Question

A copper disc of radius 0.1 m is rotated about its centre with 20 revolution per second in a uniform magnetic field of 0.1 T with its plane perpendicular to the field. The emf induced across the radius of the disc is –

• A. $\frac{\pi}{20}$volt
• B. $\frac{\pi}{10}$ volt
• C. 20 p millivolt
• D. 100 p millivolt

Answer 1

Answer: (C)

20 p millivolt

Answer 2

e = $\frac{B\omega R^{2}}{2}$

= $\frac{0.1 \times (2\pi \times 20)(0.1)^{2}}{2}$

= 20 p × 10^–3 volt