Science Friday: Not Sorcery … An Anti-Gravity-Like Experiment You Can Perform Today | The Fibonacci Sequence in “Lateralus”, by tool | Arthur Benjamin on The magic of Fibonacci numbers

Just to be clear, it’s not anti-gravitational, it just seems that way. And it’s not magic, it just seems that way. The reality is that it’s the physics of the world in which we live.

Why does the magnet fall so slowly? It’s a combination of Faraday’s and Lenz’s Laws. The falling magnet isn’t attracted to copper (non ferrous metal), but the movement through, or over, or near the copper or aluminum (watch the video below) which induces a current that causes a change in the magnetic flux that reacts with the magnetic field of the the magnet itself. More

Diagram

The magnet induces currents in the copper pipe as it falls because, at any point in the pipe, there is a change in magnetic flux. By Faraday’s Law this induces and emf, and hence a current that, by Lenz’s Law, opposes the motion. So as the magnet falls vertically, the change in flux below the falling magnet produces a repulsive force, i.e., an upward force (opposite to gravity), and the change in flux above the falling magnet produces an attractive force, i.e., an upward force also (opposite to gravity). The magnitude of these upward forces depends on the speed of the magnet, the faster the magnet falls the greater the upward force. When the upward force equals the weight of the magnet, the latter will reach its terminal velocity (since there will be no net force acting on it). With a plastic pipe, an emf is generated, but since plastic is an insulator, there will be no currents and so there will be no upward forces.


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