If a copper disc is rotated rapidly below a freely suspended magnetic needle, the magnetic needle shall start rotating with a velocity
A. less than that of disc but in opposite direction
B. equal to that of disc and in the same direction
C. equal to that of disc and in the opposite direction
D. less than that of disc and in the same direction
Answer: Option D
Which of the following is a vector quantity?
A. Relative permeability
B. Magnetic field intensity
C. Flux density
D. Magnetic potential
What is the magneto-motive force (mmf) of a wire with 8 turns carrying three amperes of current?
A. 2,400 At
B. 240 At
C. 24 At
D. 2.4 At
Magnetism of a magnet can be destroyed by
A. heating
B. hammering
C. by inductive action of another magnet
D. by all above methods
Strength of an electromagnet can be increased by
A. increasing the cross-sectional area
B. increasing the number of turns
C. increasing current supply
D. all above methods
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