Where does the energy come from?

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Discussion Overview

The discussion centers on the source of kinetic energy when iron is attracted to a magnet, exploring concepts of potential energy and energy conservation in a magnetic field. It involves theoretical considerations related to magnetism and energy transformations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that the kinetic energy of the iron comes from its potential energy in the magnetic field, which is converted to kinetic energy when the iron is released.
  • Another participant expresses uncertainty about their previous understanding, indicating a potential correction based on a prior discussion.
  • A later reply asserts that the initial claim about energy considerations in the context of permanent magnets and ferromagnetic materials is indeed correct, challenging the previous uncertainty.

Areas of Agreement / Disagreement

The discussion reflects disagreement regarding the interpretation of energy sources in this context, with some participants supporting the initial claim while others express doubt or confusion.

Contextual Notes

There are unresolved assumptions regarding the definitions of potential and kinetic energy in magnetic contexts, as well as the implications of energy conservation principles.

goodboy
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put a iron beside a magnet,then we konw the iron would be attracted toward the magnet.but where does the kinetic energy of the iron come from?
 
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The iron is in a magnetic field, hence it has potential energy due to its position. This becomes KE when the iron is released. The total energy, KE+PE, is conserved.
 
Tomsk said:
Actually, I just read this thread: https://www.physicsforums.com/showthread.php?t=130549. Looks like I'm wrong then...:rolleyes:
You are now wrong. You were right the first time. For a permanent magnet and ferromagnetic iron, the energy considerations do work just as they would in electrostatics with a charge attractilng a polarizable object.
 

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