Demonstration Manual

Electricity and Magnetism

DEM44-1 - Eddy Currents Induced by a Linearly-Moving Magnet

Objective:

- To show the effects of a moving magnetic field opposing Eddy Currents induced in a hollow copper pipe.

Apparatus:

• Copper pipe
• Copper, aluminum and iron cylinders
• Neodymium magnet

Method:

• The copper tube is clamped vertically


• The copper, aluminum and iron cylinders are dropped through the tube, with no effect.


• The Neodymium magnet is then dropped through the tube.

Observe that:

• The magnet slows down, arriving at the end after a noticeably longer time than with the cylinders.

The moving magnet has induced circulating currents whose own magnetic field opposes that of the magnet.

   Watch an Eddy Currents Induced by a Linearly-Moving Magnet video demonstration on Youtube

Note: in the video an aluminum pipe (which is also non-magnetic) is used instead of a copper pipe.

- Video Created at Utah State University by Professor Boyd F. Edwards and assistants.