On Wed, 01 Aug 2007 10:42:35 -0700, Don Stauffer in Minnesota wrote:

On Aug 1, 9:48 am, _
wrote:
I'm thinking of how to make a small clutch and was wondering if putting a
sheet of aluminium between a rotating magnet and a steel plate would
decrease the distance they would need to be separated for the same drag.

Seems to me it would WEAKEN the field. Conducting non-ferrous metals
actually provide some shielding of varying fields.

If the field is varying then a conductor will block the variation -- the
varying field generates eddy currents which set up opposing fields.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html