^Mutual induction (M)
1. Property of a coil due to which it suppress the variations in current in it by inducing a back EMF in the neighbouring coil is called mutual induction. It is measured by a quantity called mutual inductance (M), which is defined as, .
2. SI unit of both self & mutual inductance is henry (H).
3. For two long coaxial solenoid wound on same core,
4. Reciprocity theorem: M12 = M21