Re: B and electric charge

[Jack Uretsky <jlu@HEP.ANL.GOV>]

Dear Professor Kowalski-
        Thank you for telling me about convection currents.  Just
to see how your experiment worked, I rubbed a long plastic tube with
a handkerchief until it was electrified enough to make some scotch tape
move.  Then I waved the tube real hard under a refrigerator magnet that
was suspended by a thread.  The magnet didn't move until I hit it by
accident.  I don't think that's what you meant.
        My friend Linda said that it's the v/c that counts.  But she's
just a girl, so what does she know?  I mean about plastice tubes and
stuff like that.  She's really pretty smart about some things.
                                Your student,
                                        Jack



On Sat, 5 Jan 2002, Ludwik Kowalski wrote:

> In the context of this discussion I would
> focus on a "convection current", for example,
> a long dielectric stick whose charge per
> unit length is known. Measure its speed and
> calculate the current in C/s. Convection
> currents have been studied about a century
> ago and they were shown to produce the
> conventional (expected magnetic effects.
> Ludwik Kowalski
>
> ----- Original Message -----
> From: Jack Uretsky <jlu@HEP.ANL.GOV>
> Date: Saturday, January 5, 2002 11:03 am
> Subject: Re: B and electric charge
>
> >        Here's one waiting for your return:
> >        How about going in baby steps, though, like you're the
> > teacher and
> > I am trying to understand what you are doing (not much of a stretch).
> >        We've agreed on definition of charge, as described previously.
> > The arbitrary constant is 25 N-m^{2}/C^{2}; an equal charge pair
> > givinga force of 1 N at a separation of 1 m is 1/5 C.  Now I hear
> > you talking
> > about currents.  How do I measure a current (I understand that it is
> > "flowing charge" and 1 A = 1 C/s)?
> >        How do you answer your student?
> >                                Regards,
> >                                        Jack
> >
> >
> > On Fri, 4 Jan 2002, Ludwik Kowalski wrote:
> >
> > > Ludwik Kowalski wrote:
> > >
> > > > What I would like to discuss is the definition of B.
> > > > Why do we define it in terms of the EFFECT of the
> > > > magnetic field and not in terms of what CAUSES it?
> > > > Instead of introducing B via the Lorentz law (directly
> > > > or indirectly) we can introduce it via the Bio Savart
> > > > law. Which way is pedagogically more desirable and
> > > > why? I have no opinion so far.

--
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you, because that is what I must do.  Tonight it is only you and me, fish.
It is your strength against my intelligence.  It is a veritable potpourri
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