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Figure 1: Because of eddy current damping, the aluminum bar will need a few seconds to pass through
the high magnetic field.
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This demo shows almost ideal damping. The aluminum bar shown in figure 1 is not attracted by the strong magnets, because aluminum is not magnetic. However, aluminum does conduct electrical currents and therefore is subjected to eddy current damping when passing through a magnetic field. Eddy currents are electrical currents induced by a changing magnetic field. When held still in the magnetic field, the aluminum bar is not subjected to any force caused by the magnetic field. When the bar has a certain velocity, the eddy current damping will make a velocity dependent force counteracting the direction of the velocity.
Using very strong magnets makes the phenomenon very clear. Please be advised to be carefull and take the necessary precausions when dealing with these magnets. The force pulling together a strong magnet and any magnetic material, will increase quadratically with the distance in between and will easily crush a finger!
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Figure 2: Demo of closed coil vs. open coil damping
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The demo shown in figure 2 shows there is a big difference in damping between an open coil circuit and a closed one. If the coil is closed, the mechanical energy is transformed by the coil into an electric current. Because of resistance losses, this circuit produces a well feelable damping.
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