Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] induced electric field



I am not sure what reconciled means here. I am impressed with Bob's solution to the rectangular loop problem - it's one I will file away for future reference. But my comments were directed to a statement of the problem that did not specify a rectangular loop - just a uniform dB/dt presumably over all space - a far less daunting problem than those that have been solved for us so elegantly - but one I nevertheless still claim cannot have a solution without some prefered direction or boundary in space being given.

Bob at PC

________________________________________
From: phys-l-bounces@carnot.physics.buffalo.edu [phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Brian Whatcott [betwys1@sbcglobal.net]
Sent: Thursday, November 26, 2009 4:36 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] induced electric field

I wonder if Bob and Phillip are now reconciled to the beautifully drawn
plots from Bob for the field conditions specified by David?

Brian W

LaMontagne, Bob wrote:
/snip/
I have not assumed that the E field is tangential to the loop. I am only assuming that because no boundaries are stated that no matter where I put the loop the integral (EMF) must be the same because nothing distinguishes one postion of the loop from another./snip/

If a boundary is specified then the symmetry is broken and I agree with you and JD that the field at any point can be easily argued to be unique and can probably be found by some clever argument.

Bob at PC


________________________________________
From: Philip Keller [PKeller@holmdelschools.org

/snip/ suppose you cannot assume that the field has the same magnitude at all points on the loop -- say because it is that second loop you and I were both thinking of, near but not touching the first. At the point where the second loop is nearest the first, the electric field is pointing "the wrong way" - not in the direction of the current. /snip/the problem shows up regularly on the EM section of the AP physics C test but I don't recall symmetry or boundary conditions ever being mentioned.


_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l