When the current in a coil changes from 2 A to 4 A in 0.05 s, an electromotive force (e.m.f.) of 8 V is induced in the coil. The coefficient of self-inductance of the coil is:

A step-down transformer connected to an AC mains supply of 220 V operates an 11 V, 44 W lamp. Ignoring power losses, what is the current in the primary circuit?

A transformer has 200 turns in its primary winding and 1000 turns in its secondary winding. What type of transformer is this?