A wheel with 10 metallic spokes, each 0.50 m long, is rotated with a speed of 120 rev/minute in a plane normal to the earth's magnetic field at the place. If the magnitude of the field is 0.40 gauss, what is the induced emf between the axle and the rim of the wheel?

Explanation

f= 120 rev/min= 2 rev/second,
B= 0.40 gauss `= 0.4 xx 10^(-4)T`, Area swepty, by each spoker per second, `A= pi r^(2)f`
Magnetic flux cut by each spoke per second, `(d phi_(B))/(dt)= BA = B pi r^(2)f`
Induced emf, `e= B pi r^(2)f` (numerically)
`e= 0.4 xx 10^(-4) xx (22)/(7) xx 0.5 xx 0.5 xx 2`
`e= 6.29 xx 10^(-5)` volt