Lenz's Law Video Lessons

Concept

# Problem: A bar magnet is dropped through a vertical copper tube and is observed to fall very slowly, despite the fact that mechanical friction between the magnet and the tube is negligible.  Which of following best explains the reason for this? A. The falling magnet magnetizes the copper pipe which causes the now permanent copper pipe magnet to attract the falling magnet thus causing the slower descent. B. The falling magnet is slowed by the Earth’s magnetic field. C. The changing flux of the falling magnet induces a magnetic field in the copper pipe, in the opposite direction of the bar magnet's field, which impedes the movement through the pipe. D. Friction and Air resistance cause the magnet to fall much slower than it would outside of the tube.

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###### Problem Details

A bar magnet is dropped through a vertical copper tube and is observed to fall very slowly, despite the fact that mechanical friction between the magnet and the tube is negligible.  Which of following best explains the reason for this?

A. The falling magnet magnetizes the copper pipe which causes the now permanent copper pipe magnet to attract the falling magnet thus causing the slower descent.

B. The falling magnet is slowed by the Earth’s magnetic field.

C. The changing flux of the falling magnet induces a magnetic field in the copper pipe, in the opposite direction of the bar magnet's field, which impedes the movement through the pipe.

D. Friction and Air resistance cause the magnet to fall much slower than it would outside of the tube.