Re: [Phys-l] EM, is it energy

[Bernard Cleyet <bernardcleyet@redshift.com>]

Now I am puzzled.

'So if there is nothing under the influence of a field, regardless of field 
strength, there is no energy stored in the field."

Appears to contradict:

"Attributing energy to the field rather than to an object influenced by the 
field is something worthwhile which I can pass on to my students."



Where is the energy required to initiate the current loop in a 
superconductor.  If the loop is cut what happens to the energy?

A more easily realized example is air core inductor.  Energy is required 
to initiate the current, yes?, and then additional continuously, because 
of the dissipation.  Again where did the energy come from that is 
transported to, for example a radiated wave when the circuit is broken?

bc fullove questions.



Craig & Margaret Lucanus wrote:

> Attributing energy to the field rather than to an object influenced by the 
> field is something worthwhile which I can pass on to my students. So if 
> there is nothing under the influence of a field, regardless of field 
> strength, there is no energy stored in the field. Thanks JB, this is 
> something I must have missed in text books, or at least it wasn't put that 
> way. This a helpful list.
>
> ----- Original Message ----- 
> From: "John Barrer" <forcejb@yahoo.com>
> To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
> Sent: Sunday, December 02, 2007 1:12 AM
> Subject: Re: [Phys-l] EM, is it energy
>
>
>  
>
> > --- Craig & Margaret Lucanus <lucanus@iinet.net.au>
> > wrote: SNIP
> >
> > or when a book on a
> >    
> >
> > > shelf falls and loses PE,
> > >      
> > This seems to imply that the book "has" PE. Not so. In
> > the book/Earth system (one always needs to define the
> > system when analyzing energy changes), the work done
> > by raising the book to the shelf results in an
> > increase of energy stored in the Earth's gravitational
> > field.
> >
> > It may also be helpful to remember that since
> > computation of system energy is always reference
> > frame-dependent, the only thing that really matters is
> > CHANGE in the energy of a system.
> >
> > John Barrere
> > Fresno Unified School District
> > _______________________________________________
> > Forum for Physics Educators
> > Phys-l@carnot.physics.buffalo.edu
> > https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l 
> >    
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