=Absolute.= Complete by itself. In quantities it refers to fixed units. A galvanometer gives absolute readings if it is graduated to read direct amperes or volts. An absolute vacuum is one in which all residual gases are exhausted; an absolute void is the theoretical consequent. The absolute unit of current is measured in one, two, three, or more amperes or volts. =A-C.= An abbreviation expressing alternating current. =Acceleration.= The rate of change in velocity. The increase or decrease of motion when acted upon by the electric current. =Accumulator.= A term applied to a secondary battery, commonly called a storage-battery. =Accumulator, Electrostatic.= (_See_ Electrostatic Accumulator.) =Accumulator, Storage.= A storage-battery. =Acid.= A compound of hydrogen capable of uniting with a base to form salts. Sour, resembling vinegar. A sharp, biting fluid. =Acidometer.= A hydrometer used to determine the gravity of acids. It is employed chiefly in running storage-batteries to determine when the charge is complete. =Adapter.= A screw-coupling to engage with different size screws on either end, and used chiefly to connect incandescent lamps to gas-fixtures. =Adherence.= The attraction between surfaces of iron due to electro-magnetic action. The term is used in connection with electric brakes--electro-magnetic adherence. =Adjustment.= Any change in an apparatus rendering it more efficient and correct in its work. =Aerial Conductor.= A wire or electric conductor carried over housetops or poles, or otherwise suspended in the air, as distinguished from underground or submarine conductors. =Affinity.= The attraction of atoms and molecules for each other, due to chemical or electrical action. =Air-condenser.= A static condenser whose dielectric is air. =Air-line Wire.= In telegraphy that portion of the line-wire which is strung on poles and carried through the air. =Alarm, Burglar.= A system of circuits with an alarm-bell, the wires of which extend over a house or building, connecting the windows and doors with the annunciator. =Alarm, Electric.= An appliance for calling attention, generally through the ringing of a bell or the operating of a horn. =Alarm, Fire and Heat.= An expansion apparatus that automatically closes a circuit and rings a bell. =Alive, or “Live.”= A term applied to a wire or circuit that is charged with electricity. A “live” wire. Active circuits or wires. =Alloy.= Any mixture of two or more metals making a scientific compound. For example: copper and zinc to form brass; copper, tin, and zinc to form bronze; copper, nickel, and zinc to form German-silver. =Alternating Current.= (_See_ Current, Alternating.) =Alternating Current-power.= Electrical distribution employing the alternating current from dynamos or converters. =Alternation.= A change in the direction of a current; to and fro. Alternations may take place with a frequency ranging from 500 to 10,000 or more vibrations per second.