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

Here all the spokes are identical and connected in parallel and so same induced emf is obtained across all the spokes. Hence, we should find induced emf across any one spoke. Let it be `epsilon`. . Here,
`epsilon=1/2 B omegaR^2 " " omega=(120xx2pi)/60=4pi"rad"/"sec"`
`=1/2(0.4xx10^(-4))(4pi)(0.5)^2`
`=0.2xx10^(-4)xx4xx3.14xx0.25`
`therefore epsilon=6.28xx10^(-5)` V