(i) Explain the meaning of the term mutual inductance. Consider two concentric circular coils, one of radius r1 and the other of radius r2 (r1 < r2) placed co-axially with centers coinciding with each other. Obtain the expression for the mutual inductance of the arrangement.
(ii) A rectangular coil of area A, having number of turns N is rotated at 
revolutions per second in a uniform magnetic field B, the field being perpendicular to the coil. Prove that the maximum emf induced in the coil is 2 πf NBA.
