Question

A circular coil of mean radius of 7 cm and having 4000 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

Answer 1

Answer: (B)

0.58 V

Answer 2

$e_{0} = \omega NBA = (2\pi\nu)NB(\pi r^{2}) = 2 \times \pi^{2}\nu\mspace{6mu} NBr^{2}$

$= 2 \times (3.14)^{2} \times \frac{1800}{60} \times 4000 \times 0.5 \times 10^{- 4} \times (7 \times 10^{- 2})^{2}$

$= 0.58\mspace{6mu} V$