set 4 MCQ Questions & Answers Detailed Explanation

Question : 1

Gases are good conductors of electricity at

a) low pressure

b) low temperature

c) high pressure

d) high temperature

Question : 2

Refractive index of an optical medium changes with

1. the nature of the medium.
2. the change in the angle of incidence of the ray.
3. colour of the incident ray.

a) 1 and 2 only

b) 1 and 3 only

c) 2 and 3 only

d) 1, 2 and 3

Question : 3

Transformer is used for

a) To step up DC voltages

b) Converting AC into DC

c) Converting DC into AC

d) To step up or step down AC voltages

Question : 4

Assertion (A) :
A myopic person is advised to use concave lens.
Reason (R) :
The eye lens of a myopic person focuses the parallel rays coming from distant objects in front of the retina.

a) A is true but R is false

b) Both A and R are individually true and R is the correct explanation of A

c) Both A and R are individually true but R is NOT the correct explanation of A

d) A is false but R is true

Question : 5

Which one of the following is correct? Lightning is formed, when

a) strong opposite charges in different clouds break down the resistance offered by intervening air

b) similar charges of electricity rush towards each other and then get repelled

c) clouds strike against impurities in air and hte friction burns up these impurities

d) water vapour produces electricity in the clouds

Question : 6

The Earth’s magnetic field is due to

a) Moving charges in space outside

b) Currents circulating inside the core

c) Presence of a huge magnet at its centre

d) None of the above