A wheel with 8 matallic spokes each 50 cm long is rotated with a speed of 120 `rev//min` in a plane normal to horizontal component of earth's magnetic field. Earth's magnetic field at the phase is 0.4 G and angle of dip `60^(@)`. Calculate the emf induced between the axle and rim of the wheel. How is the emf affected if number of spokes is increased ?

Explanation

`because H = B cos delta = 0.4 cos 60^(@) = 0.2 G = 0.2 xx 10^(-4) T`
This component is parallel to the plane of the wheel. Thus, the emg induced is given as,
`E = (1)/(2) BI^(2) omega`,
Where,
`omega = (2 pi N)/(l)`,
`E=(1)/(2) xx 0.2 xx 10^(-4) xx (0.5)^(2)xx(2 xx 3.14 xx 120)/(60)=3.14 xx 10^(-5)V`.
The value of emg induced is independent of the number of spokes as the emf's across the spokes are in parallel. So, the emf will be unaffected with the increase in spokes.