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

Question : 21

Function of rectifier is

a) To convert D.C. into A.C.

b) To convert A.C. into D.C.

c) Both (a) and (b)

d) None of these

Question : 22

The permanent magnet is made from which one of the following substances?

a) Ferromagnetic

b) Diamagnetic

c) Paramagnetic

d) Electromagnetic

Question : 23

Which impurity is doped in Si to form n-type semiconductors?

a) B

b) As

c) Al

d) None of these

Question : 24

For dynamo which one of the following statements is correct?

a) It converts the kinetic energy into heat energy

b) It converts the mechanical energy into electrical energy

c) It converts the electrical energy into light energy

d) It converts the electrical energy into mechanical energy

Question : 25 [IAS (Pre) 1998]

Assertion (A):
The temperature of a metal wire rises when an electric current is passed through it.
Reason (R):
Collision of metal atoms with each other releases heat energy.
Code

a) (A) is true, but (R) is false

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

c) Both (A) and (R) are true, but (R) is not the correct explanation of (A)

d) (A) is false, but (R) is true