Lenz's Law Physics Example 1

Follow the full solution, then compare it with the other examples linked below.

Example 1

easy
A north pole of a magnet is pushed toward a coil. According to Lenz's law, what pole does the coil's nearest face become? In which direction does the induced current flow (viewed from the magnet's side)?

Solution

  1. 1
    Lenz's law states the induced current opposes the change that caused it.
  2. 2
    The approaching north pole increases the flux through the coil. To oppose this increase, the coil must create a magnetic field that repels the magnet.
  3. 3
    The nearest face of the coil becomes a north pole (repelling the incoming north pole), so the current flows counterclockwise when viewed from the magnet's side.

Answer

Coil face becomes north pole; current flows counterclockwise (from magnet’s view)\text{Coil face becomes north pole; current flows counterclockwise (from magnet's view)}
Lenz's law is a consequence of energy conservation. The induced current always creates effects that oppose the change in flux, requiring work to be done to maintain the change.

About Lenz's Law

The direction of an induced current is always such that it opposes the change in magnetic flux that produced it.

Learn more about Lenz's Law →

More Lenz's Law Examples

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Example 3 medium

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Example 4 hard

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