Q. A circular coil of mean radius of $7\ cm$ and having 400 turns is rotated at the rate of 1800 revolutions per minute in the earth’s magnetic field ($B = 0.5$ gauss), the maximum e.m.f. induced in coil will be
A) $1.158\ V$
B) $0.58\ V$
C) $0.29\ V$
D) $5.8\ V$
Explanation
(b) $e_{0} = \omega NBA = (2\pi v)NB\left( \pi r^{2} \right) = 2 \times \pi^{2}v\ NBr^{2}$
$= 2 \times (3.14)^{2} \times \frac{1800}{60} \times 4000 \times 0.5 \times 10^{- 4} \times \left( 7 \times 10^{- 2} \right)^{2}$
$= 0.58\ V$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.