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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. N-type crystal is

Neutral

None of these

Negative charged

Positively charged

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

0.67 V

0.5 V

0.7 V

0.9 V

3. Reverse bias applied on a junction diode

Increases the majority carrier current

Raises the potential barrier

Increase the minority carrier current

Lowers the potential barrier

4. Depletion region of a junction is formed

During the manufacturing process

Under reverse bias

Under forward bias

When temperature varies

5. Non-inverting amplifier circuits have

None of these

A very high input impedance

A low output impedance

A very low input impedance

6. When NPN transistor is used as an amplifier

Holes move from base to emitter

Electrons move from collector to base

Electrons move from base to emitter

Electrons move from emitter to base

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

Protons and electrons

Electrons and holes

Holes and electrons

Electrons and protons

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

Increases

Decreases

Remains unchanged

Decreases and then increases

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

OR gates

AND gates

NOT gates

NAND gates

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

Arsenic

Antimony

Phosphorus

Indium

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

Collector

Base

Can be any of the above three

Emitter

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

10¯¹² cm

10¯⁶ cm

1 cm

1 mm

13. Zener breakdown in a semiconductor diode occurs when

Forward current exceeds certain value

Forward bias exceeds certain value

Reverse bias exceeds certain value

Potential barrier is reduced to zero

14. In a P-type semiconductor

Major current carriers are electrons

Major current carriers are mobile negative ions

Major current carriers are mobile holes

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

15. 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

16. Semi-conductor germanium and silicon are

Pentavalent

Divalent

Trivalent

Tetravalent

17. 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 valence band is completely filled

The conduction band is completely empty

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

Logic gates

Oscillator

Amplifier

Filter

19. Photodiode is used for

Light display

None of these

Emission of light

Detection of light

20. 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

21. 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

Potential barrier in depletion layer remains unchanged

Diode is forward based

Diode is reverse biased

22. The energy band gap is maximum in

Insulators

Semiconductors

Superconductors

Metals

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

Aluminum

Antimony

Arsenic

Phosphorus

24. 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

25. When n-type of semiconductor is heated,

Number of electrons and holes increases equally

Number of electrons and holes remains same

Number of holes increases while that of holes decreases

Number of electrons increases while that of holes decreases

26. An OP-AMPs can amplify

None of these

D.C.

A.C.

Both A.C. & D.C.

27. Acceptor and donor impurities donate

p-carriers only

n-carriers only

n-carriers and p-carriers respectively

p-carriers and n-carriers respectively

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

Protons

Holes

Electrons

Neutrons

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

Almost negligible

Very high

Very low

Zero

30. The operation of a transistor requires

That the emitter be heated

That the base be heated

That the collector be heated

None of these

31. The positive sign of gain indicates that

May be in phase or not

Input and out signals are in phase

None of these

Input and out signals are not in phase

32. Radio waves of constant amplitude can be generated with

Filter

Oscillator

FET

Rectifier

33. A transistor consists of

Four PN-junctions

Two PN-junctions

One PN-junction

Three PN-junctions

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

Conductor

Semiconductor

Alloy

Insulator

35. 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

36. In a n-p-n transistor:

Negative charge moves from emitter to base

Negative charge moves from collector to base

Holes move from base to collector

Holes move from emitter to base

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

In reverse bias

None of these

In forward bias

To A.C.

38. In a P-type semiconductor

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

Major current carriers are electrons

Major current carriers are mobile negative ions

Major current carriers are mobile holes

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

All of these

Aluminum

Gallium

Boron

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

INVERTER gate

OR gate

Comparator

AND gate

41. 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

Holes move from emitter to base

42. The working of transistor as amplifier is similar to

Step up transformer

Step down transformer

Three diodes in common

Triode vacuum tube

43. The ratio β shows the

None of these

Voltage gain

Input resistance

Current gain

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

Amplifier

Oscillator

Rectifier

P-type material

45. Depletion layer consists of

Protons

Mobile ions

Electrons

Immobile ions

46. NAND gate is

A universal gate

Not a universal gate

A basic universal gate

A basic gate

47. In insulators

Valence 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 bad is empty

Conduction band is partially filled with electrons

48. The number of junctions in the PNP transistor are

49. A NAND gate has:

HIGH inputs and a HIGH output

LOW inputs and a LOW output

None of these

LOW inputs and a HIGH output

50. In a PN junction

P and N both are at same potential

Undetermined

High potential at P side and low potential at N side

High potential at N side and low potential at P side

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

Dual carriers

Majority carriers

Minority carriers

Blockers

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

Large number of holes and electrons

Large number of holes and few electrons

Equal number of free electrons and holes

Large number of free electrons and few holes

53. LDR means:

Low degree radiations

Low degree resistor

Light dependent resistance

None of these

54. With negative feedback, the returning signal:

Aids the input signal

Is proportional to output current

Opposes the input signal

Is proportional to differential voltage gain

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

Magnification

Rectification

All of these

Amplification

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

Solar cells

The light emitting diode

The switch

The photo diodes

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

n-type

Intrinsic

Extrinsic

p-type

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

Compress ional stress

None of these

Shear stress

Tensile stress

59. To use a transistor as an amplifier

Both junctions are forward biased

Both junctions are reverse biased

No bias voltages are required

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

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

Copper increases and germanium decreases

Each of them increases

Copper decreases and germanium increases

Each of them decreases

61. Polythene, potystrene and nylon are examples of

Crystalline solids

Glassy solids

Polymeric solids

Amorphous solids

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

All inputs are HIGH

At least one input is HIGH

All inputs are LOW

At least one input is LOW

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

Potential is maximum

Electric field is zero

Potential is zero

Electric field is maximum

64. In p-type semiconductor

Major current carrier is electrons

The number of mobile holes exceeds the number of acceptors

Major carrier is mobile negative ions

Major carrier is mobile holes

65. At absolute zero, Si acts as

None of these

Metal

Insulator

Non-metal

66. In insulators

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

Conduction band is partially filled with electrons

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

Tightly bound electrons

Free electrons

Valence electrons

None of these

68. The least doped region in a transistor is

Emitter

Base

Collector

69. 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

Reversed biased

Forward biased

None of these

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

Both are at the high potential

Both are at the same potential

Inverting terminal is at high potential

Non-inverting terminal is at high potential

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

Young’s modulus

Bulk’s modulus

None of these

Modulus of electricity

72. 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

73. In the transistor schematic symbol, the arrow

Point from north to south

Is located on the emitter

Is locate on the collector

Is located on the base

74. In Germanium crystal, impurity donor elements have valiancy

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

Damaged

None of these

Require more current

Works efficiently

76. Arsenic, antimony or phosphorus are impurities of

p-type

None of these

may be p-type or n-type

n-type

77. 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

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

Capacitor

Inductor

On switch

Off switch

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

Increase its electrical conductivity

Increase its life

Enable it to Telerate higher voltage

Increase its electrical resistivity

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

Suddenly increases

Decreases slowly

Remain fixed

Increases slowly

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

Doping density

Forward bias

Diode design

Temperature

82. Which is normal used of transistor?

Switching device

P-type material

Rectifier

Diode

83. 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

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

Electric field is maximum

Potential is zero

Electric field is zero

Potential is maximum

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

p-type conductor

n-type conductor

n-type semiconductor

p-type semiconductor

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

Remains unchanged

Increases

Decreases and then increases

Decreases

87. 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

88. If positive end of battery is connected to p-side and negative end of battery is connected to n-side of diode then

Diode is neutralized

None of these

Diode is reverse biased

Diode is forward biased

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

Shear modulus

Bulk modulus

Young’s modulus

None of these

90. 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

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

Increased by reverse biasing

Is independent of voltage

Increased by forward biasing

Decreased by reverse biasing

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

Protons

Neutrons

Extra electrons

Missing of electrons

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

Aluminum

Boron

Phosphorus

Gold

94. In forward bias the width of potential barrier

No effect

Increases

Decreases

Remains same

95. 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

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

9.8

4.9

97. 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

Virtual input

Output

98. 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.

99. When the output of OR gate is 1

If either input is zero

Only if both inputs are 1

If both inputs are zero

If either or both inputs are 1

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

Neutrons

Protons

Missing electrons

Extra electrons

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

Wide

Infinity

Narrow

Zero

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

Crystal lattice

All of these

Unit cell

Ore

103. The forward resistance of the diode is

Few ohms

Ohms

Many ohms

None of these

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

p-type

Insulator

n-type

Superconductor

105. The least doped region in a transistor is

Base

Either emitter or collector

Emitter

Collector

106. A substance which have empty conduction band is called

Conductor

Insulator

Semiconductor

None of these

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

None of these

Emitter

Collector

Base

108. 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

Each of them decreases

Copper increases and germanium decreases

109. Photovoltaic cell produces electrical energy from

Heat energy

Chemical energy

None of these

Light energy

110. Application of photodiode is/are

None of these

Automatic switching

Detection of visible and invisible radiations

Logic gates

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

Amplifier

Oscillator

Logic gates

Filter

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

Equal to one

Less than one

Greater than one

Of zero

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

Any of above

Base

Collector

Emitter

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

Computers

Electric motors

Electric generations

Transformers

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

Strain

Stress

None of these

Force

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

p-type

n-type

Extrinsic

Intrinsic

117. In half wave rectification

Current flows in one directions

None of these

Current flows in pulses

Only half cycle is used

118. Light emitting diode work when it is

None of these

Reverse biased

Forward biases

Both

119. Which logic gate is represented by following diagram?

AND

EOR

NOR

120. Reverse bias applied on a junction diode

Increase the minority carrier current

Increases the majority carrier current

Raises the potential barrier

Lowers the potential barrier

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

Filtering circuit

An amplifier

Converter

A rectifier

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

None of these

Rectifier

Oscillator

Detector

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

OR gates only

AND gates, OR gates, and NOT gates

Or gates and NOT gates

AND gates and NOT gates

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

N-type material

Semiconductor

P-type material

Super conductor

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

Kilo ohms

Ohms

Several mega ohms

Mega ohms

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

Thousands

Man hundred

None of these

Hundreds

127. The critical temperature for mercury is

1.18 K

7.2 K

3.72 K

4.2 K

128. Which one is reverse-biased?

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

Extra electrons

Neutrons

Protons

Missing electrons

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

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

Its conductivity increases with rise of temperature

It has high resistance to the current flow when reverse biased

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

n-type semiconductor

p-type semiconductor

p-type conductor

n-type conductor

132. Young’s modulus for copper is

None of these

110 Nm¯²

91 x 10 Nm¯²

70 x 10 Nm¯²

133. 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

134. The ratio β represents

135. In Germanium crystal, impurity donor elements have valiancy

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

First A and B

Decreases

Increases

Remains constant

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

Superconductors

Semiconductors

Insulators

Conductors

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

Gallium

Boron

All of above

Aluminum

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

NOR gate

OR gate

NOT gate

AND gate

140. 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

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

mix

any of above

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

None of these

Low

Zero

High

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

N-type semiconductor

P-type semiconductor

N-type conductor

None of these

144. Symbol represents

NOR gate

XNOR gate

NOT gate

NAND gate

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

Raises the potential barrier

Increase the minority carrier current

Lowers the potential barrier

Increase the majority carrier current

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

Slightly less than emitter current

Greater than emitter current

Equal to emitter current

Any of above

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

Almost zero

Infinity

None of these

Zero

148. 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

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

120° Phase shift

No Phase shift

90° Phase shift

180° Phase shift

150. At absolute zero, Si acts as

Metal

None of these

Non-metal

Insulator

151. 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

Base

Emitter

Collector

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

Depends upon the nature of material

Diffusion of charges

Both drift and diffusion of charges

Drift of charges

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

Stress

Strain

None of these

Force

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

Nanosecond

None of these

Microsecond

Millisecond

155. Diode can work as

Oscillator

Rectifier

Modulator

Multivibrator

156. 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.

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

Increase its life

Increase its electrical resistivity

Increases its electrical conductivity

Enable it to Telerate higher voltage

158. 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

Collector

Emitter

159. The thickness of the base is equal to

Mean of thickness of emitter and collector

Very small as compared to the thickness of emitter and collector

Thickness of collector

Thickness of emitter

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

NOT gate

AND gate

OR gate

XOR gate

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

162. 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

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

Variable amplitude

Unit amplitude

Constant amplitude

Zero amplitude

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

Diode

Amplifier

Transistor

Rectifier

165. In a semiconductor, the mobility of holes is

None

Less than electrons

Equal to electrons

Greater than electrons

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

Hidden energy states

Forbidden energy states

None of these

Band levels

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

Electrons

None of these

Holes

Neutrons

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

9.8

4.9

169. Which one is forward bias?

170. 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

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

Arsenic

Aluminum

Antimony

Phosphorus

172. The energy band gap is maximum in

Superconductors

Metals

Insulators

Semiconductors

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

Using a Coolidge tube

Suppressing the harmonics in A.C voltage

Suppressing half wave of A.C supply by using diode

Using a transistor

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

None of these

Common emitter configuration

Common collector configuration

Common base configuration

175. Transistor can be used as

Filter

Half wave rectifier

Amplifier

Full wave rectifier

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

Semiconductor

Superconductor

Insulator

None of these

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

Gamma Rays

x-rays

Electromagnetic Waves

Transverse Waves

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Malik TahirLast Updated: May 26, 2025

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