Question

A uniform circular metal disc of radius $R$ is rotating about a vertical axis passing through its center and perpendicular to its plane with constant frequency f. If $B_H$ and $B_v$ are horizontal and verticaI components of the Earth's magnetic field respectively, then the induced e.m.f between its center and the rim is

• A. $\pi\,B_vfR^2$
• B. $\pi \,B_HfR^2$
• C. $\pi B_vfR^2$
• D. Zero

Answer 1

Answer: (C)

$\pi B_vfR^2$

Answer 2

$e = \frac{1}{2} BR^2 \omega$ where $\omega = 2 \pi f$