Practice Lenz's Law in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

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

Nature resists change — when you push a magnet into a coil, the coil creates its own magnetic field that pushes back.

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)?

Example 2

medium
A circular loop is in a magnetic field pointing into the page. The field strength decreases. According to Lenz's law, in which direction does the induced current flow?

Example 3

medium
A conducting ring is dropped through a region of magnetic field. As it enters the field, the induced current creates an upward force on the ring. Explain this using Lenz's law.

Example 4

hard
A superconducting ring (zero resistance) is in a magnetic field of 0.5 \text{ T}. The external field is suddenly turned off. What happens to the flux through the ring, and why?
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