Re: [Phys-l] current vector

[Bernard Cleyet <bernardcleyet@redshift.com>]

I think Moses can do a better job, but a stab -- your example is like a 
parallel plates cap. connected by a wire.  Here the current and current 
density are identical, except for pinch, skin, size, etc. effects.  So 
I'm stuck -- what's the problem?

bc, maybe doesn't get it

Brian Whatcott wrote:

> Then perhaps bc can do as much for me. If I arrange an air nozzle to discharge
> between two coplanar plates from a central aperture, what is the direction
> associated with the vector air velocity, and the vector air displacement?
>
> I chose this as conceptually congruent with  Moses's  current mind experiment.
>
> Brian Whatcott
>
> At 01:46 AM 2/23/2006, Bernard Cleyet wrote:
>  
>
> > I presume you mean discharge not by a wire connecting the concentric
> > spheres, but by a leaky dielectric.  In which case you have "crystal
> > clarified" the discussion; thank you.
> >
> > bc
> >
> > Fayngold, Moses wrote:
> >
> >    
> >
> > > It looks like the disagreement between John Denker and John Mallinckroft
> > > has been caused by interchangeable use of the two different 
> > >      
> > concepts: current
> >    
> >
> > > and current density. Current (as a rate of charge transfer through a
> > > surface) is not a vector. This can be made crystal clear by considering,
> > > say, electrical discharge of a spherical capacitor. We have non-zero
> > > charge transfer with no direction to single out.
> > > Current density is a vector, about which, I think, there is no
> > > disagreement.
> > >
> > > Moses Fayngold,
> > > NJIT
> > >
> > >
> > > -----Original Message-----
> > > From:  phys-l-bounces@carnot.physics.buffalo.edu on behalf of John 
> > >      
> > Mallinckrodt
> >    
> >
> > > Sent:  Tue 2/21/2006 12:37 PM
> > > To:    Forum for Physics Educators
> > > Cc:
> > > Subject:       Re: [Phys-l] current vector
> > >
> > > John Denker wrote:
> > >
> > >
> > >
> > >      
> > >
> > > > On 2/21/06, John Mallinckrodt <ajm@csupomona.edu> wrote:
> > > >
> > > >        
> > > >
> > > > > While it is true that the notion of current often--as when it flows
> > > > >          
> > > >
> > > >        
> > cut
> > _______________________________________________
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> >    
>
>
> Brian Whatcott    Altus OK    Eureka! 
>
>
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