Previous Index Next
Page 372
(previous) (Page 000372) (next)
 
3 7 2 FRAGMENTS OF SCIENCE.

needle was attracted in your first experiment; and from
this you may at once deduce the consequence that, after the
steel has been magnetized, the repulsive action of a magnet
must be always less than its attractive action. For the
repulsion is opposed by the inductive action of the magnet
on the steel, while the attraction is assisted by the same
inductive action. Make this clear to your minds, and
verify it by your experiments. In some cases you can
actually make the attraction due to the temporary mag-
netism overbalance the repulsion due to the permanent
magnetism, and thus cause two poles of the same kind
apparently to attract each other. When, however, good
hard magnets act on each other from a sufficient distance,
the inductive action practically vanishes, and the repulsion
of like poles is sensibly equal to the attraction of unlike
ones.

I dwell thus long on elementary principles, because
they are of the first importance, and it is the temptation
of this age of unhealthy cramming to neglect them. Now
follow me a little further. In examining the distribution
of magnetism in your strip of steel, you raised the needle
slowly from bottom to top, and found what we called a
neutral point at the centre. Now does the magnet really
exert no influence on the pole presented to its centre ?

Let us see.
FIG. 1.

 

 

 

Sr .N‘

 

 

Let S N, Fig. 1, be your magnet, and let 72 represent a
particle of north magnetism placed exactly Opposite the

Previous Index Next