You have two identical looking metal bars. One of them is a magnet, with North and South ends. The other is simply an iron bar (which is attracted by magnets).

How can you tell which is which, using only these two bars?

Although I'm an amateur at differentiating between iron bars and magnets, I'd probably take the following approach:

If I am strong enough to break iron, I would break one of the bars in half.  If the ends attract one another, it's the magnet.  If not, it's the iron bar.

"Barring" that (forgive me), I would probably try to stick the end of one bar toward the dead center of the long side of the other bar.  If it attracts it without moving to one side, then I am holding the magnet.  If it shifts slightly away from the center, then I am holding the iron bar.  I admit, this assumes the magnet is physically semetrical with respect to polarization.

A variation of this would be to stand one bar upright and place the other horizontally on top of it such that it might spin and orient itself as a compass, if it is the magnet.

I'd considered attempting to magnetize the iron bar by rubbing one end of each bar together for an hour.  However, I can't follow that thought up with a suggestion regarding how that would help me determine which is which.

Looking forward to reading other peoples' solutions now.  I'll probably be chiding myself in a minute! :-)

Posted by John on 2005-01-25 16:06:37