Science Buddies: "Ask an Expert"

At home, I rolled up a piece of paper into a tube and wrapped wire around the tube to make a solenoid. I then placed a magnet inside and ran current through the wire. I was expecting for the magnet to simple slide one way or the other, but i seemed to go to the center of the tube or away from the center. Can somebody please explain why that happens? Also, I read that the magnetic force from a charge is perpendicular to both the velocity and the magnetic field of the charge ( http://hyperphysics.phy-astr.gsu.edu/hb ... agfor.html ). So what direction would the magnetic force of a solenoid be in? Would it be outward? Inward?

-Misha

Finding the magnetic polarity of a coil charged with DC is easy if you remember the left hand rule. http://www.tpub.com/basae/11011_files/image042.jpg (which I found on http://www.tpub.com/basae/11.htm) shows it pretty well. The force, if you're comparing it to a standard bar magnet, is really along the axis of the coil center.

I can't explain what you saw with your test, as I would also have expected the magnet to be propelled to one end or the other. You used a battery or some other DC source?

I think there could be complications if the magnet is not well aligned with the long axis of the solenoid.

http://www.aplusphysics.com/courses/hon ... etism.html

Cheers,
CB