Tina: The apparatus I described was sold by Sargent Welch. Look in
their catalog. Next have your student try to emulate the design. In
principle, it is nothing more than one fixed wire (bottom wire) with
another moveable wire set up as 3/4 of a loop (in the shape of a
rectangular "U"). the 1st and last sections are the pivot arms, and
the middle section rides above the bottom wire. Its just a torque
device. The purpose of using this configuration is that it is very
stable.
The next, most obvious aspect, is that as long as the separation is
small, the force does not have to be large (so the currents can be
smaller). After all, you are just levitating the mass of the wire
with the F=iLB with B from the "bottom wire" being mu*i/2*pi*r, where
r is the distance of separation.
Look at the apparatus. I think its doable...Karl
--
Dr. Karl I. Trappe Desk (512) 471-4152
Lecture Demonstration Office Office (512) 471-5411
Physics Department, Mail Stop C-1600 Home (512) 264-1616
The University of Texas at Austin
Austin, Texas 78712-1081