Lenz's Law

Lenz's law: the direction of induced current is such that it OPPOSES the change producing it.

If flux INTO the loop is increasing, induced current circulates so that its field points OUT of the loop (to oppose the increase).

If flux is decreasing, induced current creates a field in the SAME direction as the (decreasing) original field — trying to maintain it.

This is a direct consequence of CONSERVATION OF ENERGY — if induced current AIDED the change, energy would appear from nothing.

When you push a magnet toward a coil, the induced current makes the coil-face FACING the magnet a repelling pole (same pole). You feel resistance — that mechanical work becomes electrical energy.

Pulling the magnet away makes the facing coil-face attracting (opposite pole) — again the force opposes your motion.

Lenz's law sets the SIGN of the EMF in Faraday's law: ε = −N·dΦ/dt.