1
MCQ (Single Correct Answer)

AIPMT 2010 Prelims

Which one of the following statement is false ?
A
Pure Si doped with trivalent impurities gives a p-type semiconductor.
B
Majority carries in a n-type semiconductor are holes.
C
Minority carries in a p-type semiconductor are electrons.
D
The resistance of intrinisic semiconductor decreases with increase of temperature.

Explanation

In a n-type semiconductors, electrons are majority carriers and holes are minority carriers.
2
MCQ (Single Correct Answer)

AIPMT 2010 Prelims

To get an output Y = 1 in given circuit which of the following input will be correct ?

A
A $$ \to $$ 1,  B $$ \to $$ 0,  C $$ \to $$ 0
B
A $$ \to $$ 1,  B $$ \to $$ 0,  C $$ \to $$ 1
C
A $$ \to $$ 1,  B $$ \to $$ 1,  C $$ \to $$ 0
D
A $$ \to $$ 0,  B $$ \to $$ 1,  C $$ \to $$ 0

Explanation



The Boolen expression for the given combination is

output Y = (A + B) ยท C

So it is clear that Y = 1, when A = 1, B = 0 and C = 1
3
MCQ (Single Correct Answer)

AIPMT 2009

Sodium has body centred packing. Distance between two nearest atoms is 3.7 $$\mathop A\limits^ \circ $$. The lattice parameter is
A
4.3 $$\mathop A\limits^ \circ $$
B
3.0 $$\mathop A\limits^ \circ $$
C
8.6 $$\mathop A\limits^ \circ $$
D
6.8 $$\mathop A\limits^ \circ $$

Explanation

Distance between nearest atoms in body centred cubic lattice (bcc),

d = $${{\sqrt 3 } \over 2}a$$

Given d = 3.7 $$\mathop A\limits^ \circ $$

$$ \therefore $$ $$a = {{3.7 \times 2} \over {\sqrt 3 }}$$ = 4.3 $$\mathop A\limits^ \circ $$
4
MCQ (Single Correct Answer)

AIPMT 2009

A transistor is operated in common-emitter configuration at VC = 2V such that a change in the base current from 100 $$\mu $$A to 200 $$\mu $$A produces a change in the collector current from 5 mA to 10 mA. The current gain is
A
100
B
150
C
50
D
75

Explanation

Current gain, $$\beta $$ = $${{\Delta {I_C}} \over {\Delta {I_B}}}$$

= $${{\left( {10 - 5} \right) \times {{10}^{ - 3}}} \over {\left( {200 - 100} \right) \times {{10}^{ - 6}}}}$$ = 50

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