 JEE Mains Previous Years Questions with Solutions

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1

AIEEE 2004

For a transistor amplifier in common emitter configuration for load impedance of $1k\,\Omega$ $\left( {{h_{fe}} = 50} \right.$ and $\left. {{h_{oe}} = 25} \right)$ the current gain is
A
$-24.8$
B
$-15.7$
C
$-5.2$
D
$-48.78$

Explanation

In common emitter configuration current gain

${A_i} = {{ - h{f_e}} \over {1 + {b_{0c}}{R_L}}}$

$= {{ - 50} \over {1 + 25 \times {{10}^{ - 6}} \times 1 \times {{10}^3}}}$

$= - 48.78$
2

AIEEE 2004

The manifestation of band structure in solids is due to
A
Bohr's correspondence principle
B
Pauli's exclusion principle
C
Heisenberg's uncertainty principle
D
Boltzmann's law

Explanation

Pauli's exclusion principle.
3

AIEEE 2004

A piece of copper and another of germanium are cooled from room temperature to $77K,$ the resistance of
A
copper increases and germanium decreases
B
each of them decreases
C
each of them increases
D
copper decreases and germanium increases

Explanation

Copper is a conductor, so its resistance decreases on decreasing temperature as thermal agitation decreases; whereas germanium is semiconductor therefore on decreasing temperature resistance increases.
4

AIEEE 2004

When $npn$ transistor is used as an amplifer
A
electrons move from collector to base
B
holes move from emitter to base
C
electrons move from base to collector
D
holes move from base to emitter

Explanation

Electrons move from base to emmitter.