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

Question : 21

Eddy currents are produced when

a) a metal is kept in steady magnetic field

b) a circular coil is placed in a magnetic field

c) a metal is kept in varying magnetic field

d) through a circular coil, current is passed

Question : 22 [UPPCS (Pre) 1992]

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

Question : 23 [NDA]

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 : 24

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 : 25 [NDA]

What is the essential difference between a terrestrial telescope and an astronomical telescope?

a) A terrestrial telescope forms an erect image while an astronomical telescope forms an inverted image

b) One of the lenses in a terrestrial telescope is concave

c) The final image formed in a terrestrial telescope is virtual

d) A terrestrial telescope forms an inverted image while an a stronomical telescope forms an erect image