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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. In Germanium crystal, impurity donor elements have valiancy

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

Amplification

Magnification

All of these

Rectification

3. 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

4. In a n-p-n transistor:

Holes move from base to collector

Negative charge moves from collector to base

Negative charge moves from emitter to base

Holes move from emitter to base

5. In semiconductors at a room temperature

The valence band is completely filled

The conduction band is completely empty

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

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

6. The operation of a transistor requires

That the emitter be heated

That the collector be heated

That the base be heated

None of these

7. The energy band gap is maximum in

Insulators

Semiconductors

Metals

Superconductors

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

Arsenic

Indium

Phosphorus

Antimony

9. The critical temperature for mercury is

4.2 K

1.18 K

3.72 K

7.2 K

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

0.7 V

0.5 V

0.9 V

0.67 V

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

Majority carriers

Blockers

Dual carriers

Minority carriers

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

None of these

Young’s modulus

Bulk’s modulus

Modulus of electricity

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

any of above

mix

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

Aluminum

Boron

Gallium

All of above

15. 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

None of these

It offers a very low output resistance

16. Light emitting diode work when it is

Forward biases

Reverse biased

Both

None of these

17. In Germanium crystal, impurity donor elements have valiancy

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

Resistance of both decreases

Resistance of copper increases while that of germanium decreases

Resistance of copper decreases while that of germanium increases

Resistance of both increases

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

Electrons and holes

Protons and electrons

Electrons and protons

Holes and electrons

20. 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 few electrons

Large number of holes and electrons

21. Non-inverting amplifier circuits have

A low output impedance

A very high input impedance

None of these

A very low input impedance

22. Photovoltaic cell produces electrical energy from

None of these

Chemical energy

Light energy

Heat energy

23. 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 holes

Major current carriers are mobile negative ions

24. 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

None of these

Diode is neutralized

25. The energy band gap is maximum in

Insulators

Metals

Semiconductors

Superconductors

26. The forward resistance of the diode is

Few ohms

Many ohms

None of these

Ohms

27. n-type semiconductor if formed

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

From pure Si crystal

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

From pure Ge crystal

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

Logic gates

Oscillator

Amplifier

Filter

29. When the output of OR gate is 1

If both inputs are zero

If either or both inputs are 1

Only if both inputs are 1

If either input is zero

30. Radio waves of constant amplitude can be generated with

Oscillator

FET

Rectifier

Filter

31. Semi-conductor germanium and silicon are

Pentavalent

Divalent

Trivalent

Tetravalent

32. Which one is reverse-biased?

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

Almost negligible

Very low

Very high

Zero

34. The ratio β represents

35. Depletion region of a junction is formed

Under reverse bias

During the manufacturing process

Under forward bias

When temperature varies

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

Neutrons

Protons

Extra electrons

Missing electrons

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

Electrons

None of these

Neutrons

Holes

38. In half wave rectification

None of these

Current flows in one directions

Only half cycle is used

Current flows in pulses

39. To use a transistor as an amplifier

Both junctions are reverse biased

Both junctions are forward biased

No bias voltages are required

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

40. The ratio β shows the

Voltage gain

None of these

Current gain

Input resistance

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

Intrinsic

p-type

n-type

Extrinsic

42. 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

Collector

Emitter

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

Non-inverting voltage at output

Virtual input

Reference voltage on the other

Output

44. Which one is forward bias?

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

Decreases and then increases

Decreases

Increases

Remains unchanged

46. 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

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

Mega ohms

Ohms

Several mega ohms

Kilo ohms

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

Both are at the same potential

Both are at the high potential

Non-inverting terminal is at high potential

Inverting terminal is at high potential

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

None of these

Hundreds

Thousands

Man hundred

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

p-type semiconductor

n-type semiconductor

p-type conductor

n-type conductor

51. The thickness of the base is equal to

Thickness of emitter

Thickness of collector

Very small as compared to the thickness of emitter and collector

Mean of thickness of emitter and collector

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

Less than one

Greater than one

Equal to one

Of zero

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

Constant amplitude

Variable amplitude

Unit amplitude

Zero amplitude

54. The working of transistor as amplifier is similar to

Three diodes in common

Step up transformer

Step down transformer

Triode vacuum tube

55. At absolute zero, Si acts as

Insulator

Metal

Non-metal

None of these

56. In p-type semiconductor

Major carrier is mobile holes

The number of mobile holes exceeds the number of acceptors

Major current carrier is electrons

Major carrier is mobile negative ions

57. In a semiconductor, the mobility of holes is

Less than electrons

Equal to electrons

Greater than electrons

None

58. With negative feedback, the returning signal:

Aids the input signal

Opposes the input signal

Is proportional to differential voltage gain

Is proportional to output current

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

p-type

n-type

Superconductor

Insulator

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

A rectifier

An amplifier

Converter

Filtering circuit

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

Computers

Electric motors

Electric generations

Transformers

62. 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 to base

Electrons move from base to collector

63. Depletion layer consists of

Immobile ions

Mobile ions

Electrons

Protons

64. An OP-AMPs can amplify

Both A.C. & D.C.

A.C.

D.C.

None of these

65. In insulators

Conduction band is empty and valence band is filled with electrons

Conduction band is partially filled with electrons

Conduction band is filled with electrons and valence band is empty

Valence band is partially filled with electrons

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

NOT gate

XOR gate

OR gate

AND gate

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

Holes

Neutrons

Protons

Electrons

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

N-type conductor

P-type semiconductor

None of these

N-type semiconductor

69. At absolute zero, Si acts as

None of these

Insulator

Non-metal

Metal

70. 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

71. Application of photodiode is/are

None of these

Detection of visible and invisible radiations

Logic gates

Automatic switching

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

Using a transistor

Suppressing half wave of A.C supply by using diode

Using a Coolidge tube

Suppressing the harmonics in A.C voltage

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

All inputs are LOW

At least one input is LOW

At least one input is HIGH

All inputs are HIGH

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

N-type material

Super conductor

Semiconductor

P-type material

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

Increases slowly

Remain fixed

Suddenly increases

Decreases slowly

76. Photodiode is used for

None of these

Emission of light

Light display

Detection of light

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

None of these

Damaged

Works efficiently

Require more current

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

Amplifier

Diode

Rectifier

Transistor

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

None of these

Zero

Infinity

Almost zero

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

Amplifier

Rectifier

P-type material

Oscillator

81. In forward bias the width of potential barrier

Remains same

No effect

Increases

Decreases

82. 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

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

Any of above

Emitter

Collector

Base

84. 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

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

Force

Strain

None of these

Stress

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

Charged region

Depletion region

Diffusion region

None of these

87. Polythene, potystrene and nylon are examples of

Glassy solids

Amorphous solids

Crystalline solids

Polymeric solids

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

Doping density

Temperature

Diode design

Forward bias

89. In a n-p-n transistor:

Holes move from base to collector

Negative charge moves from collector to base

Negative charge moves from emitter to base

Holes move from emitter to base

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

Infinity

Wide

Zero

Narrow

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

Extra electrons

Protons

Neutrons

Missing electrons

92. Young’s modulus for copper is

70 x 10 Nm¯²

110 Nm¯²

None of these

91 x 10 Nm¯²

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

Transverse Waves

x-rays

Electromagnetic Waves

Gamma Rays

94. 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

Collector

Base

Emitter

95. The logic gate that will have HIGH or “1” at its output when any one of its input if HIGH is a(n):

OR gate

NOR gate

AND gate

NOT gate

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

Common emitter configuration

Common base configuration

Common collector configuration

None of these

97. N-type crystal is

Negative charged

Neutral

None of these

Positively charged

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

Can be any of the above three

Base

Emitter

Collector

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

Antimony

Arsenic

Aluminum

Phosphorus

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

Semiconductor

Conductor

Insulator

Alloy

101. A transistor consists of

Four PN-junctions

Two PN-junctions

Three PN-junctions

One PN-junction

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

Decreased by reverse biasing

Is independent of voltage

Increased by forward biasing

Increased by reverse biasing

103. A diode as a rectifier converts:

High voltage to low voltage

Low voltage to high voltage

A.C. into D.C.

D.C. into A.C.

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

Increase the majority carrier current

Raises the potential barrier

Lowers the potential barrier

Increase the minority carrier current

105. Which is normal used of transistor?

Rectifier

Diode

P-type material

Switching device

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

Diffusion of charges

Drift of charges

Both drift and diffusion of charges

Depends upon the nature of material

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

Decreased by reverse biasing

Increased by forward biasing

Is independent of voltage

Increased by reverse biasing

108. The least doped region in a transistor is

Emitter

Collector

Base

Either emitter or collector

109. The number of junctions in the PNP transistor are

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

Rectifier

Oscillator

None of these

Detector

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

None of these

Insulator

Superconductor

Semiconductor

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

Slightly less than emitter current

Equal to emitter current

Greater than emitter current

Any of above

113. A NAND gate has:

LOW inputs and a HIGH output

None of these

HIGH inputs and a HIGH output

LOW inputs and a LOW output

114. Reverse bias applied on a junction diode

Lowers the potential barrier

Raises the potential barrier

Increases the majority carrier current

Increase the minority carrier current

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

Millisecond

Microsecond

Nanosecond

None of these

116. Acceptor and donor impurities donate

n-carriers only

p-carriers only

p-carriers and n-carriers respectively

n-carriers and p-carriers respectively

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

Capacitor is used

Resistor is used

Solvent is used

None of these

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

119. Identify the correct statement about minority carriers

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

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

120. LDR means:

None of these

Low degree radiations

Low degree resistor

Light dependent resistance

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

10¯⁶ cm

1 mm

10¯¹² cm

1 cm

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

Arsenic

Phosphorus

Aluminum

Antimony

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

None of these

Low

Zero

High

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

9.8

4.9

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

Holes move from emitter to base

Holes move from emitter be base

Holes move from base to emitter

Electrons move from base to collector

127. 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

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

Decreases

First A and B

Increases

Remains constant

129. Zener breakdown in a semiconductor diode occurs when

Reverse bias exceeds certain value

Forward current exceeds certain value

Potential barrier is reduced to zero

Forward bias exceeds certain value

130. In between two consecutive permissible energy bands, there is a range of energy states which cannot be occupied by electrons. These are called

Forbidden energy states

Band levels

None of these

Hidden energy states

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

Enable it to Telerate higher voltage

Increase its life

Increases its electrical conductivity

Increase its electrical resistivity

132. In insulators

Conduction band is empty and valence band is filled with electrons

Valence band is partially filled with electrons

Conduction band is partially filled with electrons

Conduction band is filled with electrons and valence bad is empty

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

All of these

Ore

Crystal lattice

Unit cell

134. 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 remains same

Number of electrons and holes increases equally

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

Extrinsic

n-type

Intrinsic

p-type

136. 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

Increase its life

Increase its electrical conductivity

137. Which logic gate is represented by following diagram?

NOR

AND

EOR

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

AND gate

OR gate

NAND gate

NOT gate

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

The photo diodes

The switch

The light emitting diode

Solar cells

140. The least doped region in a transistor is

Base

Emitter

Collector

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

Base

None of these

Emitter

Collector

142. 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 at negative potential as the base

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

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

n-type conductor

p-type conductor

p-type semiconductor

n-type semiconductor

144. Transistor can be used as

Half wave rectifier

Full wave rectifier

Amplifier

Filter

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

OR gates

NAND gates

AND gates

NOT gates

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

Stress

Force

Strain

None of these

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

Remains unchanged

Increases

Decreases

Decreases and then increases

148. 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

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

Large number of holes and few electrons

Large number of free electrons and few holes

Large number of holes and electrons

Equal number of free electrons and holes

150. In a P-type semiconductor

Major current carriers are mobile negative ions

Major current carriers are mobile holes

Major current carriers are electrons

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

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

Gold

Phosphorus

Boron

Aluminum

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

Shear modulus

Bulk modulus

None of these

Young’s modulus

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

Shear stress

None of these

Compress ional stress

Tensile stress

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

9.8

4.9

155. In the transistor schematic symbol, the arrow

Is locate on the collector

Point from north to south

Is located on the emitter

Is located on the base

156. Symbol represents

XNOR gate

NOR gate

NAND gate

NOT gate

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

Logic gates

Filter

Oscillator

Amplifier

158. Diode can work as

Oscillator

Multivibrator

Rectifier

Modulator

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

Comparator

INVERTER gate

AND gate

OR gate

160. p-type crystal of a p-n junction diode is connected to a positive terminal of battery and n-type crystal connected to negative terminal of battery

Potential barrier in depletion layer increases

Diode is reverse biased

Diode is forward based

Potential barrier in depletion layer remains unchanged

161. When NPN transistor is used as an amplifier

Holes move from base to emitter

Electrons move from base to emitter

Electrons move from emitter to base

Electrons move from collector to base

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

Superconductors

Conductors

Semiconductors

Insulators

163. Arsenic, antimony or phosphorus are impurities of

n-type

may be p-type or n-type

p-type

None of these

164. In semiconductors at a room temperature

The valence band is completely filled

The conduction band is completely empty

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

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

165. If p-type material of the PN-junction is connected with positive terminal of the battery and n-type material with negative terminal of the battery, it is said to be

None of these

Forward biased

Reversed biased

Zero biased

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

Boron

All of these

Aluminum

Gallium

167. NAND gate is

A basic gate

A basic universal gate

Not a universal gate

A universal gate

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

Free electrons

Valence electrons

Tightly bound electrons

None of these

169. The positive sign of gain indicates that

May be in phase or not

None of these

Input and out signals are in phase

Input and out signals are not in phase

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

On switch

Capacitor

Off switch

Inductor

171. A substance which have empty conduction band is called

Semiconductor

None of these

Conductor

Insulator

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

Protons

Neutrons

Missing of electrons

Extra electrons

173. 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

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

Each of them decreases

Copper increases and germanium decreases

Copper decreases and germanium increases

Each of them increases

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

p-type semiconductor

n-type semiconductor

p-type conductor

n-type conductor

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

In reverse bias

In forward bias

None of these

To A.C.

177. 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 increases

Each of them decreases

Copper increases and germanium decreases

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Malik TahirLast Updated: May 26, 2025

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