A wheel with 10 metallic spokes each 0.5 m long is rotated with a speed of 120 rev/min in a plane normal to the horizontal component of earth’s magnetic field `H_E` at a place. If `H_E` = 0.4 G at the place, what is the induced emf between the axle and the rim of the wheel? Note that `1 G = 10^(-4)` T.

Explanation

Induced emf = `(1//2) omega B R^2`
`= (1//2) xx 4pi xx 0.4 xx 10^(-4) xx (0.5)^2`
`=6.28 xx 10^(-5) V`
The number of spokes is immaterial because the emf’s across the spokes are in parallel.