SELF INDUCTANCE
When an electric circuit with a coil is switched on, the increase of current through the coil with time causes a back e.m.f. to be induced in the coil, from Lenz`s law , this opposes the current flow. We call this effect self indcutance. We measure self inductance L in Henrys, symbol H. A coil with self inductance of 1 Henry produces a back E.M.F. of 1 volt for every 1 A s^-1 current change.

EDDY CURRENTS
When a metal object is moved in an electric field, the free electrons in it are excited into moving, these are refered to as eddy currents, these oppose the motion. Eddy currents are used in electromagnetic braking systems. Iron cores, in transformers or inductors are usually laminated, that is divided into layers to stop large eddy currents flowing and causing the core to become to hot.