Dielectric.
A non-conductor; a substance, the different parts of which may, after an
electric disturbance, remain, without any process of readjustment, and
for an indefinite period of time, at potentials differing to any extent
(Daniell). There is no perfect dielectric. The term dielectric is
generally only used when an insulator acts to permit induction to take
place through it, like the glass of a Leyden jar.
Dielectric Constant.
The number or coefficient expressing the relative dielectric capacity of
a medium or substance. (See Capacity, Specific Inductive.)
Dielectric, Energy of.
In a condenser, the conducting coatings are merely to conduct the
current all over the surface they cover; the keeping the electricities
separated is the work of the dielectric, and represents potential energy
which appears in the discharge. The amount of energy is proportional to
the charge, and to the potential difference. As any electrified body
implies an opposite electrification somewhere, and a separating
dielectric, the existence of a condenser is always implied.
[Transcriber's note: The energy stored in a capacitor (condenser) is
(Q*Q)/2C = (Q*V)/2 = (C*V*V)/2
The energy is proportional to the voltage SQUARED or the charge SQUARED.]
Dielectric Polarization.
A term due to Faraday. It expresses what he conceived to be the
condition of a dielectric when its opposite faces are oppositely
electrified. The molecules are supposed to be arranged by the
electrification in a series of polar chains, possibly being originally
in themselves seats of opposite polarities, or having such imparted to
them by the electricities. The action is analogous to that of a magnet
pole on a mass of soft iron, or on a pile of iron filings.
Dielectric Strain.
The strain a solid dielectric is subjected to, when its opposite
surfaces are electrified. A Leyden jar dilates under the strain, and
when discharged gives a dull sound. The original condition is not
immediately recovered. Jarring, shaking, etc., assist the recovery from
strain. The cause of the strain is termed Electric Stress. (See Stress,
Electric.) This is identical with the phenomenon of residual charge.
(See Charge, Residual.) Each loss of charge is accompanied with a
proportional return of the dielectric towards its normal condition.
Dielectric Resistance.
The mechanical resistance a body offers to perforation or destruction by
the electric discharge.
Dielectric Strength.
The resistance to the disruptive discharge and depending on its
mechanical resistance largely or entirely. It is expressible in volts
per centimeter thickness. Dry air requires 40,000 volts per centimeter
for a discharge.