Isogonic Map.
A map showing the isogonic lines. On such a map each line is
characterized and marked with the degrees and direction of variation of
the compass upon itself.
Synonym--Declination Map.
Isolated Plant, Distribution or Supply.
The system of supplying electric energy by independent generating
systems, dynamo or battery, for each house, factory or other place, as
contra-distinguished from Central Station Distribution or Supply.
Isotropic.
(Greek, equal in manner.)
Having equal properties in all directions; the reverse of anisotropic,
q. v. Thus a homogeneous mass of copper or silver has the same specific
resistance in all directions and is an isotropic conductor. Glass has
the same specific inductive capacity in all directions and is an
isotropic medium or dielectric. The same applies to magnetism. Iron is
an isotropic paramagnetic substance. (See Anisotropic.) The term applies
to other branches of physics also.
I. W. G.
Contraction for Indian Wire Gauge--the gauge adopted in British India.
J.
Symbol for the unit joule, the unit of electric energy.
Jacobi's Law.
A law of electric motors. It states that the maximum work of a motor is
performed when the counter-electromotive force is equal to one-half the
electro-motive force expended on the motor.
Jewelry.
Small incandescent lamps are sometimes mounted as articles of jewelry in
scarf-pins or in the hair. They may be supplied with current from
storage or from portable batteries carried on the person.
Joint, American Twist.
A joint for connecting telegraph wires, especially aerial lines. Its
construction is shown in the cut. The end of each wire is closely wound
around the straight portion of the other wire for a few turns.
Fig. 203. AMERICAN TWIST JOINT.