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Bar Magnets

Science brain teasers require understanding of the physical or biological world and the laws that govern it.


Puzzle ID:#1067
Fun:*** (2.59)
Difficulty:** (1.85)
Submitted By:vivek***




You have two bars of iron. One is magnetized along its length, the other is not. Without using any other instrument (thread, filings, other magnets, etc.), find out which is which.

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Jun 05, 2002

You could also throw one of the bars against a solid surface and hold them together to see if the magnetic intensity has degraded. Also repeat with the other bar. Magnetic objects lose their intensity when violently struck.
(user deleted)
Aug 14, 2002

Form a T with the two bars. Then offset one from the middle a little, if it slides to one end, the top one is the magnet, if it doesn't, the bottom one is. Common experiment in physics classes. Very cool.
Jan 10, 2004

Jun 01, 2005

I'm not much sure about this, but I remember reading the same thing in my science textbook when I was in the eighth grade. It had a chapter on magnetism and a similar problem.
Jun 14, 2007

That makes no sense, if they stick together you still don't know which is magnetized. It could be either
Mar 12, 2010

I enjoyed this puzzle. I'd forgotten that bar magnets were dead in the middle but suspected they might be from my memory of the shape of their magnetic fields.

I chose to put the end of bar A very slightly offset from the centre of bar B so that, if bar B was the magnet the (weaker) attraction would move bar A laterally in the direction of the off-centre. If bar A was the magnet then the (stronger) attraction would be directly toward bar B.

Fun quiz. Thanks!
Sep 17, 2016

Bar A will pick up small metal particles on the floor, carpet, even in dirt ground. Bar B will not. Bar A will stick to most iron or steel surfaces. Bar B will not.

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