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

At least one input is LOW

All inputs are LOW

At least one input is HIGH

All inputs are HIGH

2. 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

Output

Virtual input

3. 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

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

Capacitor is used

Solvent is used

Resistor is used

None of these

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

None of these

Require more current

Works efficiently

Damaged

6. In a P-type semiconductor

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

Major current carriers are mobile holes

Major current carriers are mobile negative ions

Major current carriers are electrons

7. 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

Diode is forward biased

Diode is reverse biased

None of these

8. The ratio β represents

9. Reverse bias applied on a junction diode

Increase the minority carrier current

Raises the potential barrier

Increases the majority carrier current

Lowers the potential barrier

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

Depletion region

Charged region

Diffusion region

None of these

11. The number of junctions in the PNP transistor are

12. The energy band gap is maximum in

Semiconductors

Metals

Insulators

Superconductors

13. Which one is reverse-biased?

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

Suddenly increases

Remain fixed

Decreases slowly

Increases slowly

15. 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

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

Missing electrons

Neutrons

Protons

Extra electrons

17. NAND gate is

A universal gate

Not a universal gate

A basic gate

A basic universal gate

18. Radio waves of constant amplitude can be generated with

Rectifier

Filter

FET

Oscillator

19. Light emitting diode work when it is

Both

None of these

Reverse biased

Forward biases

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

1 cm

10¯¹² cm

1 mm

10¯⁶ cm

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

Antimony

Indium

Phosphorus

Arsenic

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

Semiconductor

Superconductor

None of these

Insulator

23. Depletion layer consists of

Electrons

Protons

Immobile ions

Mobile ions

24. LDR means:

Low degree resistor

Light dependent resistance

Low degree radiations

None of these

25. At absolute zero, Si acts as

Insulator

Non-metal

None of these

Metal

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

mix

any of above

27. 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

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

None of these

N-type semiconductor

P-type semiconductor

N-type conductor

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

Solar cells

The light emitting diode

The photo diodes

The switch

30. Arsenic, antimony or phosphorus are impurities of

may be p-type or n-type

None of these

n-type

p-type

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

Protons

Holes

Neutrons

Electrons

32. Diode can work as

Multivibrator

Oscillator

Modulator

Rectifier

33. The working of transistor as amplifier is similar to

Step up transformer

Triode vacuum tube

Three diodes in common

Step down transformer

34. 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

35. In Germanium crystal, impurity donor elements have valiancy

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

Dual carriers

Minority carriers

Blockers

Majority carriers

37. Semi-conductor germanium and silicon are

Pentavalent

Trivalent

Divalent

Tetravalent

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

Its conductivity increases with rise of temperature

It has high resistance to the current flow when reverse biased

It has low resistance to the current flow when forward biased

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

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

Increases

Remains constant

First A and B

Decreases

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

None of these

Detector

Oscillator

Rectifier

41. In semiconductors at a room temperature

The conduction band is completely empty

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

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

The valence band is completely filled

42. 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

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

Amplification

Rectification

All of these

Magnification

44. A piece 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

45. Young’s modulus for copper is

None of these

91 x 10 Nm¯²

70 x 10 Nm¯²

110 Nm¯²

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

Emitter

Base

Collector

Any of above

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

Filter

Logic gates

Amplifier

Oscillator

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

Using a Coolidge tube

Suppressing half wave of A.C supply by using diode

Using a transistor

Suppressing the harmonics in A.C voltage

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

Extra electrons

Neutrons

Missing electrons

Protons

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

Bulk’s modulus

Young’s modulus

Modulus of electricity

None of these

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

Increase the majority carrier current

Lowers the potential barrier

Raises the potential barrier

Increase the minority carrier current

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

Very low

Very high

Almost negligible

Zero

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

Free electrons

None of these

Valence electrons

Tightly bound electrons

54. In forward bias the width of potential barrier

Remains same

No effect

Decreases

Increases

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

None of these

Zero

Low

High

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

0.67 V

0.5 V

0.9 V

0.7 V

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

Boron

All of above

Aluminum

Gallium

58. The least doped region in a transistor is

Collector

Emitter

Base

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

Large number of free electrons and few holes

Large number of holes and electrons

Equal number of free electrons and holes

Large number of holes and few electrons

60. 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

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

AND gates

NAND gates

OR gates

NOT gates

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

Boron

Phosphorus

Aluminum

Gold

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

Remains unchanged

Decreases

Increases

Decreases and then increases

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

Resistance of copper increases while that of germanium decreases

Resistance of copper decreases while that of germanium increases

Resistance of both increases

Resistance of both decreases

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

9.8

4.9

66. 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):

NOR

AND

NAND

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

Stress

Strain

Force

None of these

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

Aluminum

Phosphorus

Arsenic

Antimony

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

Increases

Decreases

Decreases and then increases

Remains unchanged

70. The ratio β shows the

Input resistance

Voltage gain

None of these

Current gain

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

Intrinsic

Extrinsic

n-type

p-type

72. Zener breakdown in a semiconductor diode occurs when

Forward current exceeds certain value

Reverse bias exceeds certain value

Potential barrier is reduced to zero

Forward bias exceeds certain value

73. The least doped region in a transistor is

Base

Collector

Emitter

Either emitter or collector

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

Forward bias

Doping density

Diode design

Temperature

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

n-type conductor

p-type conductor

p-type semiconductor

n-type semiconductor

76. Which logic gate is represented by following diagram?

EOR

NOR

AND

77. The operation of a transistor requires

That the collector be heated

That the base be heated

None of these

That the emitter be heated

78. 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

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

To A.C.

None of these

In reverse bias

In forward bias

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

Semiconductor

Conductor

Insulator

Alloy

81. The critical temperature for mercury is

1.18 K

7.2 K

4.2 K

3.72 K

82. 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

83. A NAND gate has:

LOW inputs and a HIGH output

LOW inputs and a LOW output

None of these

HIGH inputs and a HIGH output

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

Protons

Missing of electrons

Neutrons

Extra electrons

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

OR gate

NAND gate

AND gate

NOT gate

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

OR gate

Comparator

AND gate

INVERTER gate

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

All of these

Crystal lattice

Unit cell

Ore

88. Identify the correct statement about minority carriers

Holes in n-type and p-type

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

Free electrons in n-type and p-type

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

89. Acceptor and donor impurities donate

n-carriers and p-carriers respectively

n-carriers only

p-carriers only

p-carriers and n-carriers respectively

90. 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

AND gate

NOR gate

OR gate

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

Superconductors

Semiconductors

Insulators

Conductors

92. In a PN junction

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

Undetermined

93. A diode as a rectifier converts:

A.C. into D.C.

High voltage to low voltage

Low voltage to high voltage

D.C. into A.C.

94. A transistor consists of

Three PN-junctions

Two PN-junctions

Four PN-junctions

One PN-junction

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

Base

Emitter

Any of the above depending on nature of transistor

Collector

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

Electric motors

Computers

Transformers

Electric generations

97. In semiconductors at a room temperature

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

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

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

4.9

9.8

99. n-type semiconductor if formed

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

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

From pure Ge crystal

From pure Si crystal

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

Potential barrier in depletion layer remains unchanged

Diode is forward based

Potential barrier in depletion layer increases

Diode is reverse biased

101. In insulators

Conduction 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

Valence band is partially filled with electrons

102. An OP-AMPs can amplify

D.C.

A.C.

Both A.C. & D.C.

None of these

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

All of these

Aluminum

Gallium

Boron

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

Enable it to Telerate higher voltage

Increase its electrical resistivity

Increase its life

Increases its electrical conductivity

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

p-type

n-type

Intrinsic

Extrinsic

106. In the transistor schematic symbol, the arrow

Point from north to south

Is located on the base

Is locate on the collector

Is located on the emitter

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

Emitter

Collector

Base

Can be any of the above three

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

AND gates, OR gates, and NOT gates

OR gates only

Or gates and NOT gates

AND gates and NOT gates

109. A n-p-n transistor conducts when

Both collector and emitter are positive 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

Both collector and emitter are negative with respect to the base

110. Which one is forward bias?

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

Transverse Waves

Electromagnetic Waves

Gamma Rays

x-rays

112. The energy band gap is maximum in

Insulators

Metals

Semiconductors

Superconductors

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

Zero amplitude

Variable amplitude

Unit amplitude

Constant amplitude

114. Reverse bias applied on a junction diode

Increase the minority carrier current

Lowers the potential barrier

Increases the majority carrier current

Raises the potential barrier

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

Narrow

Infinity

Wide

Zero

116. N-type crystal is

Positively charged

None of these

Negative charged

Neutral

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

None of these

Nanosecond

Millisecond

Microsecond

118. Which is normal used of transistor?

Diode

P-type material

Rectifier

Switching device

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

Strain

None of these

Stress

Force

120. The forward resistance of the diode is

Few ohms

Ohms

Many ohms

None of these

121. 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 high inputs resistance to the input current

It offers a very low open loop gain all of above

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

n-type conductor

p-type conductor

n-type semiconductor

p-type semiconductor

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

Rectifier

Amplifier

Transistor

Diode

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

Bulk modulus

None of these

Young’s modulus

Shear modulus

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

Man hundred

None of these

Thousands

Hundreds

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

Equal number of free electrons and holes

Large number of holes and electrons

Large number of holes and few electrons

Large number of free electrons and few holes

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

Increase its electrical resistivity

Increase its electrical conductivity

Increase its life

Enable it to Telerate higher voltage

128. A diode as a rectifier converts:

Low voltage to high voltage

A.C. into D.C.

D.C. into A.C.

High voltage to low voltage

129. Non-inverting amplifier circuits have

A very low input impedance

A very high input impedance

None of these

A low output impedance

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

Band levels

Forbidden energy states

None of these

Hidden energy states

131. Photodiode is used for

Light display

Emission of light

Detection of light

None of these

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

Electrons and holes

Electrons and protons

Holes and electrons

Protons and electrons

133. 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

134. 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

135. In Germanium crystal, impurity donor elements have valiancy

136. Depletion region of a junction is formed

Under reverse bias

During the manufacturing process

Under forward bias

When temperature varies

137. In a semiconductor, the mobility of holes is

Equal to electrons

None

Less than electrons

Greater than electrons

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

Base

None of these

Emitter

Collector

139. The thickness of the base is equal to

Thickness of emitter

Thickness of collector

Mean of thickness of emitter and collector

Very small as compared to the thickness of emitter and collector

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

A rectifier

Converter

Filtering circuit

An amplifier

141. To use a transistor as an amplifier

Both junctions are forward biased

Both junctions are reverse biased

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

No bias voltages are required

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

Antimony

Phosphorus

Arsenic

Aluminum

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

Logic gates

Oscillator

Filter

Amplifier

144. 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

145. At absolute zero, Si acts as

None of these

Metal

Non-metal

Insulator

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

NOT gate

AND gate

XOR gate

OR gate

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

Electric field is zero

Electric field is maximum

Potential is zero

Potential is maximum

148. Transistor can be used as

Full wave rectifier

Amplifier

Filter

Half wave rectifier

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

Common collector configuration

Common base configuration

Common emitter configuration

None of these

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

Less than one

Equal to one

Greater than one

Of zero

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

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

P-type material

Amplifier

Oscillator

Rectifier

153. In insulators

Valence band is partially filled with electrons

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

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

No Phase shift

180° Phase shift

90° Phase shift

120° Phase shift

155. Photovoltaic cell produces electrical energy from

None of these

Heat energy

Chemical energy

Light energy

156. A substance which have empty conduction band is called

Insulator

Conductor

Semiconductor

None of these

157. Symbol represents

NOR gate

NAND gate

NOT gate

XNOR gate

158. A pieced 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

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

Electrons

Holes

None of these

Neutrons

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

Electric field is maximum

Potential is maximum

Potential is zero

Electric field is zero

161. 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

Depends upon the nature of material

Both drift and diffusion of charges

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

Inverting terminal is at high potential

Both are at the high potential

Both are at the same potential

Non-inverting terminal is at high potential

163. In half wave rectification

Only half cycle is used

Current flows in one directions

Current flows in pulses

None of these

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

On switch

Capacitor

Inductor

Off switch

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

n-type

Insulator

Superconductor

p-type

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

N-type material

Super conductor

P-type material

Semiconductor

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

Holes move from emitter to base

Holes move from base to emitter

Electrons move from base to collector

Holes move from emitter be base

168. In a n-p-n transistor:

Holes move from emitter to base

Negative charge moves from emitter to base

Negative charge moves from collector to base

Holes move from base to collector

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

Tensile stress

None of these

Shear stress

Compress ional stress

170. Application of photodiode is/are

None of these

Automatic switching

Detection of visible and invisible radiations

Logic gates

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

n-type conductor

p-type conductor

n-type semiconductor

p-type semiconductor

172. The positive sign of gain indicates that

Input and out signals are in phase

May be in phase or not

Input and out signals are not in phase

None of these

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

Infinity

Zero

None of these

Almost zero

174. With negative feedback, the returning signal:

Aids the input signal

Opposes the input signal

Is proportional to output current

Is proportional to differential voltage gain

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

Greater than emitter current

Any of above

Slightly less than emitter current

Equal to emitter current

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

Increased by forward biasing

Increased by reverse biasing

Decreased by reverse biasing

Is independent of voltage

177. Polythene, potystrene and nylon are examples of

Amorphous solids

Polymeric solids

Crystalline solids

Glassy solids

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Malik TahirLast Updated: May 26, 2025

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