Electromagnetism MCQs

Question 1

The relative permeability of a feromagnetic material is

Accepted Answer

more than 100 or 1000

Answer

less than one

Answer

more than one

Answer

more than 10

Question 2

The unit of magnetic flux is

Accepted Answer

weber

Answer

henry

Answer

amper re/metre

Answer

ampe e-turn/weber

Question 3

Relative permeability of vacuum is

Accepted Answer

1

Answer

I H/m

Answer

1/4n

Answer

4n x 10-7 H/m

Question 4

The magnetising force (H) and magnetic flux density are connected by the relation

Accepted Answer

B = IAN

Answer

B = prH/i.to

Answer

B = H/p.opl.

Answer

B = goH/pr

Question 5

Energy stored by a coil is doubled when its currest is increased by ...... percent.

Accepted Answer

41.4

Answer

25

Answer

50

Answer

100

Question 6

The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is .... A/s

Accepted Answer

20

Answer

50

Answer

0.05

Answer

500

Question 7

A material for should have

Accepted Answer

high retentivity

Answer

low hysteresis loss

Answer

high permeability

Answer

low retentivity

Question 8

In a magnetic material hysteresis loss takes place primarily due to

Accepted Answer

it high retentivity

Answer

rapid reversals of its magnetization

Answer

flux density lagging behind magnetising force

Answer

molecular friction

Question 9

Silicon steel is used in electrical machines because it has

Accepted Answer

low hysteresis loss

Answer

low co-ercivity

Answer

low retentivity

Answer

high co-ercivity