Total Energy calculation of permanent magnet

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Discussion Overview

The discussion centers around the calculation of the total energy of a permanent magnet, specifically focusing on the energy available from the magnet to perform work. Participants explore various aspects of magnetic energy, including its extraction and the implications of magnetic field interactions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants inquire about the context of the question, asking whether it pertains to a school project or personal interest, and seek clarification on what is meant by "total energy" of the magnet.
  • One participant suggests that calculating the energy contained in the magnetic fields created by the magnet may be a way to approach the question, but notes that this may not equate to the total energy available for work.
  • Another participant raises the idea that extracting energy from a magnet's magnetic field interactions could lead to a decrease in field strength, complicating the extraction process.
  • Concerns are expressed regarding the conservative nature of magnetic fields, where energy expended to move objects towards the magnet is returned when those objects are moved back, posing challenges for energy extraction.
  • One participant acknowledges the relationship between the magnetic field and the varying air gap between the poles, seeking further information on this aspect.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to calculate the total energy of a permanent magnet or the feasibility of extracting energy from it. Multiple competing views and uncertainties remain regarding the nature of magnetic energy and its practical implications.

Contextual Notes

The discussion highlights limitations in understanding the assumptions behind energy extraction from magnetic fields, the dependence on definitions of energy in this context, and unresolved questions about the mechanics involved in energy transfer.

Shantaram
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Does anyone know how to calculate the total energy of magnet?
Thanks!
 
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Shantaram said:
Does anyone know how to calculate the total energy of magnet?
Thanks!

Welcome to the PF. What is the context of your question? Is it a school question, a school project, or for personal interest? What do you know about magnets and energy so far? Do you mean the energy required to initially magnetize a permanent magnet, or the energy available from a permanent magnet to do work on something? What kind of something?
 
Thanks for reply.
Its my personal interest to know about the permanent magnet.
I meant,total energy avilable from the magnet to do some work.
 
Probably the best way to do it is to calculate the energy contained in the magnetic fields created by the magnet. But that is probably not the same as the total energy available. It is an interesting question to ponder about whether or not we could actually extract all the energy from a magnet through its magnetic field interactions. This is because the force exerted is proportional to the field strength. As we extract energy from the magnetic fields, their strength must decrease to reflect the appropriate reduction in the energy density of the fields. Thus, the amount of mass that can be moved decreases since we have to overcome such environmental forces as gravity or friction.

EDIT: Not only that but a magnet field is conservative. If I use a magnet to draw close a pin, it exerts force and expends energy. However, if I take the pin and move back to its original position, I give back the same energy to the magnetic field. So now we have a problem, let's say we have millions of these pins and we want to extract all the energy by having the magnet pull in these pins. But we cannot clear away the pins after they are pulled in since this returns energy to the magnet. So now the pins have to pile up on th magnet, this means that the next pin can only be pulled in over a smaller and smaller distance. And the farther we go away from the magnet, the weaker the field is. So the energy in the fields is locked in locally to the magnet. It is another problem to get at this energy without being forced to use objects to heavy to pull in and too low in density to pull in a large number to a close proximity.
 
Thanks!
Yes, you are right.The magnetic field is change with respect to varying airgap between poles.
can I get any brief information on this?
 

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