Science brain teasers require understanding of the physical or biological world and the laws that govern it.
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.
Bar magnets are "dead" in their centers (i.e., there is no magnetic force, since the two poles cancel out). So, if bar A is the magnet, then bar B won't stick to its center.
However, bar magnets are quite "alive" at their edges (i.e., the magnetic force is concentrated). So, if bar B is the magnet, then bar A will stick nicely to its end.
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. |
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!
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