A circular coil of radius 10 cm,500 turns and resistance 2 ohm is placed with its plane perpendicular to the component of earth's magnetic field.It is rotated about its vertical diameter through 180 degrees in 0.25s.Estimate the magnitudes of emf and current induced in the coil.Horizontal component of earth's magnetic field at the place is 3 x 10^-5 Tesla.

net flux through the coil: N x area of coil x field crossing perpendicular to the coil

thus

initial flux = 15.7 x 3 x 10^-5 = 47.1 x 10^-5 Wb

final flux = 0      (because no part of flux is now perpendiclar to it)

thus change in flux = =47.1 x 10^-6 Wb

emf induced = -(rate of change of flux) = 1.88 x 10^-3 V

and current = emf/resistance of coil  = 0.94 x 10^-3 A