. into D.C.

High voltage to low voltage

D.C. into A.C.

167. Depletion region of a junction is formed

During the manufacturing process

Under forward bias

Under reverse bias

When temperature varies

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

Increase the majority carrier current

Increase the minority carrier current

Raises the potential barrier

Lowers the potential barrier

169. The energy band gap is maximum in

Metals

Insulators

Superconductors

Semiconductors

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

Extra electrons

Neutrons

Missing electrons

Protons

171. In the transistor schematic symbol, the arrow

Point from north to south

Is located on the base

Is located on the emitter

Is locate on the collector

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

None of these

Holes

Neutrons

Electrons

173. 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

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

NOT gates

OR gates

NAND gates

AND gates

175. With negative feedback, the returning signal:

Opposes the input signal

Is proportional to differential voltage gain

Aids the input signal

Is proportional to output current

176. Semi-conductor germanium and silicon are

Pentavalent

Divalent

Trivalent

Tetravalent

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

Reference voltage on the other

Non-inverting voltage at output

Output

Virtual input

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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

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