Practice question · Multiple choice
You drop a strong magnet down a copper pipe (copper is not magnetic). The magnet falls strangely slowly. Why?
Hints
- The moving magnet changes the magnetic flux through every ring of the pipe. What does a changing flux do in a conductor?
- Lenz’s law: induced currents always fight the change that created them. Fighting a falling magnet means pushing it… which way?
Show the answer
B. Falling flux induces eddy currents opposing the motion
Why
Each pipe section experiences changing flux, driving circular eddy currents that create fields opposing the magnet’s motion, braking it. No contact, no friction: this is exactly how magnetic brakes on roller coasters and high-speed trains work.
Practise Electromagnetic Induction and Faraday's Law
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