. In a uniform magnetic field of induction B a wire in the form of a semicircle of radius r rotates about the diameter of the circle with an angular fre

In a uniform magnetic field of induction B a wire in the form of a semicircle of radius r rotates about the diameter of the circle with an angular frequency ï·. The axis of rotation is perpendicular to the field. If the total resistance of the circuit is R the mean power generated per period of rotation is