Calculate the self-inductance of a toroidal coil consisting of 1000 turns of wire, each of radius 1 cm wound uniformly on a non-ferromagnetic ring of mean radius 10 cm. (1 (b A circuit containing an air-cored solenoid of self-inductance 0.1 H carries a steady current of 1 A. A switch in the circuit is opened, reducing the current to zero in a time of 1 ms. Determine the magnitude of the induced emf across the solenoid, assuming the current falls to zero at a constant rate. [1]