Same Pole Magnet
Name: Marc De S.
I have been teaching science for 29 years and I found something I find
unable to explain. A student in one of my 8th grade classes brought a magnet to me,
claiming there was something wrong with it. Being skeptical, I asked what could
possibly be wrong with this magnet. He showed me. I have a small cylindrical bar
magnet that has the same pole at either end! This is baffling me and all of my
students. I told them I would find out what is going on. HELP!
Probably it is two smaller magnets glued together N to N or S to S.
At face value this is pretty strange. How did you determine the bar had the same pole at
either end? I could imagine doing this by cementing two poles of a magnet N to N or S to
S with adhesive. Or possibly the N and S poles are radial and not axial. You can get
some further data by placing the bar under a sheet of paper and sprinkle with iron
filings (If you have not done this.).
I can think of two possibilities right off the bat:
One is that you have a quadrupole magnet, two north poles and two south poles. Two
like poles are at the ends and two of the other pole are near the center. See whether
the center of the magnet repels the pole that the ends attract. If so, you probably
have 4-pole magnet. Another possibility is that the cylinder is weak compared to the
magnet with which you test it. Placing a strong magnet near a weak magnet can
temporarily reverse the weak magnet. Place the cylinder in contact with the magnet
it attracts. While in contact, see whether the opposite end of the cylinder still
behaves the same as before. Does it still attract the same pole? If not, the
cylinder is probably reversing. This is what happens to a piece of metal that is not
magnetized. There may be other possibilities, but these are the first two that come to
Dr. Ken Mellendorf
Illinois Central College
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Update: June 2012