71.

When npn transistor is used as amplifier

• electrons move from base to collector

• holes move from emitter to base

• electrons move from collector to base

• electrons move from collector to base

For a transistor amplifier in common emitter configuration having load impedance of 1 kΩ (h_fe = 50 and h_oe = 25) the current gain is

• -5.2

• -15.7

• -24.8

• -24.8

A piece of copper and another of germanium are cooled from room temperature to 77 K, the resistance of

• each of them increases

• each of them decreases

• copper decreases and germanium increases

• copper decreases and germanium increases

The manifestation of band structure in solids is due to

• Heisenberg’s uncertainty principle

• Pauli’s exclusion principle

• Bohr’s correspondence principle

• Bohr’s correspondence principle

When p-n junction diode is forward biased

• the depletion region is reduced and barrier height is increased

• the depletion region is widened and barrier height is reduced.

• both the depletion region and barrier height reducedboth the depletion region and barrier height reduced

• both the depletion region and barrier height reducedboth the depletion region and barrier height reduced