Re: Can a magnetic field do work?
- From: "Androcles" <Headmaster@xxxxxxxxxxxxxxxx>
- Date: Tue, 16 Sep 2008 23:13:24 +0100
"Cwatters" <colin.wattersNOSPAM@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:hf6dnVdn3uSzg03VnZ2dneKdnZzinZ2d@xxxxxxxxxxxxxxxxx
"Edward Green" <spamspamspam3@xxxxxxxxxxx> wrote in message news:b17b7a94-f5fa-41dd-ba7c-44c034a5db4c@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Sep 15, 4:40 pm, "Cwatters"
<colin.wattersNOS...@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:"marcus_b" <marcus_bruck...@xxxxxxxxx> wrote in message
news:81b76f08-6bd2-4eaf-b49c-bf8af1221bbd@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> -- The permanent magnet did not do work. It didn't even move.
Yes it did. It moved relative to the iron block.
We are always free to exam a system from a fixed reference frame, and
in particular, one in which the magnet is at rest. I suppose we would
say that the magnetic field is doing the work
Work requires energy right. Since energy cannot be created (or distroyed) there is no such thing as a "source of energy". All sources of energy are really just energy stores in one form or another. The energy required to lift the block was stored in the _system_ comprising the magnetic field and iron block when it was created. It doesn't make sense to ask which part of that system did the work.
The block was not lifted, it fell onto the magnet. It will take more than the
gravitational pull of the Earth to lift it off again.
.
- References:
- Can a magnetic field do work?
- From: marcus_b
- Re: Can a magnetic field do work?
- From: Cwatters
- Re: Can a magnetic field do work?
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- Re: Can a magnetic field do work?
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