Electronics and Communication Practice Test

12th Standard Physics — Electronics and Communication: Online Practice Test

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The barrier potential of a silicon diode is approximately,

A.0.7 V B.0.3V C.2.0 V D.2.2V

If a small amount of antimony (Sb) is added to germanium crystal,

A.it becomes a p-type semiconductor B.the antimony becomes an acceptor atom C.there will be more free electrons than hole in the semiconductor D.its resistance is increased

In an unbiased p-n junction, the majority charge carriers (that is, holes) in the p-region diffuse into n-region because of

A.the potential difference across the p-n junction B.the higher hole concentration in p-region than that in n-region C.the attraction of free electrons of n-region D.All of the above

If a positive half-wave rectified voltage is fed to a load resistor, for which part of a cycle there will be current flow through the load?

A.\(0^{\circ}–90^{\circ}\) B.\(90^{\circ}–180^{\circ}\) C.\(0^{\circ}–180^{\circ}\) D.\(0^{\circ}–360^{\circ}\)

The zener diode is primarily used as

A.Rectifier B.Amplifier C.Oscillator D.Voltage regulator

The principle based on which a solar cell operates is

A.Diffusion B.Recombination C.Photovoltaic action D.Carrier flow

The light emitted in an LED is due to

A.Recombination of charge carriers B.Reflection of light due to lens action C.Amplification of light falling at the junction D.Large current capacity.

The barrier potential of a p-n junction depends on i) type of semiconductor material ii) amount of doping iii) temperature. Which one of the following is correct?

A.(i) and (ii) only B.(ii) only C.(ii) and (iii) only D.(i) (ii) and (iii)

To obtain sustained oscillation in an oscillator,

A.Feedback should be positive B.Feedback factor must be unity C.Phase shift must be 0 or \(2\pi\) D.All the above

Q10

If the input to the NOT gate is A = 1011, its output is

A.0100 B.1000 C.1100 D.0011

Q11

The given electrical network is equivalent to

A logic gate network consisting of interconnected NAND or NOR gates.

A.AND gate B.OR gate C.NOR gate D.NOT gate

Q12

The output of the following circuit is 1 when the input ABC is

A combination of logic gates with three inputs labeled A, B, and C.

A.101 B.100 C.110 D.010

Q13

The variation of frequency of carrier wave with respect to the amplitude of the modulating signal is called

A.Amplitude modulation B.Frequency modulation C.Phase modulation D.Pulse width modulation

Q14

The frequency range of 3 MHz to 30 MHz is used for

A.Ground wave propagation B.Space wave propagation C.Sky wave propagation D.Satellite communication

Q15

At room temperature, what are the forbidden energy gap values for Silicon and Germanium respectively?

A.0.7 eV and 1.1 eV B.1.1 eV and 0.7 eV C.6 eV and 1 eV D.1 eV and 6 eV

Q16

Why are semiconductors described as having a negative temperature coefficient of resistance?

A.Resistance increases with temperature B.Resistance decreases as temperature rises C.Resistance remains constant regardless of temperature D.Conductivity decreases as temperature rises

Q17

In an intrinsic semiconductor at room temperature, what is the relationship between the number of electrons in the conduction band and holes in the valence band?

A.More electrons than holes B.More holes than electrons C.Equal number of electrons and holes D.No holes are present

Q18

Which group of elements is used as dopants to create an n-type extrinsic semiconductor from pure silicon?

A.Group III trivalent elements B.Group V pentavalent elements C.Group IV tetravalent elements D.Noble gases

Q19

What is the primary cause for the formation of a depletion region near a p-n junction?

A.Application of forward bias B.Diffusion of majority charge carriers C.Application of reverse bias D.Doping with neutral atoms

Q20

By what factor does the reverse saturation current of a silicon diode increase for every 10 degree Celsius rise in temperature?

A.It stays the same B.It is halved C.It doubles D.It triples

Q21

What is the theoretical maximum efficiency of a full wave rectifier circuit?

A.40.6 percent B.50 percent C.81.2 percent D.100 percent

Q22

In which region of its V-I characteristics is a Zener diode primarily operated for voltage regulation?

A.Forward bias region B.Breakdown region C.Saturation region D.Cut-off region

Q23

What physical property of the semiconductor material determines the specific color of light emitted by a Light Emitting Diode (LED)?

A.The size of the diode B.The amount of forward current C.The energy band gap of the material D.The type of casing used

Q24

According to Kirchhoff's law applied to a bipolar junction transistor, how are the emitter (IE), base (IB), and collector (IC) currents related?

A.IB = IE + IC B.IC = IE + IB C.IE = IB + IC D.IE = IB - IC

Q25

When a transistor is used as an amplifier in a common emitter configuration, what is the phase relationship between the input signal and the output signal?

A.They are in phase B.Output lags by 90 degrees C.Output is reversed by 180 degrees D.Output leads by 270 degrees

Q26

Which Barkhausen condition must be satisfied for a transistor circuit to maintain sustained oscillations?

A.Negative feedback must be used B.The loop gain must be unity C.The phase shift must be 90 degrees D.The loop gain must be zero

Q27

In digital electronics, which logic gate produces a high output (1) only when all of its inputs are high?

A.OR gate B.AND gate C.NAND gate D.XOR gate

Q28

According to De Morgan's first theorem, a NOR gate is logically equivalent to which other arrangement?

A.Bubbled OR gate B.Bubbled AND gate C.NAND gate followed by NOT D.XOR gate

Q29

Which mode of electromagnetic wave propagation is typically used for radio frequencies between 3 MHz and 30 MHz by reflecting signals off the ionosphere?

A.Ground wave propagation B.Sky wave propagation C.Space wave propagation D.Satellite communication

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About this Electronics and Communication test

This free online practice test covers Electronics and Communication from the 12th Standard Physics (Samacheer Kalvi) syllabus. Choose the number of questions and an optional time limit, then answer and submit — everything is checked in your browser, with the correct answers and a worked explanation shown at the end. For the full solutions to every question in this set, see the solved MCQs page.

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