Re: [Phys-l] induced electric field

[Brian Whatcott <betwys1@sbcglobal.net>]

Me too....

LaMontagne, Bob wrote:
> My response at bottom.
>
> ________________________________________
> John Denker [jsd@av8n.com]d
>
> On 11/17/2009 11:08 AM, Philip Keller wrote:
>   
> > Thank you for the reply -- I will need to read this all more slowly.
> > But for now, I hope this is an easy question.  What happens to an
> > isolated point charge in a region in space with a uniformly
> > increasing uniform mag field?  Does it experience a force?
> >     
>
> Sure.
>
>   
> > If so, in what direction?
> >     
>
> In the same direction as the E field.  F = q E.
> For ordinary not-too-weird-shaped regions, the
> field will be azimuthal, i.e. in the dθ direction.
>
> --------------------------------------
>
> Where is the axis of this azimuth? If the region of dB/dt is very large an symmetric, I don't see how there is a specific direction for E. You could integrate curl E around a path to get an "EMF" , but how do actually identify E or its direction at a particular point?
>
> Bob at PC
>   
Bob makes a good point - it's one that John D essayed to answer with his 
curl versus field response. Let me say it out loud. There is NO linear 
direction for the E field vector
there is only a turning direction - clockwise or a-clockwise ("the curl")

I was not thrilled by the suggestion of a central singularity - this is 
an artifact only of the math.

About the azimuthal term: for a gun-layer and some astronomers, it is 
convenient to specify directions in terms of azimuth and elevation as 
two angles subtended from a reference direction/plane.   These azimuths 
are often called by pilots "radials" as a descriptive term in 
navigation. This is NOT what we are talking about when referencing this 
electric field that has no constant direction, but only a constant 
direction of rotation.
Just a case of being divided by a common language, I'm sure.

Brian W