Re: Appropriate for Gen Phys? was: comprehending electric/magnetic interactions

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

Is it really necessary to mention energy?  Suppose you place a bar
magnet in a uniform magnetic field (e.g., a compass needle in the
earth's magnetic field).  Is there a net force exerted on the magnet?  I
think a Gen Phys student should be able to answer this without referring
to energy (i.e., the force on each end of the magnet is equal and
opposite in direction).

Or am I missing something?

____________________________________________________
Robert Cohen; 570-422-3428; www.esu.edu/~bbq
East Stroudsburg University; E. Stroudsburg, PA 18301


> -----Original Message-----
> From: Gary Turner [mailto:turner@MORNINGSIDE.EDU] 
> Sent: Thursday, July 03, 2003 3:23 PM
>
> On Wed, 2 Jul 2003 14:00:16 -0700, Bernard Cleyet 
> <anngeorg@PACBELL.NET>
> wrote:
>
> [snipped section on discussion of forces on a current ring in 
> a magnetic field.  A comment was made about the energy not 
> changing in a uniform field so there can be no unbalanced 
> force - see "comprehending electric/magnetic interactions"]
>
> > OK -- I had a serious Sr. moment:   Since the potential is 
> constant the
> > gradient is zero.   Is this above the level of  Turner's class?
> Sounds about the right level to me.  We do discuss the link 
> between forces and potentials in electric and gravity fields. 
>  I haven't previously introduced the potential of a magnetic 
> field specifically, b/c we usually cover magnetic fields in 
> passing and electromagnetism at the end of the semester when 
> time gets more desperate.  Seems obvious now, perhaps I 
> should introduce this in Gen Phys.
>
> Hmmm, any comments?
>
> The reason I struggle with this material is because all of my 
> E&M has been very problem-oriented with the tough math 
> stressed.  I've never taken a course where we worked on the 
> concepts in E&M quite the same way we work on concepts in Gen 
> Phys. I would like to give students a chance to develop these 
> concepts.  Is Gen Phys the right place?