Question

A conducting disc of radius r rotates with a small but constant angular velocity w about its axis. A uniform magnetic field B exists parallel to the axis of rotation. Find the motional emf between the centre and the periphery of the disc.

Answer 1

Velocity at a distance $\frac{r}{2}$ from the centre

$=\frac{r\omega }{2}$

$E=Blv=B\times R\times \frac{r\omega }{2}$

$=\frac{1}{2}B{r}^2\omega .$