Massachusetts Institute of Technology
Sign in

MIT Physics Demo -- Pendulum and Magnet

A solid copper pendulum is mounted between the poles of an electromagnet (solenoid). The pendulum is set into motion, and then the magnets are turned on. The magnets induce eddy currents in the copper which oppose the motion of the pendulum. The pendulum quickly slows to a stop, demonstrating an effect called eddy current braking. Eddy current brakes are widely used in trains and roller coasters.

When a copper pendulum with strips cut into it is swung between the same magnets, it is not slowed nearly as much as the solid pendulum. This is because the cuts in the copper prevent large eddy currents from forming. Only eddy currents smaller than the strips of copper can be formed.

Comments (1)

why does the perforated copper plate slow down less than the solid pendulum?

Posted almost 8 years by Anonymous User

You need to log in, in order to post comments.

April 15, 2008 11:50
Creative Commons Attribution-NonCommercial (What is this?)
Additional Files

46649 times

More from MIT Department of Physics Technical Services Group

MIT Physics Demo -- Centrifugal versus Centripetal Motion

MIT Physics Demo -- Centrifugal ver...

Added 8 years ago | 00:01:18 | 37257 views

MIT Physics Demo -- Telegraph Transmitter

MIT Physics Demo -- Telegraph Trans...

Added over 8 years ago | 00:00:36 | 54182 views

Ripple Tank: Single and Double Slit Diffraction and Interference

Ripple Tank: Single and Double Slit...

Added over 7 years ago | 00:03:05 | 62368 views

The Coriolis Effect

The Coriolis Effect

Added 7 years ago | 00:03:00 | 89868 views

Soap Film Oscillation

Soap Film Oscillation

Added over 7 years ago | 00:04:27 | 49630 views

MIT Physics Demo -- Microwave Polarization

MIT Physics Demo -- Microwave Polar...

Added over 8 years ago | 00:01:14 | 37589 views