In 1834, Russian physicist Heinrich Lenz discovered the directional relationships between induced magnetic fields, voltage, and current when a conductor is passed within the lines of force of a magnetic field. Lenz's law states:

"An induced electromotive force generates a current that induces a counter magnetic field that opposes the magnetic field generating the current."

This interactive Java tutorial explores how the movement of a bar magnet influences induced current in a stationary conductor. Operating instructions appear below the tutorial window.

To operate the tutorial, use your mouse to click and drag the magnet toward and away from the conducting ring.

When the field lines of the magnet (illustrated above in red) approach the conductor ring, a resulting electromagnetic force and current is generated within the ring. The current (illustrated within the conductor ring as yellow electrons) induces a magnetic field (blue lines of force) in the ring. Notice that the direction of the induced magnetic field within the ring is oriented in a direction opposite to that of the approaching magnetic field generated by the bar magnet.