68 
Magnetic Induction in an Elongated Spheroid, 
or linear density of induced magnetism in a long thin cylinder 
due to a coil embracing half its length is constant. 
6. The formula being thus experimentally verified, it may 
obviously be used to find how the value of k corresponding 
to different values of current, varies. 
For this the small coil was placed in the central position 
and the throws of the galvanometer for different values of 
the current were noted. The following table gives the 
results of experiment. 
Current in amperes. 
Throw. 
•2 
1-05 
•4 
2\1 
•6 
3-15 
•8 
4-4 
1 
G 
1-2 
7-04 
i-4 
8-07 
1-6 
9*2 
1-8 
10-02 
9 
11-55 
These throws are plotted on a curve (fig. 3) in which these 
Fig. 
3. 
. 
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1 
T 
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are abscissae and the currents are ordinates. We see that 
up to current of *8 ampere k is absolutely constant, and then 
begins to vary slightly with the current, the variation being at 
first inappreciable. Unfortunately, however, the effect of the 
current in heating the coil as well as the rod was so great 
when the current was over 2 amperes, that it was not thought 
desirable to proceed with the experiments for stronger 
currents without considerable modification in the apparatus. 
I have to thank Prof. Trouton for permission to work at 
the University College Laboratory for the purposes of the 
above investigation. 
