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#Copper Pipes Experiment

Experiments with magnets and conductors

Copper Pipes

Description:

This is an excellent demonstration of Lenz's law and eddy currents. When a magnet is dropped through a vertical copper pipe, it falls much slower than a steel ball would. Its rate of fall quickly reaches a terminal velocity and it takes much longer for it to fall out of the other end than a steel ball would take.

Construction:

There is nothing that has to be built or put together for this demonstration. All that is needed is a strong magnet (for example, a NIB measuring 1/2 diameter, about 1/8 thick) and three or four copper pipes of different sizes. The following table details the copper pipes I used:

(the air gap is the space between the magnet and the inside wall of the pipe)

(all of the pipes except for the special thick wall pipe can be obtained from most hardware stores)

(the 5th pipe in the picture is actually a red brass thick walled pipe, not as good a conductor as the copper one, number 4)

(the two thick-walled pipes were obtained from Central Wire and Steel. Cost is $250 for a 12' piece!)