A cycle wheel of radius 0.5 ~m is rotated with constant angular...

When a conducting disc or wheel of radius $r$ rotates with constant angular velocity of $\omega$ about its axis in a uniform magnetic field perpendicular to its plane and parallel to its axis of rotation, then,
Induced emf is given by, $\mathrm{e}=\frac{1}{2}{\mathrm{~B} \omega \mathrm{r}^2}^2$ Here, $B=0.1 \mathrm{~T}, \omega=10 \mathrm{rad} / \mathrm{s}, \mathrm{r}=0.5 \mathrm{~m}$ Substituting these values in Eq. (i), we get \therefore \quad $\mathrm{e}=\frac{1}{2} \times$0.1 $\times$10 $\times($0.5)^2=$\frac{1}{8} \mathrm{~V}=$0.125 $\mathrm{~V}$