Re: [Phys-L] magnetic field reversals

["John Clement" <clement@hal-pc.org>]

I would think that reversal was caused by an external influence such as
putting them together with another stronger magnet.  Improper storate with
all of the magnets oriented in the same direction might be part of the
problem.  Proper storate is laying them in a triangle or circle with N
against S.  Dropping could cause random reversals, so that the magnet
becomes weaker.  You should not have students use conventional bar magnets
and strong ceramic magnets together because of the possibility of weakening
the bar magnets.

If you have a magnetizer, it is possilbe that the techs or students have
inserted the bars into it randomly.  Old bar magnets do not hold their
magnetism very well, so you have to use a magnetizer fairly frequently on
them.  I would say that mususe of the magnetizer may be a real possibility.
I did not always have access to a magnetizer so I would carefully use
ceramic magnets to "refresh" the bar magnets.

John Clement
Hoston, TX

> > It seems somewhat common to find that bar magnets used in labs get 
> > their magnetization reversed, so the actual poles are opposite the 
> > ones painted on the bar. I am wondering why reversals are so common?