# Find the magnet among the two rods

Dilemma

You are taken to a dark room and given two thin long rods - 30 cm long and 1 cm thick. One of them is a permanent magnet and the other is pure iron which is not magnetized.

Both of them are insulated with glass. They weigh the same. The shapes are same too. How can you tell which one of these rods is the magnet? Remember, you can't see anything, and you cannot use anything other than these two rods in your investigation. You are not allowed to break them or remove the insulation either.

Hint

zntargfnerzbernggenpgvirarnegurcbyrfgunavagurzvqqyr

• Why do I get the feeling that the hint is a riddle of its own? Nov 10, 2014 at 21:46
• The hint gives it ALL away [sarcasm] the hint is a puzzle on it's own. Nov 10, 2014 at 21:47
• @Evision I posted my comment and right after yours appeared! We both had the same comment XD Nov 10, 2014 at 21:48
• Excellent! Smithers, release the hounds. Nov 10, 2014 at 21:48
• The hint is encoded in rot13. Nov 11, 2014 at 0:58

For the two rods, place the end against the middle of the other and compare the magnetic attraction. The magnetic rod will be the one with its end against the other's middle with the highest pull.

• It would be nice if you would wrap that answer inside a spoiler tag. Nov 10, 2014 at 21:55
• That would work well if the poles of the magnet are aligned with the long axis of the rod. I believe, however, that it would be possible to have the rod magnetized with the poles running perpendicular to its axis (so the magnetic lines of force would be disks whose plane was likewise perpendicular to the axis). Such a magnet would likely not be anywhere near as strong as one with poles on the long axis, but I believe it could nonetheless be constructed. Nov 10, 2014 at 23:11

Balance each rod in turn at its midpoint on your fingertip. Try this several times for each rod in different orientations. The magnet is the one which will tend to rotate towards the same point (north). You can determine this by feel.

Hint:

magnetsaremoreattractivenearthepolesthaninthemiddle

Magnets are more attractive near the poles than in the middle