Question

A copper disc of radius 0.1 m rotates about its centre with 10 revolutions per second in a uniform magnetic field of 0.1 Tesla. The emf induced across the radius of the disc is

• A. $\frac{\pi }{10}V$
• B. $\frac{2\pi }{10}V$
• C. $10\pi mV$
• D. $20\pi mV$

Answer 1

The correct option is C $10\pi mV$

The induced emf between centre and rim of the rotating disc is
$E=\frac{1}{2}B\omega R^2=\frac{1}{2}\times 0.1\times 2\pi \times 10\times (0.1{)}^2=10\pi \times {10}^{-3}volt$