d pull, that is on its e. m. f., and upon how
much capacity the condenser has.

[Illustration: Fig 47c]

Remove the battery and connect the charged condenser to the resistance
as in Fig. 47c. The electrons rush home. They bump and jostle their way
along, heating the wire as they go. They have a certain amount of energy
or ability to do work because they are away from home and they use it
all up, bouncing along on their way. When once they are home they have
used up all the surplus energy which the battery gave them.

Try it again, but this time, as in Fig. 47d, connect the charged
condenser to a coil which has inductance. The electrons don't get
started as fast because of the inductance. But they keep going because
the electrons in the wire form the habit. The result is that about the
time enough electrons have got into plate 2 (which was positive), to
satisfy all its lonely protons, the electrons in the wire are streaming
along at a great rate. A lot of them keep going until they land on this
plate and so make it negative.

[Illustration: Fig 47d]

That's the same sort of thing that happens in the case of the inductance
and condenser in the oscillating audion circuit except for one important
fact. There is nothing to keep electrons going to the 2 plate except
this habit. And there are plenty of stay-at-home electrons to stop them
as they rush along. They bump and jostle, but some of them are stopped
or else diverted so that they go bumping around without getting any
nearer plate 2. Of course, they spend all their energy this way, getting
every one all stirred up and heating the wire.

Some of the energy which the electrons had when they were on plate 1 is
spent, therefore, and there aren't as many electrons getting to plate 2.
When they turn around and start back, as you know they do, the same
thing happens. The result is that each successive surge of electrons is
smaller than the preceding. Their energy is being wasted in heating the
wire. The stream of electrons gets smaller and smaller, and the voltage
of the condenser gets smaller and smaller, until by-and-by there isn't
any stream and the condenser is left uncharged. When that happens, we
say the oscillations have "damped out."

[Illustration: Fig 48]

That's one way of starting oscillations which damp out--to start with a
charged condenser and connect an inductance across it. There is another
way which leads us to some important ideas. Look at Fig. 48. T