# Do two magnets separated by a distance have potential energy relative

by jaredvert
Tags: distance, energy, magnets, potential, separated
 P: 62 To each other??? Repondez!
 Homework Sci Advisor HW Helper Thanks P: 12,953 You should be able to figure that out - what is the definition of potential energy?
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Do two magnets separated by a distance have potential energy relative

 Quote by jaredvert Yes but I know of no equation for potential energy between magnets.
See http://hyperphysics.phy-astr.gsu.edu...ic/magpot.html

And here is a lab for you to do: http://physics.bu.edu/ulab/intro1/magnetic.pdf
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 Quote by UltrafastPED See http://hyperphysics.phy-astr.gsu.edu...ic/magpot.html And here is a lab for you to do: http://physics.bu.edu/ulab/intro1/magnetic.pdf

Ok so here is something I don't understand. I've had electricity and magnetism course but I never learned of any such thingn. Why not? Is this stuff told of later on?
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 Ok so here is something I don't understand. I've had electricity and magnetism course but I never learned of any such thingn. Why not?
You'll have to ask the people who taught the courses.
What level was the course taught at?

 Is this stuff told of later on?
I suspect you will already have learned the law of conservation of energy, and the definition of potential energy.
Your course on magnetism should also have taught you about magnetic forces. If those bits are there, you should have been able to figure it out.

 Yes but I know of no equation for potential energy between magnets.
... that does not answer the question I asked: what is the definition of potential energy?

You should have learned that the potential energy of a system is the amount of work needed to get it into that configuration.

You should have equations for the force between two magnets, and an equation for work, and so on.
The course may not have covered magnetic potential energy because the fundamentals had already been taught. After all, how much time will you have for the exam?
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 Quote by Simon Bridge You'll have to ask the people who taught the courses. What level was the course taught at? I suspect you will already have learned the law of conservation of energy, and the definition of potential energy. Your course on magnetism should also have taught you about magnetic forces. If those bits are there, you should have been able to figure it out. ... that does not answer the question I asked: what is the definition of potential energy? You should have learned that the potential energy of a system is the amount of work needed to get it into that configuration. You should have equations for the force between two magnets, and an equation for work, and so on. The course may not have covered magnetic potential energy because the fundamentals had already been taught. After all, how much time will you have for the exam?

Unfortunately I am not sure how to calculate the force between two magnets, only between mag fields and wires
 Homework Sci Advisor HW Helper Thanks P: 12,953 It's similar - permanent magnets are more complicated than bits of wire. You are learning the situations for simple geometries so the maths is easier. i.e. if you have two bar magnets length L which are separated by a distance D>>L, then you can use the magnetic dipole equation. http://en.wikipedia.org/wiki/Force_between_magnets But you can easily tell that there must be a "magnetic potential energy" because you have to do work to push two like poles close to each other. You can get two magnets and measure it.
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 Quote by Simon Bridge It's similar - permanent magnets are more complicated than bits of wire. You are learning the situations for simple geometries so the maths is easier. i.e. if you have two bar magnets length L which are separated by a distance D>>L, then you can use the magnetic dipole equation. http://en.wikipedia.org/wiki/Force_between_magnets But you can easily tell that there must be a "magnetic potential energy" because you have to do work to push two like poles close to each other. You can get two magnets and measure it.

Yeah I mean I was sure there was a pot energy between them but I didn't know the force between them so I couldn't calculate the pot energy between them. Are these equations created empirically?
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 Quote by Simon Bridge It's similar - permanent magnets are more complicated than bits of wire. You are learning the situations for simple geometries so the maths is easier. i.e. if you have two bar magnets length L which are separated by a distance D>>L, then you can use the magnetic dipole equation. http://en.wikipedia.org/wiki/Force_between_magnets But you can easily tell that there must be a "magnetic potential energy" because you have to do work to push two like poles close to each other. You can get two magnets and measure it.

Also I've read the whole giancoli physics based on calc 3 and I've never run into forces between permanent magnets.
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 Quote by jaredvert Yeah I mean I was sure there was a pot energy between them but I didn't know the force between them so I couldn't calculate the pot energy between them. Are these equations created empirically?
That is usually the easiest way to do it in practice - but you can make approximations for simple geometries.
People who make magnets for a living need to be able to predict how strong-a magnet they'll get from a particular process.
I think this is a college level field of materials engineering.

 Quote by jaredvert Also I've read the whole giancoli physics based on calc 3 and I've never run into forces between permanent magnets.
You wouldn't - even though you have probably handled permanent magnets as part of practical demonstrations. At that level, and well into college, permanent magnets are mostly treated qualitatively.

You should have had a little bit on how permanent magnets work, at least in terms of "magnetic domains". There should also be a bit of maths about a magnetic dipole field ... this is the field due to a very small current loop. You can see the analogy between that and the field due to a permanent magnet.

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