Any method of obtaining measurements or comparisons, in which the
measurement is correct when the deflection of the galvanometer or other
indicator is zero, nought or null. The Wheatstone Bridge (see Bridge,
Wheatstone) is an example of a null method.
Two obvious advantages attach to null methods in electric galvanometer
work. One is that an uncalibrated galvanometer can be employed. [...]

The pole of a magnet which tends to point to the north; the north pole
of a magnet.

(a) The north-seeking pole of a magnet; the pole of a magnet which tends
to point to the north, and whence lines of force are assumed to issue on
their course to the other pole of the magnet.
(b) The North Pole of the earth. Treating the earth as a magnet, and
accepting the above nomenclature the north pole [...]

A material that does not conduct electricity except with great
difficulty; a substance of very high resistance.
Synonym–Insulator–Dielectric.

A deposit obtained in electroplating, characterized by irregular
thickness; due to too low density of current.

When a dilute solution of copper acetate is placed on a bright silver
plate and a strip of zinc is touched to the silver beneath the copper, a
series of rings of copper are formed by electrolysis around the zinc.
These are Nobili’s rings.
If for the copper acetate a solution of lead oxide in potassium hydrate
solution is substituted, [...]

An alarm bell in a telegraph office, which bell is connected at night to
give a loud signal to attract the operator’s attention. It is used in
telephone exchanges and is connected so as to ring as long as a
subscriber remains unanswered after calling.

A bath for the electro-deposition of nickel. A great many
formulae have been given. Metallic nickel is dissolved in 1 vol.
sulphuric acid mixed with 2 vols. water. Neutralize with ammonia, and
add of ammonium sulphate one-half the weight of metallic nickel
originally used; 135 parts of nickel will be enough for a bath of 10,000
parts.
Other formulae are as [...]

A metal; one of the elements; atomic weight, 58.8 ; equivalent, 29.4;
valency, 2; specific gravity, 8.8. It is a conductor of electricity.
Relative resistance, annealed (Silver = 1),   8.285 Specific Resistance,                         12.47   microhms. Resistance of a wire (a) 1 foot long, weighing 1 grain,      15.206   ohms. (b) 1 foot long, 1/1000 inch [...]

Symbol or contraction for “nominal horse power.” This is a basis for
rating the size of an engine.