The magnets are constantly attracting and pushing the wires which are magnetized becuase of the eletricity running through it, thus makes the wire turn...
You can put it on the side and if its strong enough... It can roll forward or backwards, it depends.
For more information visit:http://sci-toys.com/scitoys/scitoys/electro/homopolar/homopolar.html
For more projest please visit:http://www.scitoys.com
I hope you have fun.