electric current and magnetism - Category wise Question and Answer Practice Test with Solutions

Question : 26

Gases are good conductors of electricity at

a) low pressure

b) low temperature

c) high pressure

d) high temperature

Question : 27 [NDA]

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 : 28 [UPPCS (Mains) 2011]

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 : 29 [NDA]

The polarity of an unmarked horse shoe magnet can be determined by using

a) an electroscope

b) a charged glass rod

c) a magnetic compass

d) another unmarked bar magnet

Question : 30

In an n-type silicon, which of the following statement is true?

a) Electrons are minority carriers and pentavalent atoms are the dopants.

b) Holes are minority carriers and pentavalent atoms are the dopants.

c) Electrons are majority carriers and trivalent atoms are the dopants.

d) Holes are majority carriers and trivalent atoms are the dopants.