MCQs of Magnetic forces, materials and inductance (Electromagnetics Field - 3140912)

Electromagnetics Field (3140912) MCQs

MCQs of Magnetic forces, materials and inductance

Showing 71 to 80 out of 171 Questions

71.

Which of the following materials has net magnetic moment zero?

(a)	Diamagnetic
(b)	Ferrimagnetic
(c)	Antiferromagnetic
(d)	Antiferrimagnetic

72.

Attraction capacity of electromagnet will increase if the

(a)	Core length increases
(b)	Core area increases
(c)	Flux density decreases
(d)	Flux density increases

73.

Pick up the correct statement

(a)	Conductivity of ferrites is better than ferromagnetic materials
(b)	Conductivity of ferromagnetic materials is better than ferrites
(c)	Conductivity of ferrites is very high
(d)	Conductivity of ferrites is same as that of ferromagnetic materials

74.

Temporary magnets are used in

(a)	Loud-speakers
(b)	Generators
(c)	Motors
(d)	All of above

75.

Main reason of noisy solenoid is

(a)	Strong tendency of fan out of lamination at the end caused by repulsion among magnetic lines of force
(b)	Uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
(c)	Both (a) and (b)
(d)	None of above

76.

Strength of an electromagnet is increased by

(a)	Increasing the cross-sectional area
(b)	Increasing the number of turns
(c)	Increasing current
(d)	All of above

77.

Core of an electromagnet should have

(a)	Low coercivity
(b)	High susceptibility
(c)	Both (a) and (b)
(d)	None of above

78.

Magnetism of a magnet can be destroyed by

(a)	Heating
(b)	Hammering
(c)	Inductive action of another magnet
(d)	All of above

79.

A charge of 10 nC is moving with a velocity of 10⁷(−0.5ā_x+ā_y−0.71ā_z) m/s. What will be the force exerted on the charge due to magnetic induction B = (ā_x+2ā_y+3ā_z) mWb/m² and electric field E = (3ā_x+2ā_y+ā_z) kV/m?

(a)	(0.47ā_x+0.1ā_y−0.91ā_z) mN
(b)	(4.7ā_x+ā_y−9.1ā_z) mN
(c)	(0.47ā_x+0.1ā_y−0.91ā_z) N
(d)	(4.7ā_x+ā_y−9.1ā_z) kN

80.

A charge of −1.2 C is moving with a velocity of v = (5ā_x+2ā_y−3ā_z) m/s. What will be the force exerted on the charge due to magnetic induction B = (−4ā_x+4ā_y+3ā_z) Wb/m² and electric field E = (−18ā_x+5ā_y−10ā_z) V/m?

(a)	(0ā_x−2.4ā_y−21.6ā_z) kN
(b)	(0ā_x−2.4ā_y−21.6ā_z) N
(c)	(0ā_x−24ā_y−216ā_z) N
(d)	(0ā_x+2.4ā_y+21.6ā_z) N

Showing 71 to 80 out of 171 Questions