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 `1G =10^(-4)T.`

Explanation

From the result derived in example 2, emf induced in each metallic spoke is given by
`epsilon=(BomegaL^(2))/(2)` Here, `B=H_(E)=0.4G=0.4 xx 10^(-4)T`
`omega=120 "rev" // "min"`
`=(120 xx 2pi)/(60) "rad" // s=4pi "rad" // s`
L=length of each spoke=0.5 m
`epsilon=(0.4 xx 10^(-4) xx 4pi xx (0.5)^(2))/(2)`
`=0.68 xx 10^(-5) V`
All the 10 metallic spoke are connected in parallel, emf across them is the same.