30. Induction and Inductance

A 30mH inductor carries a current of 500mA. If the circuit is opened and the current stops over a period of 3.0μs, what potential develops across the inductor?

A toroidal solenoid has mean radius 12.0 cm and crosssectional area 0.600 cm². How many turns does the solenoid have if its inductance is 0.100 mH?

The inductor shown in Fig. E30.11 has inductance 0.260 H and carries a current in the direction shown. The current is changing at a constant rate. The potential between points a and b is V_ab = 1.04 V, with point a at higher potential. Is the current increasing or decreasing?