^Electromagnetic induction

^Electromagnetic induction

Faraday discovered that a time-varying magnetic field produces an electric field more precisely time varying magnetic flux linked with a circuit induces an electric field in it. This field is non conservative & forms closed loops in the circuit in which it is induced (unlike electrostatic electric field, which never forms closed loop & is conservative). Line integral of this electric field gives emf induced (ε) it lasts as long as the change in magnetic flux continues & is defined as (Called Faraday flux rule)

This electric field pushes the charges around the circuit, if the circuit is closed & has say resistance R, a current starts flowing in it, given by .

The emf induced is independent of resistance of the circuit but current depends on resistance.

Work done in moving a charge around in induced electric field in a cyclic path is not zero, & W = q ε.

The charge induced doesn’t depend on the rate of change of the magnetic flux, instead is depends on the net change in flux & is .