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#### Question

(a) Explain the meaning of the term mutual inductance. Consider two concentric circular coils, one of radius r_{1} and the other of radius r_{2} (r_{1} < r_{2}) placed coaxially with centres coinciding with each other. Obtain the expression for the mutual inductance of the arrangement.

(b) A rectangular coil of area A, having number of turns N is rotated at 'f' 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.

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