Semiconductor

NEET Physics · 93 questions · Page 9 of 10 · Click an option or "Show Solution" to reveal answer

Q81

If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be

A 25 Hz

B 50 Hz

C 70.7 Hz

D 100 Hz

Correct Answer

Option D

Solution

In full wave rectifier the fundamental frequency in ripple is twice of input frequency.

Q82

A n-p-n transistor conducts when

A both collector and emitter are positive with respect to the base

B collector is positive and emitter is negative with respect to the base

C collector is positive and emitter is at same potential as the base

D both collector and emitter are negative with respect to the base

Correct Answer

Option B

Solution

When the collector is positive and emitter is negative with respect to base, it causes the forward biasing for each junction, which causes conduction of current.

Q83

Barrier potential of a p-n junction diode does not depened on

A diode design

B temperature

C forward bias

D doping density

Correct Answer

Option A

Solution

Barrier potential does not depend in diode design while barrier potential depends upon temperature, doping density and forward biasing.

Q84

Reverse bias applied to a junction diode

A lowers the potential barrier

B raises the potential barrier

C increases the majority carrier current

D increases the minority carrier current

Correct Answer

Option B

Solution

In reverse bias, the size of the depletion region increases thereby increasing the potential barrier.

Q85

The given truth table is for which logic gate

\begin{array}{lll}A & B & Y \\ 1 & 1 & 0 \\ 0 & 1 & 1 \\ 1 & 0 & 1 \\ 0 & 0 & 1 \end{array}

A NAND

B XOR

C NOR

D OR.

Correct Answer

Option A

Solution

This truth table represents NAND gate.

Q86

In a p-n junction

A high potential at n side and low potential at p side

B high potential at P side and low potential at n side

C p and n both are at same potential

D undetermined.

Correct Answer

Option B

Solution

For conduction, p-n junction must be forward biased.

For this p-side should be connected to higher potential and n-side to lower potential.

Q87

Number of atom per unit cell in B.C.C.

A 9

B 4

C 2

D 1

Correct Answer

Option C

Solution

In body-centred cubic (b.c.c.) lattice there are eight atoms at the corners of the cube and one at the centre.

Therefore number of atom per unit cell =

{1 \over 8} \times 8

+ 1 = 2

Q88

For a transistor

{{{I_C}} \over {{I_E}}}

= 0.96, then current gain for common emitter is

A 12

B 6

C 48

D 24

Correct Answer

Option D

Solution

{{{I_C}} \over {{I_E}}}

= 0.96 = $\alpha$ $\therefore$ Current gain, $\beta$ =

{{{I_C}} \over {{I_B}}}

{\alpha \over {1 - \alpha }}

= 24

Q89

The given truth table is for which logic gate

\begin{array}{lll}A & B & Y \\ 1 & 1 & 0 \\ 0 & 1 & 1 \\ 1 & 0 & 1 \\ 0 & 0 & 1 \end{array}

A NAND

B XOR

C NOR

D OR

Correct Answer

Option A

Solution

This truth table represents NAND gate.

Q90

For a common base circuit if

{{{I_C}} \over {{I_E}}}

= 0.98 then current gain for common emitter circuit will be

A 49

B 98

C 4.9

D 25.5.

Correct Answer

Option A

Solution

{{{I_C}} \over {{I_E}}}

= 0.98 = $\alpha$ $\therefore$ Current gain, $\beta$ =

{{{I_C}} \over {{I_B}}}

{\alpha \over {1 - \alpha }}

= 49

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