consequently increased in the same ratio. Hence the dynamo, with its
maximum load, must revolve at 588 revolutions per minute, and exert a
couple of forty-seven foot-pounds. Let E be the potential of the
conductor from which the current is drawn, measured in volts, C the
current in amperes, and E1 the E.M.F. of the dynamo. Then E1 is
proportional to the product of the angular velocity, and a certain
function of the current. For a velocity [omega], let this function be
denoted by _f_(C). If the characteristic of the dynamo can be drawn,
then _f_(C) is known.

We have then

w
E1 = -------- f
[Omega] (1.)

If R be the resistance in circuit by Ohm's law,

E - E1
C = --------
R

w
= E ------- f(C)
[Omega]
----------------
R

and therefore