Lenz's Law, Right Hand Rule, Induced Current, Electromagnetic Induction - Physics

Lenz's Law states that an induced electromotive force (EMF) always produces a current whose magnetic field opposes the original change in magnetic flux that created it. The induced EMF is proportional to the rate of change of magnetic flux, and the negative sign in the formula signifies opposition.

Consider a coil moving into a constant magnetic field pointing out of the page. As the coil enters, the magnetic flux through it increases. To oppose this increase, the induced current creates an induced magnetic field pointing into the page. Using the right-hand rule, this implies a clockwise current in the coil.

The right-hand rule states that if you point your thumb in the direction of the current in a wire, your curled fingers indicate the direction of the magnetic field generated by that current. For a current going up, the magnetic field is into the page on the right and out of the page on the left. The reverse is true for a current going down.

Imagine a coil moving away from a magnetic field pointing into the page. As it moves away, the magnetic flux through the coil decreases. To oppose this decrease and try to maintain equilibrium, the system generates an induced magnetic field in the same direction as the external field (into the page). This results in a clockwise induced current.

Consider a long wire with a current flowing to the right, and a circular coil above it. The magnetic field created by the wire above it points out of the page. If the current in the long wire decreases, the magnetic flux through the coil also decreases. To oppose this decrease, the induced magnetic field will be in the same direction, out of the page. Applying the right-hand rule, this leads to a counter-clockwise induced current in the coil.

Lenz's Law fundamentally describes the system's attempt to maintain a state of equilibrium. If magnetic flux increases, the induced current creates a magnetic field to decrease it. If flux decreases, the induced current creates a magnetic field to increase it, thus opposing or supporting the change to restore balance.