When a magnet moves through a copper pipe, it experiences electromagnetic induction due to the changing magnetic field as it enters and exits the pipe. This process generates eddy currents in the copper material, which creates opposing magnetic fields according to Lenz's Law.
Why the Magnet Moves Slower:
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Induction of Eddy Currents: As the magnet approaches the copper pipe, the changing magnetic field induces currents (eddy currents) in the conductive copper. These currents flow in circles perpendicular to the magnetic field and produce their own magnetic fields that oppose the motion of the magnet.
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Lenz's Law: According to Lenz's Law, the induced currents act to oppose the change causing them. Thus, as the magnet falls through the pipe, the induced magnetic field from the eddy currents resists the motion of the magnet, effectively slowing it down compared to when it is outside the pipe.
Why the Magnet Moves Faster:
- Reduced Resistance Outside the Pipe: When the magnet is outside the copper pipe, it does not experience any significant opposing forces from induced eddy currents. Therefore, it falls freely, primarily influenced by gravity, which results in a faster movement.
In summary, the combination of electromagnetic induction and Lenz's Law explains why the magnet travels slower through the copper pipe due to the opposing forces generated by eddy currents, while it moves faster outside the pipe where such forces are absent. This behavior can be vividly observed in demonstrations where a magnet is dropped through a copper tube, illustrating these principles in action.
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