set 2 MCQ Questions & Answers Detailed Explanation

Question : 1

When an n–p–n transistor is used as an amplifier then

a) holes flow from emitter to collector

b) electrons flow from collector to emitter

c) electrons flow from emitter to collector

d) electrons flow from battery to emitter

Question : 2

A coin in a beaker filled with water appears raised. This phenomenon occurs because of the property of

a) total internal reflection of light

b) reflection of light

c) refraction of light

d) interference of light

Question : 3

Electrically charged particles from space travelling at speeds of several hundred km/sec can severely harm living beings if they reach the surface of the Earth. What prevents them from reaching the surface of the Earth?

a) Moisture in the upper layers of atmosphere prevents them from reaching the surface of the Earth

b) The Earth’s magnetic field diverts them towards its poles

c) Ozone layer around the Earth reflects them back to outer space

d) None of the statements (a), (b) and (c) given above is correct

Question : 4

The energy band gap is maximum in

a) superconductors

b) insulators

c) metals

d) semiconductors

Question : 5

Regarding a semiconductor which one of the following is wrong?

a) There are no free electrons at 0K

b) The number of free electrons increases with rise of temperature

c) There are no free electrons at room temperature

d) The charge carriers are electrons and holes

Question : 6

Which gas is filled in normal tubelights?

a) Mercury vapour with argon

b) Sodium vapour with argon

c) Sodium vapour with neon

d) Mercury vapour with neon