Accumulator material is sulphuric acid, diluted with water.

Active Material

That part of the material in accumulator plates which is acted upon by the electric current.


A cell, generally known as a storage battery, which while it initially receives a charge of electricity, is nevertheless, of such a character, owing to the active material of which it is made, that it accumulates, or, as it were, generates electricity.

Aerial Wire, or Conductor

The wire which, in wireless telegraphy, is carried up into the air to connect the antennæ with the receiving and sending apparatus.

Alarm, Burglar

A circulating system in a building, connected up with a bell or other signaling means.


A mixture of two or more metals; as copper and zinc to make brass; nickel and zinc to form German silver.

Alternating Current

A current which goes back and forth in opposite directions, unlike a direct current which flows continuously in one direction over a wire.


The term applied to a change in the direction of an alternating current, the frequency of the alternations ranging up to 20,000 or more vibrations per second.


A resin, yellow in color, which when rubbed with a cloth, becomes excited and gives forth negative electricity.


An instrument for measuring the quantity or flow of electricity.


The unit of current; the term in which strength of the current is measured. An ampere is an electromotive force of one volt through a resistance of one ohm.


A device which indicates or signals a call given from some distant point.


The positive terminal in a conducting circuit, like the terminal of the carbon plate in a battery. It is a plate in an electroplating bath from which the current goes over to the cathode or negative plate or terminal.


A term employed to designate the gap, or the current which flows across between the conductors, like the space between the two carbons of an arc lamp, which gives the light.


A body of iron, or other suitable metal, which is in the magnetic field of a magnet.

Armature Bar

The piece which holds the armature. Also one of a series of bars which form the conductors in armature windings.

Armature Coil

The winding around an armature, or around the core of an armature.

Armature Core

The part in a dynamo or motor which revolves, and on which the wire coils are wound.

Astatic (Galvanometer)

That which has no magnetic action to direct or divert anything exterior to it.


The ultimate particle of an elementary substance.


That property of matter which causes particles to adhere, or cohere, to each other. It is known under a variety of terms, such as gravitation, chemical affinity, electro-magnetism and dynamic attraction.