[Illustration: Fig. 30. Line with Shunt Capacity]

A simple test will enable two of the results of a short-circuiting
capacity to be appreciated. Conceive a very short line of two wires to
connect two local battery telephones. Such a line possesses
negligible resistance, inductance, and shunt capacity. Its insulation
is practically infinite. Let condensers be bridged across the line,
one by one, while conversation goes on. The listening observer will
notice that the sounds reaching his ear steadily grow less loud as the
capacity across the line increases. The speaking observer will notice
that the sounds he hears through the receiver in series with the line
steadily grow louder as the capacity across the line increases. Fig.
31 illustrates the test.

The speaker's observation in this test shows that increasing the
capacity across the line increased the amount of current entering it.
The hearer's observation in this test shows that increasing the
capacity across the line decreased the amount of energy turned into
sound at his receiver.

[Illustration: Fig. 31. Test of Line with Varying Shunt Capacity]

The unit of electrostatic capacity is the _farad_. As this unit is
inconveniently large, for practical applications the unit
_microfarad_--millionth of a farad--is employed. If quantities are
known in microfarads and are to be used in calculations in which the
values of the capacity require to be farads, care should be taken to
introduce the proper corrective factor.