Re: B and electric charge

[Ludwik Kowalski <kowalskil@MAIL.MONTCLAIR.EDU>]

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.
> >
> > Actually the question should have been asked differently.
> > Why do we first show what the field does and then how
> > it is produced? In other words, why Lorentz first and
> > Biot-Savatr later? Would the reversal be desirable or not?
> > The formal introduction of B should match the conceptual
> > sequence chosen, as it does in most textbooks.
> > Ludwik Kowalski
>
> --
> "But as much as I love and respect you, I will beat you and I will
> killyou, 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
> potpourriof metaphor, every nuance of which is fraught with meaning."
>                     Greg Nagan from "The Old Man and the Sea" in
>                     <The 5-MINUTE ILIAD and Other Classics>