Electromagnetism: Mutual & Self-Induction

Mutual Induction This occurs when two coils are in close proximity to one another A changing magnetic field in one coil induces an emf in the other coil

Transformer A device used to change the voltage of A.C. power supplies It consists of a secondary coil wrapped around a primary coil, which is wrapped around a transformer core Vi/Vo =  Np/ Ns Vi = input voltage Vo = output voltage Np = number of turns in the primary coil Ns = number of turns in the secondary coil

Uses of transformers Mobile phone chargers Televisions Computers Power stations

Self-Induction When a changing magnetic field in a coil induces an emf in the coil itself  This emf opposes the voltage across the coil (according to Lenz's law) and hence is called a back emf

Uses of Inductors Dimmer switches Radios

Inductor A device used to induce a back emf Used to reduce the current flowing in a A.C. circuit Consists of a coil of wire with a number of turns, this is wrapped around a soft iron core

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