A bicycle wheel is mounted vertically on a metal axle in a horizontal magnetic field, as shown in the diagram. Sliding connections are made to the metal edge of the wheel and to the metal axle.

(b) The wheel rotates five times per second and has a radius of $15 \mathrm{cm}.$ The magnetic flux density may be assumed to be uniform and of value $5.0\times {10}^{-3}$ $T.$

(i) the area swept out each second by one spoke