Re: Opposites.

[brian whatcott <inet@intellisys.net>]

At 08:39 5/5/98 -0700, you wrote:
> > Two oppositely charged particles traveling in opposite directions
> > along parallel paths? Whoops, which kind of "oppositeness" rules?
> [Don Simanek]

> Hah! got tangled in your rules, eh? They attract, of course
>
> Your point is correct; your example is, unfortunately, ill-chosen.
> The reason, of course, is that currents going in the *same*
> direction attract, what is known as the "pinch effect". The pinch
> effect is itself a fine Gegenbeispiel. In that case "Likes attract."
>
> Leigh

I suspect it is Leigh who has been caught. One may accept the pinch 
effect, but then argue like this:
a moving particle does not have to represent a current.
If oppositely charged particles travelling in opposition attract,
then one could assume that similarly charged particles travelling 
in convoy would also attract ( via the double negative ).

 But when one places a charge on two adjacent foils - the current 
soon subsides, but the foils are left displaced - in the prototypical
electrometer, for example.

 I hasten to reassure Leigh that there is a practical example much
more to his taste - a fellow at NASA-Ames came up with a way
to replace the rather cumbersome pneumatic boots which crack ice off
 aircraft wing leading edges, or the considerable power needed to melt
ice with bleed air or electrical resistance tape. 

His method uses a pair of copper tapes laid together but insulated from 
each other except at the end. 
A large (but short term) currrent pulse in such a loop generates huge
accelerations sufficient to easily crack ice accumulations or rather to
pulverize ice coatings entirely to dust.

 The military was so taken with the several thousand g so easily 
obtainable that they encouraged the development of an EM slingshot which
could handily outperform the railgun.

Whatcott    Altus OK