Insulating Varnish.
Varnish used to coat the surface of glass electrical apparatus, to
prevent the deposition of hygrometric moisture, and also in the
construction of magnetizing and induction coils and the like. Shellac
dissolved in alcohol is much used. Gum copal dissolved in ether is
another. A solution of sealing wax in alcohol is also used. If applied
in quantities these may need baking to bring about the last drying. (See
Shellac Varnish.)
Insulator.
(a) Any insulating substance.
(b) A telegraph or line insulator for telegraph wires. (See Insulator,
Line or Telegraph.)
Synonyms--Dielectric--Non-conductor.
Insulator Cap.
A covering or hood, generally of iron, placed over an insulator to
protect it from injury by fracture with stones or missiles.
Insulator, Fluid.
(a) For very high potentials, as in induction coils or alternating
circuits, fluid insulators, such as petroleum or resin oil, have been
used. Their principal merit is that if a discharge does take place
through them the opening at once closes, so that they are self-healing.
(b) Also a form of telegraph or line insulator in which the lower rim is
turned up and inwards, so as to form an annular cup which is filled with
oil.
Insulator, Line or Telegraph.
A support often in the shape of a collar or cap, for a telegraph or
other wire, made of insulating material. Glass is generally used in the
United States, porcelain is adopted for special cases; pottery or stone
ware insulators have been used a great deal in other countries.
Sometimes the insulator is an iron hook set into a glass screw, which is
inserted into a hole in a telegraph bracket. Sometimes a hook is caused
to depend from the interior of an inverted cup and the space between the
shank of the hook and cup is filled with paraffine run in while melted.
Insulators are tested by measuring their resistance while immersed in a
vessel of water.
Intensity. Strength.
The intensity of a current or its amperage or strength; the intensity or
strength of a magnetic field or its magnetic density; the intensity or
strength of a light are examples of its use. In the case of dynamic
electricity it must be distinguished from tension. The latter
corresponds to potential difference or voltage and is not an attribute
of current; intensity has no reference to potential and is a
characteristic of current.
Intensity of a Magnetic Field.
The intensity of a magnetic field at any point is measured by the force
with which it acts on a unit magnet pole placed at that point. Hence
unit intensity of field is that intensity of field which acts on a unit
pole with a force of one dyne. (S. P. Thomson.) (See Magnetic Lines of
Force.)