Basic Concept of Electricity MCQs

Question 1

Two inductive coils with self inductance L1 and L2 are magnetically coupled in series opposing and in parallel aiding respectively. The mutual inductances between the coils in the two cases are respectively.L1 L2 ? M2

Accepted Answer

(b) + L2 ? 2M, Li + L2 + 2m

Answer

Li + L2 + 2M,

Answer

Li + L2 ? 2M

Answer

(c) Li + L2 ? 2M, I + L2 ? 2M

Question 2

Two coupled coils with L1 = L2 = 0,611 have a coupling coefficient of k = 0.8.NI The turn ratio ? is N2

Accepted Answer

1

Answer

4

Answer

12

Answer

0.5

Question 3

Magnetic staturation of iron means

Accepted Answer

none of the above.

Answer

the state when changes in magnetics field strength H causes a little change in the magnetic flux density B.

Answer

the state when a little change in magnetic field strength H causes a larger change in the magnetic flux density.

Answer

magnetization of iron to the maximum extent.

Question 4

The coercive force in a ferrowmagnetic material is related to the

Accepted Answer

intercept on the negative 1-1 axis of the B-H loop

Answer

area enclosed by the B-H loop.

Answer

intercept on the positive B axis of the B-H loop

Answer

maximum value of B on the B-H loop

Question 5

Hysteresis loss is caused by

Accepted Answer

structural non-homogeneity

Answer

work required for magnetizing the material

Answer

potential work function

Answer

none of the above

Question 6

Hysteresis loss is proportional to

Accepted Answer

f

Answer

f15

Answer

f2

Answer

f3k

Question 7

The energy stored in the magnetic field of a solenoid 30 cm. long and 3 cm diameter would with 1,000 turns of wire carrying current of 10 A is

Accepted Answer

0.15

Answer

0.015 J

Answer

1.153

Question 8

A coil with a certain number of turns has a specified time constant. If the number of turns is doubled, its time constance would

Accepted Answer

become double

Answer

remain unaffected.

Answer

become four fold.

Answer

get halved

Question 9

At a certain current, the energy stored a an iron-corred coil is 1,000 J and its copper loss is 2,000W. The time constant (in seconds) of the coil is

Accepted Answer

1

Answer

0.25

Answer

0.5

Answer

2