Re: [Phys-L] Lenz's law and conservation of energy

[Bernard Cleyet <bernard@cleyet.org>]

Huh?!!!

momentum is conserved when E isn’t.  

bc appeal’s to Wiki., which is sometimes dangerous.

Lenz's law /ˈlɛntsɨz lɔː/ is a common way of understanding how electromagnetic circuits obey Newton's third law and the conservation of energy.[1] Lenz's law is named after Heinrich Lenz, and it says:
An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.
Lenz's law is shown with the negative sign in Faraday's law of induction:
Lenz's law - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Lenz%27s_law

Aren’t all true, but only d is relevant?




On 2014, Mar 30, , at 02:58, Dr. Keith S. Taber <kst24@cam.ac.uk> wrote:

> Would (a) be a better answer?
>
> Keith
>
>
> > Hi,
> >
> > I saw an exam question (actually a specimen paper question) which asked:
> >
> > Lenz's law is a consequence of the following concervation principle:
> >
> > a) momentum
> > b) charge
> > c) current
> > d) energy.
> >
> > Naturally, the only choice making sense is d). However, is it really so that Lenz's law is *consequence* of conservation of energy from the poiint of view em-theory? I would rather say that Lenz's law is consistent with conservation of energy (well, what wouldn't be :-)).
> >
> > Any ideas?
> >
> > Regards,
> >
> > Antti
> > --
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> >
> >
> >
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> -- 
>
>
>
> Dr. Keith S. Taber
>
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