Eddy Currents

Eddy Currents are currents set up in a conductor in response to a changing magnetic field. They flow in closed loops in a plane perpendicular to the magnetic field..

In the first exhibit, when a strong magnet is dropped down the copper, aluminium and perxpex tubes, it is seen that the magnet slows down considerably while falling through aluminium or copper tubes. This phenomenon is known as Lenz's Law. The magnetic field induced in the metal due to Eddy Current attracts the falling magnet, creating resistance. This resistance is what slowed down your magnet.

We can see that the magnet falls faster through the aluminium tube. Aluminium has a greater resistance than Copper, so the eddy currents from the falling magnet are weaker in the aluminum than in the copper at the same velocity.

In the second exhibit, a large magnet is made to fall towards a large block of copper. It can be seen that the magnet stops abruptly in front of the copper block and does not touch it. This is also due to the repelling magnetic field due to the induced eddy current in the copper.

Click to see poster

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