Electromagnetic InductionNEET Physics · Class 12 · NCERT Chapter 6

You can expect 1 to 2 questions in NEET 2027. The chapter has high PYQ frequency. Faraday's law applications, motional EMF, Lenz's law direction, self-inductance and energy stored in an inductor are favourites.

Whenever the magnetic flux through a closed loop changes, an EMF is induced in the loop equal to minus the rate of change of flux. epsilon equals minus d Phi over dt. For N turns, multiply by N. The induced EMF drives a current if the loop is closed.

The direction of the induced current is such that it OPPOSES the change in flux that produced it. This is the meaning of the negative sign in Faraday's law. Lenz's law follows from energy conservation: if the induced current aided the change, you could create energy out of nothing.

A conducting rod of length L moving with velocity v perpendicular to a magnetic field B (with v perpendicular to L) develops EMF epsilon equals B L v across its ends. This is induced EMF without any time-varying field; the change of flux comes from the rod sweeping out new area.

Currents induced in bulk pieces of conductor by a changing flux. They form swirling loops, hence the name. Eddy currents heat up the conductor, dissipating energy. They are useful in induction stoves and magnetic braking, and undesirable in transformer cores (laminations reduce them).

When the current through a coil changes, the changing flux through itself induces a back EMF. epsilon equals minus L di over dt. L is the self-inductance, in henries (H). For a long solenoid, L equals mu_0 N squared A over length.

Building up current I from zero in an inductor requires work, which is stored in the magnetic field. U equals half L I squared. Energy density (in vacuum) is u equals B squared over (2 mu_0).