1. Property of a coil due to which it suppress the variations in current in it by inducing a back EMF in itself is called self induction. It is measured by a quantity called self inductance (L), which is
2. For a coil & long solenoid
(a) self inductance, L = A l μm n2
(b) Magnetic energy is,
(c) Magnetic energy density is,
3. An inductor (also called a solenoid, or long coil or electromagnet) bent in the form of a coil & made from a thick wire of negligible resisitivity so as to have zero ohmic resistance e. R = 0 is called an ideal inductor or solenoid.