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MDCAT Physics Electronics Test Online

Malik TahirLast Updated: May 26, 2025

Physics Electronics MCQS Online Test

MDCAT 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:	MDCAT Entry Test Physics Online Test Interview Questions about Physics All Universities Entrance Test Recruitments Tests

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

NAND gates

OR gates

AND gates

NOT gates

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

Stress

Strain

Force

None of these

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

High

None of these

Low

Zero

4. 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

5. A piece 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

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

NOT gate

AND gate

NAND gate

OR gate

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

Holes move from emitter be base

Holes move from base to emitter

Holes move from emitter to base

Electrons move from base to collector

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

Increases

Remains constant

Decreases

First A and B

9. 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

10. At absolute zero, Si acts as

Metal

None of these

Insulator

Non-metal

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

Potential is zero

Potential is maximum

Electric field is maximum

Electric field is zero

12. In a semiconductor, the mobility of holes is

Equal to electrons

None

Greater than electrons

Less than electrons

13. An OP-AMPs can amplify

A.C.

Both A.C. & D.C.

D.C.

None of these

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

The light emitting diode

The switch

The photo diodes

Solar cells

15. 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

Diode is neutralized

Diode is forward biased

None of these

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

Phosphorus

Aluminum

Arsenic

Antimony

17. Which logic gate is represented by following diagram?

NOR

AND

EOR

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

Phosphorus

Antimony

Arsenic

Indium

19. The positive sign of gain indicates that

Input and out signals are in phase

None of these

Input and out signals are not in phase

May be in phase or not

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

Increase its electrical conductivity

Enable it to Telerate higher voltage

Increase its life

Increase its electrical resistivity

21. 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 and the conduction band is partially filled

The valence band is completely filled

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

Increased by reverse biasing

Decreased by reverse biasing

Increased by forward biasing

Is independent of voltage

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

Magnification

Amplification

Rectification

All of these

24. A diode as a rectifier converts:

High voltage to low voltage

A.C. into D.C.

Low voltage to high voltage

D.C. into A.C.

25. Which is normal used of transistor?

Rectifier

Diode

Switching device

P-type material

26. Reverse bias applied on a junction diode

Raises the potential barrier

Increases the majority carrier current

Increase the minority carrier current

Lowers the potential barrier

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

Extra electrons

Missing of electrons

Protons

Neutrons

28. Which one is forward bias?

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

120° Phase shift

180° Phase shift

90° Phase shift

No Phase shift

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

Majority carriers

Dual carriers

Minority carriers

Blockers

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

Common emitter configuration

Common collector configuration

Common base configuration

None of these

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

mix

any of above

33. 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

Copper increases and germanium decreases

Each of them increases

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

Stress

None of these

Force

Strain

35. In a P-type semiconductor

Major current carriers are mobile holes

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

Major current carriers are mobile negative ions

Major current carriers are electrons

36. 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.

37. Acceptor and donor impurities donate

n-carriers only

p-carriers and n-carriers respectively

n-carriers and p-carriers respectively

p-carriers only

38. Which one is reverse-biased?

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

Damaged

Works efficiently

None of these

Require more current

40. Polythene, potystrene and nylon are examples of

Polymeric solids

Crystalline solids

Glassy solids

Amorphous solids

41. In Germanium crystal, impurity donor elements have valiancy

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

Transformers

Electric motors

Electric generations

Computers

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

Zero amplitude

Unit amplitude

Variable amplitude

Constant amplitude

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

Holes and electrons

Protons and electrons

Electrons and holes

Electrons and protons

45. 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

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

Filter

Logic gates

Amplifier

Oscillator

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

Very low

Almost negligible

Very high

Zero

48. Photovoltaic cell produces electrical energy from

Heat energy

Chemical energy

Light energy

None of these

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

Protons

Neutrons

Holes

Electrons

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

Zero

Infinity

Wide

Narrow

51. The ratio β represents

52. 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

53. n-type semiconductor if formed

From pure Ge crystal

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

From pure Si crystal

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

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

Capacitor is used

None of these

Solvent is used

Resistor is used

55. The energy band gap is maximum in

Superconductors

Metals

Semiconductors

Insulators

56. 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

Emitter

Collector

Base

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

Gallium

All of these

Aluminum

Boron

58. With negative feedback, the returning signal:

Aids the input signal

Is proportional to differential voltage gain

Is proportional to output current

Opposes the input signal

59. The energy band gap is maximum in

Semiconductors

Insulators

Metals

Superconductors

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

Aluminum

Boron

All of above

Gallium

61. In semiconductors at a room temperature

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

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

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

Electric field is zero

Potential is maximum

Electric field is maximum

Potential is zero

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

Remain fixed

Suddenly increases

Increases slowly

Decreases slowly

64. Depletion layer consists of

Immobile ions

Protons

Mobile ions

Electrons

65. A NAND gate has:

LOW inputs and a LOW output

LOW inputs and a HIGH output

HIGH inputs and a HIGH output

None of these

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

Amplifier

Filter

Oscillator

Logic gates

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

None of these

Superconductor

Semiconductor

Insulator

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

Any of the above depending on nature of transistor

Emitter

Collector

Base

69. Semi-conductor germanium and silicon are

Pentavalent

Divalent

Trivalent

Tetravalent

70. Zener breakdown in a semiconductor diode occurs when

Forward current exceeds certain value

Potential barrier is reduced to zero

Forward bias exceeds certain value

Reverse bias exceeds certain value

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

Free electrons

Tightly bound electrons

Valence electrons

None of these

72. The least doped region in a transistor is

Base

Emitter

Collector

Either emitter or collector

73. Identify the correct statement about minority carriers

Holes in n-type and p-type

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

Free electrons in n-type and p-type

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

74. 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

75. When the output of OR gate is 1

If either or both inputs are 1

Only if both inputs are 1

If both inputs are zero

If either input is zero

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

Resistance of both decreases

Resistance of copper decreases while that of germanium increases

Resistance of both increases

Resistance of copper increases while that of germanium decreases

77. Symbol represents

XNOR gate

NOT gate

NAND gate

NOR gate

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

1 cm

1 mm

10¯⁶ cm

10¯¹² cm

79. 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

80. 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

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

Boron

Aluminum

Gold

Phosphorus

82. 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 bad is empty

Valence band is partially filled with electrons

83. The least doped region in a transistor is

Collector

Base

Emitter

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

4.9

9.8

85. Young’s modulus for copper is

110 Nm¯²

None of these

70 x 10 Nm¯²

91 x 10 Nm¯²

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

Extra electrons

Protons

Missing electrons

Neutrons

87. 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

88. 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

89. NAND gate is

A basic gate

A basic universal gate

A universal gate

Not a universal gate

90. In half wave rectification

Current flows in one directions

Current flows in pulses

None of these

Only half cycle is used

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

Extrinsic

n-type

Intrinsic

p-type

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

Ohms

Mega ohms

Kilo ohms

Several mega ohms

93. 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

94. Radio waves of constant amplitude can be generated with

Oscillator

Filter

Rectifier

FET

95. The thickness of the base is equal to

Thickness of collector

Mean of thickness of emitter and collector

Thickness of emitter

Very small as compared to the thickness of emitter and collector

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

n-type

p-type

Insulator

Superconductor

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

Electrons move from base to collector

Holes move from emitter to base

Holes move from base to emitter

98. In a n-p-n transistor:

Holes move from emitter to base

Negative charge moves from emitter to base

Holes move from base to collector

Negative charge moves from collector to base

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

N-type semiconductor

None of these

P-type semiconductor

N-type conductor

100. 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 LOW

At least one input is HIGH

101. 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

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

NOT gate

OR gate

XOR gate

AND gate

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

In reverse bias

None of these

To A.C.

In forward bias

104. 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

105. 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

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

None of these

Emitter

Collector

Base

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

None of these

Tensile stress

Shear stress

Compress ional stress

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

Infinity

Zero

Almost zero

None of these

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

A rectifier

Filtering circuit

Converter

An amplifier

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

None of these

Oscillator

Detector

Rectifier

111. A substance which have empty conduction band is called

Semiconductor

Insulator

None of these

Conductor

112. A n-p-n transistor conducts when

Both collector and emitter are positive with respect to the base

Both collector and emitter are negative with respect to the base

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

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

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

4.9

9.8

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

Using a transistor

Suppressing the harmonics in A.C voltage

Using a Coolidge tube

Suppressing half wave of A.C supply by using diode

115. Non-inverting amplifier circuits have

None of these

A very low input impedance

A low output impedance

A very high input impedance

116. 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

Potential barrier in depletion layer increases

Diode is reverse biased

Diode is forward based

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

n-type

Intrinsic

p-type

Extrinsic

118. At absolute zero, Si acts as

Non-metal

None of these

Metal

Insulator

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

Decreased by reverse biasing

Is independent of voltage

Increased by reverse biasing

Increased by forward biasing

120. 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

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

Antimony

Arsenic

Phosphorus

Aluminum

122. 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

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

Increases

Decreases and then increases

Remains unchanged

Decreases

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

n-type conductor

n-type semiconductor

p-type semiconductor

p-type conductor

125. Photodiode is used for

Light display

Emission of light

Detection of light

None of these

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

127. In forward bias the width of potential barrier

No effect

Remains same

Decreases

Increases

128. Arsenic, antimony or phosphorus are impurities of

n-type

p-type

None of these

may be p-type or n-type

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

Transistor

Amplifier

Rectifier

Diode

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

Neutrons

Extra electrons

Missing electrons

Protons

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

0.67 V

0.5 V

0.7 V

0.9 V

132. A transistor consists of

One PN-junction

Two PN-junctions

Three PN-junctions

Four PN-junctions

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

Neutrons

None of these

Holes

Electrons

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

Increase the minority carrier current

Lowers the potential barrier

Increase the majority carrier current

Raises the potential barrier

135. N-type crystal is

Neutral

None of these

Negative charged

Positively charged

136. The ratio β shows the

Current gain

Voltage gain

None of these

Input resistance

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

Forward bias

Doping density

Diode design

Temperature

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

Young’s modulus

None of these

Modulus of electricity

Bulk’s modulus

139. Application of photodiode is/are

Logic gates

Detection of visible and invisible radiations

None of these

Automatic switching

140. The critical temperature for mercury is

1.18 K

7.2 K

3.72 K

4.2 K

141. In insulators

Conduction band is filled with electrons and valence band is empty

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

142. The working of transistor as amplifier is similar to

Step up transformer

Three diodes in common

Triode vacuum tube

Step down transformer

143. 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

Zero biased

None of these

Reversed biased

Forward biased

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

Crystal lattice

All of these

Unit cell

Ore

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

P-type material

Oscillator

Amplifier

Rectifier

146. Light emitting diode work when it is

Reverse biased

None of these

Forward biases

Both

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

Less than one

Greater than one

Equal to one

Of zero

148. 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

149. 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

150. When NPN transistor is used as an amplifier

Electrons move from emitter to base

Holes move from base to emitter

Electrons move from base to emitter

Electrons move from collector to base

151. Diode can work as

Rectifier

Oscillator

Modulator

Multivibrator

152. 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

Hidden energy states

Band levels

None of these

153. The forward resistance of the diode is

Ohms

None of these

Few ohms

Many ohms

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

Collector

Emitter

Base

Any of above

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

None of these

Hundreds

Man hundred

Thousands

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

On switch

Capacitor

Inductor

Off switch

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

Electromagnetic Waves

x-rays

Gamma Rays

Transverse Waves

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

INVERTER gate

Comparator

AND gate

OR gate

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

AND gates and NOT gates

OR gates only

Or gates and NOT gates

AND gates, OR gates, and NOT gates

160. 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

Virtual input

Output

161. 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

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

Semiconductors

Conductors

Insulators

Superconductors

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

Greater than emitter current

Slightly less than emitter current

Any of above

Equal to emitter current

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

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

It has high resistance to the current flow when reverse biased

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

None of these

Microsecond

Millisecond

Nanosecond

166. The operation of a transistor requires

That the collector be heated

That the emitter be heated

That the base be heated

None of these

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

Diffusion region

None of these

Charged region

Depletion region

168. The number of junctions in the PNP transistor are

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

Remains unchanged

Decreases

Increases

Decreases and then increases

170. Transistor can be used as

Filter

Full wave rectifier

Half wave rectifier

Amplifier

171. LDR means:

Low degree resistor

Low degree radiations

Light dependent resistance

None of these

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

It offers a very low output resistance

None of these

It offers a very low open loop gain all of above

It offers a very high inputs resistance to the input current

173. In p-type semiconductor

Major carrier is mobile negative ions

Major carrier is mobile holes

Major current carrier is electrons

The number of mobile holes exceeds the number of acceptors

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

Shear modulus

Young’s modulus

Bulk modulus

None of these

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

Conductor

Insulator

Alloy

Semiconductor

176. Depletion region of a junction is formed

Under reverse bias

During the manufacturing process

Under forward bias

When temperature varies

177. In Germanium crystal, impurity donor elements have valiancy

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Malik TahirLast Updated: May 26, 2025

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