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

Question : 26 [IAS (Pre) 1996]

Some pairs of devices and associated energy changes are given below.

1. Electric generator - Mechanical to electrical
2. Electric motor - Electrical to mechanical
3. Diesel engine - Light to electrical
4. Solar cell - Chemical to mechanical

a) 2 and 4

b) 1 and 2

c) 1 and 3

d) 3 and 4

Question : 27 [NDA]

When an optician prescribes a – 5D lens, what does it mean?

a) Concave lens of 5 cm focal length

b) Concave lens of 20 cm focal length

c) Convex lens of 5 cm focal length

d) Convex lens of 5 cm focal length

Question : 28 [PCS (Pre) 2008]

The device used for converting alternating current to direct current is called

a) Transformer

b) Inverter

c) Rectifier

d) Transmitter

Question : 29

The part of the transistor which is heavily doped to produce large number of majority carriers is

a) base

b) collector

c) emitter

d) any of the above depending upon the nature of transistor

Question : 30

Which of the following is the most suitable material for making permanent magnet ?

a) Copper

b) Steel

c) Soft iron

d) Nickel