Here’s something your kids will love: Some very
strange things happen when you drop a magnet down a copper tube — almost
as if some mysterious invisible force grabs hold of the object, slowly
guiding it through.
It’s not mysterious at all, however. It’s just science.
Electric currents and magnetic fields are closely
related. If you have one, you often have (or can create) the other. The
braking effect that happens to the magnet at it travels down the tube is
due to an eddy current. That’s an electrical current that forms in the copper in response to the magnetic field that generated by the moving magnet.
The eddy current then creates a magnetic field of
its own, causing the two magnetic fields to overlap, thus slowing the
magnet as it falls.
Watch:
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