It is a fallacy, because in neither case do they
neutralize one another. Whichever way the current flows to make the
magnetism, it is opposed in the coils while the current is rising,
and helped in the coils while the current is falling, by the so-called
extra currents. If the current is rising in both coils at the same
moment, then, whether the coils are in series or in parallel, the
effect of self-induction is to retard the rise of the current. The
advantage of parallel grouping is simply that it reduces the time
constant.
BATTERY GROUPING FOR QUICKEST ACTION.
One may consider the question of grouping the battery cells from the
same point of view. How does the need for rapid working, and the
question of time constant, affect the best mode of grouping the
battery cells? The amateur's rule, which tells you to so arrange your
battery that its internal resistance should be equal to the external
resistance, gives you a result wholly wrong for rapid working. The
supposed best arrangement will not give you (at the expense even of
economy) the best result that might be got out of the given number of
cells. Let us take an example and calculate it out, and place the
results graphically before our eyes in the form of curves.
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