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

Insulator

None of these

Superconductor

Semiconductor

2. In insulators

Valence band is partially filled with electrons

Conduction band is filled with electrons and valence bad is empty

Conduction band is empty and valence band is filled with electrons

Conduction band is partially filled with electrons

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

Gamma Rays

Electromagnetic Waves

x-rays

Transverse Waves

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

Large number of holes and few electrons

Equal number of free electrons and holes

Large number of holes and electrons

Large number of free electrons and few holes

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

Doping density

Temperature

Forward bias

Diode design

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

n-type conductor

p-type semiconductor

p-type conductor

n-type semiconductor

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

Emitter

Base

Can be any of the above three

Collector

8. At absolute zero, Si acts as

Insulator

Metal

Non-metal

None of these

9. The energy band gap is maximum in

Metals

Superconductors

Insulators

Semiconductors

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

Antimony

Arsenic

Aluminum

Phosphorus

11. Which logic gate is represented by following diagram?

AND

NOR

EOR

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

Increase the minority carrier current

Increase the majority carrier current

Lowers the potential barrier

Raises the potential barrier

13. The ratio β shows the

Input resistance

Voltage gain

None of these

Current gain

14. 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

15. 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

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

Kilo ohms

Mega ohms

Several mega ohms

Ohms

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

4.9

9.8

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

Decreases and then increases

Remains unchanged

Decreases

Increases

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

Semiconductor

Alloy

Conductor

Insulator

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

All of above

Aluminum

Gallium

Boron

21. Acceptor and donor impurities donate

p-carriers only

n-carriers only

p-carriers and n-carriers respectively

n-carriers and p-carriers respectively

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

Compress ional stress

None of these

Tensile stress

Shear stress

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

Emitter

Base

Collector

Can be any of the above three

24. The least doped region in a transistor is

Emitter

Base

Collector

Either emitter or collector

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

Microsecond

None of these

Millisecond

Nanosecond

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

Copper increases and germanium decreases

Copper decreases and germanium increases

Each of them increases

Each of them decreases

27. The least doped region in a transistor is

Collector

Base

Emitter

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

Crystal lattice

Unit cell

Ore

All of these

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

Amplifier

Logic gates

Filter

Oscillator

30. In a P-type semiconductor

Major current carriers are electrons

Major current carriers are mobile holes

Major current carriers are mobile negative ions

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

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

Resistance of both increases

Resistance of copper increases while that of germanium decreases

Resistance of both decreases

Resistance of copper decreases while that of germanium increases

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

Require more current

Damaged

Works efficiently

None of these

33. When n-type of semiconductor is heated,

Number of electrons increases while that of holes decreases

Number of electrons and holes remains same

Number of electrons and holes increases equally

Number of holes increases while that of holes decreases

34. Application of photodiode is/are

Automatic switching

Logic gates

Detection of visible and invisible radiations

None of these

35. Arsenic, antimony or phosphorus are impurities of

None of these

p-type

may be p-type or n-type

n-type

36. 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 neutralized

Diode is reverse biased

None of these

37. The operation of a transistor requires

That the base be heated

That the collector be heated

None of these

That the emitter be heated

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

NAND gate

OR gate

AND gate

NOT gate

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

Zero

Infinity

Narrow

Wide

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

AND gates

NOT gates

NAND gates

OR gates

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

Electrons and holes

Holes and electrons

Protons and electrons

Electrons and protons

42. NAND gate is

A basic universal gate

A basic gate

A universal gate

Not a universal gate

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

None of these

Valence electrons

Free electrons

Tightly bound electrons

44. In Germanium crystal, impurity donor elements have valiancy

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

Increase its life

Increases its electrical conductivity

Enable it to Telerate higher voltage

Increase its electrical resistivity

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

1 mm

10¯¹² cm

10¯⁶ cm

1 cm

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

Almost zero

Zero

None of these

Infinity

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

Protons

Neutrons

Electrons

Holes

49. Semi-conductor germanium and silicon are

Trivalent

Tetravalent

Divalent

Pentavalent

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

4.9

9.8

51. The forward resistance of the diode is

Many ohms

None of these

Few ohms

Ohms

52. The critical temperature for mercury is

4.2 K

3.72 K

7.2 K

1.18 K

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

P-type material

Super conductor

N-type material

Semiconductor

54. Light emitting diode work when it is

Reverse biased

Both

Forward biases

None of these

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

None of these

Stress

Force

Strain

56. Polythene, potystrene and nylon are examples of

Crystalline solids

Glassy solids

Amorphous solids

Polymeric solids

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

Drift of charges

Diffusion of charges

Depends upon the nature of material

Both drift and diffusion of charges

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

Remains unchanged

Decreases

Decreases and then increases

Increases

59. Radio waves of constant amplitude can be generated with

FET

Filter

Rectifier

Oscillator

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

The switch

Solar cells

The photo diodes

The light emitting diode

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

Aluminum

Phosphorus

Gold

Boron

62. When NPN transistor is used as an amplifier

Holes move from base to emitter

Electrons move from collector to base

Electrons move from emitter to base

Electrons move from base to emitter

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

Electric field is maximum

Potential is zero

Potential is maximum

Electric field is zero

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

65. 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

66. Non-inverting amplifier circuits have

None of these

A very high input impedance

A low output impedance

A very low input impedance

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

Strain

None of these

Stress

Force

68. The thickness of the base is equal to

Mean of thickness of emitter and collector

Thickness of emitter

Very small as compared to the thickness of emitter and collector

Thickness of collector

69. Symbol represents

XNOR gate

NOR gate

NAND gate

NOT gate

70. 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

NOR gate

AND gate

OR gate

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

OR gates only

AND gates, OR gates, and NOT gates

AND gates and NOT gates

Or gates and NOT gates

72. In Germanium crystal, impurity donor elements have valiancy

73. An OP-AMPs can amplify

None of these

A.C.

Both A.C. & D.C.

D.C.

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

Modulus of electricity

Bulk’s modulus

Young’s modulus

None of these

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

n-type

Intrinsic

Extrinsic

p-type

76. A n-p-n transistor conducts when

Collector is positive and emitter is at negative potential as 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

Both collector and emitter are positive with respect to the base

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

Common emitter configuration

Common base configuration

Common collector configuration

None of these

78. Photodiode is used for

Detection of light

Emission of light

None of these

Light display

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

Missing electrons

Protons

Extra electrons

Neutrons

80. 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

81. LDR means:

None of these

Low degree radiations

Low degree resistor

Light dependent resistance

82. In a n-p-n transistor:

Holes move from base to collector

Negative charge moves from emitter to base

Negative charge moves from collector to base

Holes move from emitter to base

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

Resistor is used

Solvent is used

Capacitor is used

None of these

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

Electric motors

Electric generations

Computers

Transformers

85. Zener breakdown in a semiconductor diode occurs when

Potential barrier is reduced to zero

Reverse bias exceeds certain value

Forward bias exceeds certain value

Forward current exceeds certain value

86. In the transistor schematic symbol, the arrow

Is locate on the collector

Is located on the base

Point from north to south

Is located on the emitter

87. 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

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

Base

Emitter

Collector

Any of above

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

Electrons move from base to collector

Holes move from base to emitter

Holes move from emitter to base

Holes move from emitter be base

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

Increases

Remains constant

First A and B

Decreases

91. The positive sign of gain indicates that

Input and out signals are in phase

Input and out signals are not in phase

May be in phase or not

None of these

92. 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

None of these

Band levels

Hidden energy states

93. With negative feedback, the returning signal:

Opposes the input signal

Is proportional to output current

Is proportional to differential voltage gain

Aids the input signal

94. The working of transistor as amplifier is similar to

Step up transformer

Step down transformer

Three diodes in common

Triode vacuum tube

95. A pieced 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

96. A transistor consists of

Three PN-junctions

Two PN-junctions

Four PN-junctions

One PN-junction

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

Semiconductors

Superconductors

Insulators

Conductors

98. Depletion region of a junction is formed

Under reverse bias

Under forward bias

When temperature varies

During the manufacturing process

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

90° Phase shift

No Phase shift

120° Phase shift

180° Phase shift

100. Photovoltaic cell produces electrical energy from

Light energy

Heat energy

None of these

Chemical energy

101. 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):

AND

NOR

NAND

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

Greater than emitter current

Any of above

Equal to emitter current

Slightly less than emitter current

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

Virtual input

Reference voltage on the other

Output

Non-inverting voltage at output

104. At absolute zero, Si acts as

Non-metal

Insulator

Metal

None of these

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

Aluminum

Phosphorus

Arsenic

Antimony

106. 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

Non-inverting terminal is at high potential

Both are at the same potential

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

Base

Collector

Emitter

Any of the above depending on nature of transistor

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

Unit amplitude

Variable amplitude

Constant amplitude

Zero amplitude

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

None of these

Rectifier

Detector

Oscillator

110. Depletion layer consists of

Electrons

Protons

Immobile ions

Mobile ions

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

All of these

Boron

Gallium

Aluminum

112. In forward bias the width of potential barrier

No effect

Decreases

Increases

Remains same

113. A substance which have empty conduction band is called

Conductor

None of these

Semiconductor

Insulator

114. 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 electrons

Major current carriers are mobile negative ions

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

Insulator

Superconductor

n-type

p-type

116. In p-type semiconductor

The number of mobile holes exceeds the number of acceptors

Major current carrier is electrons

Major carrier is mobile negative ions

Major carrier is mobile holes

117. In half wave rectification

Current flows in pulses

Only half cycle is used

None of these

Current flows in one directions

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

Filter

Logic gates

Amplifier

Oscillator

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

Potential is maximum

Potential is zero

Electric field is maximum

Electric field is zero

120. Which one is reverse-biased?

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

Emitter

Base

None of these

Collector

122. Transistor can be used as

Amplifier

Filter

Half wave rectifier

Full wave rectifier

123. 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

124. N-type crystal is

None of these

Negative charged

Neutral

Positively charged

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

Amplifier

P-type material

Rectifier

Oscillator

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

Very high

Zero

Very low

Almost negligible

127. The ratio β represents

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

Rectifier

Diode

Transistor

Amplifier

129. Which one is forward bias?

130. In a PN junction

Undetermined

P and N both are at same potential

High potential at N side and low potential at P side

High potential at P side and low potential at N side

131. Young’s modulus for copper is

110 Nm¯²

70 x 10 Nm¯²

91 x 10 Nm¯²

None of these

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

Suddenly increases

Decreases slowly

Remain fixed

Increases slowly

133. Which is normal used of transistor?

Switching device

Diode

P-type material

Rectifier

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

Holes move from base to emitter

Electrons move from base to collector

Holes move from emitter to base

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

Equal to one

Greater than one

Of zero

Less than one

136. 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.

137. 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

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

Antimony

Arsenic

Indium

Phosphorus

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

Extrinsic

Intrinsic

p-type

n-type

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

NOT gate

AND gate

XOR gate

OR gate

141. 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

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

0.5 V

0.67 V

0.7 V

0.9 V

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

any of above

mix

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

Amplification

All of these

Rectification

Magnification

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

Off switch

Inductor

Capacitor

On switch

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

An amplifier

Converter

Filtering circuit

A rectifier

147. In a n-p-n transistor:

Negative charge moves from collector to base

Holes move from emitter to base

Holes move from base to collector

Negative charge moves from emitter to base

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

Low

High

None of these

Zero

149. The number of junctions in the PNP transistor are

150. 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

Reversed biased

Zero biased

None of these

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

Missing of electrons

Protons

Extra electrons

Neutrons

152. A NAND gate has:

LOW inputs and a LOW output

None of these

HIGH inputs and a HIGH output

LOW inputs and a HIGH output

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

Minority carriers

Majority carriers

Dual carriers

Blockers

154. 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

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

Increase its life

Increase its electrical resistivity

Enable it to Telerate higher voltage

Increase its electrical conductivity

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

It has low resistance to the current flow when forward biased

It has high resistance to the current flow when reverse biased

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

Its conductivity increases with rise of temperature

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

Equal number of free electrons and holes

Large number of free electrons and few holes

Large number of holes and electrons

Large number of holes and few electrons

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

p-type conductor

p-type semiconductor

n-type conductor

n-type semiconductor

159. In insulators

Conduction band is partially filled with electrons

Valence band is partially filled with electrons

Conduction band is filled with electrons and valence band is empty

Conduction band is empty and valence band is filled with electrons

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

None of these

Bulk modulus

Young’s modulus

Shear modulus

161. Identify the correct statement about minority carriers

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

Holes in n-type and p-type

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

Neutrons

None of these

Electrons

Holes

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

Depletion region

Charged region

None of these

Diffusion region

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

Thousands

Man hundred

None of these

Hundreds

165. Reverse bias applied on a junction diode

Increases the majority carrier current

Increase the minority carrier current

Lowers the potential barrier

Raises the potential barrier

166. A diode as a rectifier converts:

A.C. into D.C.

Low voltage to high voltage

D.C. into A.C.

High voltage to low voltage

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

P-type semiconductor

None of these

N-type conductor

N-type semiconductor

168. In a semiconductor, the mobility of holes is

Greater than electrons

None

Equal to electrons

Less than electrons

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

None of these

To A.C.

In forward bias

In reverse bias

170. The energy band gap is maximum in

Metals

Semiconductors

Insulators

Superconductors

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

Extra electrons

Neutrons

Missing electrons

Protons

172. Diode can work as

Modulator

Oscillator

Rectifier

Multivibrator

173. 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

Diode is forward based

Potential barrier in depletion layer remains unchanged

174. 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

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

AND gate

INVERTER gate

Comparator

OR gate

176. 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

177. 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

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Malik TahirLast Updated: May 26, 2025

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