ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
that can he held by the container. A capacitor with the large
plate area can store more charges than a capacitor with a small
plate area. Simply stated, "the larger the plate area, the
larger the capacitance."
(2) The Distance Between the Plates. The second factor
affecting capacitance is the DISTANCE BETWEEN THE PLATES.
Electrostatic lines of force are strongest when the charged
particles that create them are close together. When the charged
particles are moved further apart, the lines of force weaken,
and the ability to store a charge decreases.
(3) The Dielectric. Constant of the Material Between the
Plates. The third factor affecting capacitance is the
DIELECTRIC CONSTANT of the insulating material between the
plates of a capacitor. The various insulating materials used as
the dielectric in a capacitor differ in their ability to respond
to (pass) electrostatic lines of force. A dielectric material,
or insulator, is rated as to its ability to respond to
electrostatic lines of force in terms of a figure called the
DIELECTRIC CONSTANT. A dielectric material with a high
dielectric constant is a better insulator than a dielectric
material with a low dielectric constant. Dielectric constants
for some common materials are given in the following list:
Material
Constant
Vacuum
1.0000
Air
1.0006
Paraffin Paper
3.5
Glass
5 to 10
Mica
3 to 6
Rubber
2.5 to 35
Wood
2.5 to 8
Glycerin (15 C)
56
Petroleum
2
Pure Water
81
Notice the dielectric constant for a vacuum. Since a vacuum is
the standard of reference, it is assigned a constant of one.
The dielectric constants of all materials are compared to that
of a vacuum. Since the dielectric constant of air has been
determined to be approximately the same as a vacuum, the
dielectric constant of AIR is also considered to be equal to one.
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