Ball-Bearing Motor: Does Heat or EM Force Work?

[karpmage]

Just throwing it out there. What is your take on this? Do you think it works due to heat expansion and contraction, or due to electromagnetic forces? It was involved in one of my questions for IYPT last year and our group is still clueless about it. It seems like neither explanation is accepted yet, so I'd like to see what you guys think it is the right one.

 

[Simon Bridge]

You mean one of these:
http://en.wikipedia.org/wiki/Ball_bearing_motor
?

Most recent peer-reviewed, empirical, research appears to support the EM-only model but does not rule out a contribution from thermal effects.