a simple magnet
posted by Ragib - March 14 2011 02:24:25 PM
you have two same looking iron rods.but one is weak are in a room where you don't have any compass or you can't distinguish between north,south,east and can you recognise the magnet?keep in mind that it's weak magnet and you can use anything but compass and other metals.
Reply by Caprico - March 14 2011 10:47:25 PM
Exactly how weak is it? Do the iron rods attract slightly? If yes, then I have a sure solution.

Hit one of the iron rods really hard against some surface. Then bring them close.
1)If they still attract, then the one you hit is the iron rod, and the one you didn't is the magnet.
2)If they don't attract, then the one you hit is the magnet.

Now if they don't attract, then here's an idea (though I'm not sure if it would work with weak magnets)

Take one end of one of the iron rods, and stroke the other one in one direction.
1) If the iron rod you took is a magnet, then the other iron rod will also get temporarily magnetized, and one of its ends should repel one end of the original magnet.
2) If the iron rod you took is just an iron rod, then nothing will happen.

Reply by Caprico - March 14 2011 10:54:27 PM
Or here's another idea. Magnets are ineffective at their magnetic center, that is to say, they won't attract ferromagnetic substances at their center. Carry out the obvious experiment, and you'll know which is which...

Reply by Ragib - March 15 2011 06:16:52 AM
don't be so diplomatic.just think easily.hope you know about curie point.a weak magnet would lose its magnetic power while heated up to a certain can use the rod.if it still attracts,then it's rod.and vice versa.i am not sure if hitting magnet would help.but it might be possible.

Reply by Ragib - March 15 2011 06:18:26 AM
depending on how much heat you can give,the riddle if effective for strong magnets too.

Reply by Caprico - March 15 2011 10:47:46 AM
Oh yeah... Nice one... forgot the obvious... :P

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