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

Question : 16 [NDA]

If the electrical resistance of a typical substance suddenly drops to zero then the substance is called

a) conductor

b) superconductor

c) semiconductor

d) insulator

Question : 17 [NDA]

Consider the following statement: The principle of total internal reflection is applicable to explain the

1. Formation of mirage in desert.
2. Formation of image in microscope.
3. Colour of evening sky.
4. Operation of optical fibres.

a) 2 and 3

b) 1 and 4

c) 3 and 4

d) 1 and 2

Question : 18 [UPPCS (Mains) 2007]

A device which converts electrical energy into mechanical energy is

a) Electric motor

b) Dynamo

c) Transformer

d) Inductor

Question : 19

Earth’s magnetic field always has a horizontal component except at

a) geographical north pole

b) magnetic equator

c) magnetic pole

d) at an altitude of 45°

Question : 20

To shield an instrument from external magnetic field, it is placed inside a cabin made from

a) iron

b) wood

c) ebonite

d) diamagnetic substance