Re: FUN: high-speed electrostatic air-threads

["Steven T. Ratliff" <str@nwc.edu>]

On 16 Jun 1998, Bill Beatty wrote:

[regarding the pinch effect]

> I considered that, but pinch cannot reverse the expansion of alike
> charges unless they are in a net neutral volume, right?  The pinch
> effect might squeeze the current in a neutral conductor where there
> are equal - and + charges, but for a charged particle stream, e.g. 
> an electron beam, it would just slow the outward expansion.  When 
> charged air flows from a needle, can the pinch effect squeeze it 
> into a filament, or would the air stream act more like an electron 
> beam?

In the pinch effect you have a radially inward force due to the 
interaction of the current the azimuthal  magnetic field that it 
creates.  The force is in the direction J x B, where J is the current 
density and B is the magnetic field.  It doesn't always just slow the 
outward expansion, but can squeeze the current also.

Sincerely,
Steven Ratliff




Steven T. Ratliff
Associate Professor of Physics
Northwestern College
3003 Snelling Av. N.
Saint Paul, MN  55113-1598

Internet:  stratliff@nwc.edu (or str@nwc.edu)