hat this transmitter has a high resistance, say
about the same as the internal resistance, _R_{p}_, of the tube and
also that it can carry as large a current.

Of the current which comes from the generator about one-half goes to
the tube and the rest to the transmitter. If the resistance of the
transmitter is increased it can't take as much current. The coil,
_L_{a}_, however, because of its inductance, tends to keep the same
amount of current flowing through itself. For just an instant then the
current in _L_{a}_ keeps steady even though the transmitter doesn't
take its share. The result is more current for the oscillating tube. On
the other hand if the transmitter takes more current, because its
resistance is decreased, the choke coil, _L_{a}_, will momentarily tend
to keep the current steady so that what the transmitter takes must be
at the expense of the oscillating tube.

That's one way of looking at what happens. We know, however, from Fig.
123 that to get an increase in the amplitude of the current in the
oscillating tube we must apply an increased voltage to its plate
circuit. That is what really happens when the transmitter increases in
resistance and so doesn't take its full share of the current. The
reason is this: When the transmitter resistance is increased the
current in the transmitter decreases. Just for a moment it looks as
though the current in _L_{a}_ is going to decrease. That's the way it
looks to the electrons; and you know what electrons do in an inductive
circuit when they think they shall have to stop. They induce each other
to keep on for a moment. For a moment they act just as if there was
some extra e. m. f. which was acting to keep them going. We say,
therefore, that there is an extra e. m. f., and we call this an e. m.
f. of self-induction. All this time there has been active on the plate
circuit of the tube the e. m. f. of the generator. To this there is
added at the instant when the transmitter resistance increases, the e.
m. f. of self-induction in the coil, _L_{a}_ and so the total e. m. f.
applied to the tube is momentarily increased. This increased e. m. f.,
of course, results in an increased amplitude for the alternating
current which the oscillator is supplying to the transmitting antenna.

When the transmitter resistance is decreased, and a larger current
should flow through the choke coil, the electrons are asked to speed up
in going through the coil. At first they object and du