Test for polarity of a magnet
The polarity of any magnet may be tested by bringing both its poles, in turn, near to the known poles of a suspended magnet. Repulsion will indicate similar polarity. If attraction occurs, no firm conclusion can be drawn, since attraction would be obtained between either:
(a) two unlike poles or
(b) a pole and a piece of magnetized material.
Repulsionis, therefore, the only sure test for polarity.