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?

(In reply to Solution by Penny)

I don't agree with the solution of magnetizing one end of the iron bar.  That leaves you with the following two bars, presuming it was the North ends you were rubbing together:

NNNNSSSS  and NNNN----

If you then take the North end of either one of those and hold it perpendicular toward the center of the other, you'll find it repels the left side and attracts the right side. 

Likewise, if you hold the "South" (or "Neutral") sides of either bar in a similar fashion, you'll find that it attracts both the left and the right side of the other bar.

I'm therefore not certain how your solution works.  Can you elaborate?

Posted by John on 2005-01-25 16:24:20