AI-4
SQUARE MIL—The area of a square, the sides of which are each equal to 1 mil. One square mil is equal to
1.2732 circular mils.
STRANDED CONDUCTOR—A conductor composed of a group of wires. The wires in a stranded
conductor are usually twisted together and not insulated from each other.
STRANDS—Fine metallic filaments twisted together to form a single wire.
TEMPERATURE COEFFICIENT OF RESISTANCE—The amount of increase in the resistance of a 1-
ohm sample of a conductor per each degree of rise in temperature above 0º C.
TENSILE STRENGTH—The greatest stress a substance can withstand along its length without tearing
apart.
TERMINAL—A point of connection for two or more conductors in an electrical circuit.
TERMINAL BOARD—(Also called a terminal strip.) An insulating base or slab equipped with terminals
for connecting wiring.
TERMINAL DIAGRAM—A diagram of a switch, relay, terminal board, or other component showing the
connections to the equipment.
TERMINAL LUG—A device attached to a conductor for connecting to a terminal.
THERMAL INERTIA—The capacity of a soldering iron to generate and maintain a satisfactory soldering
temperature while giving up heat to the material being soldered.
THERMISTOR—A semiconductor device whose resistance varies with temperature.
THERMOPLASTIC—A synthetic mixture of rosins that is flexible and used as an insulating material.
Generally used as an insulator for low- and medium-range voltages.
TINNING—The process of applying a thin coat of solder to materials prior to their being soldered (for
example, application of a light coat of solder to the filaments of a conductor to hold the filaments in
place prior to soldering the conductor).
TOXIC VAPORS—Vapors emitted by a substance that can do bodily harm.
TRANSPARENT TUBING—(Also known as spaghetti tubing.) A plastic tubing used for insulation and
wire marking.
UNIT SIZE—The standards adopted to make comparisons between things of like value (for example, the
unit size for conductors is the mil-foot).
VARNISHED CAMBRIC—Cotton cloth coated with insulation varnish. An insulation used on high-
voltage conductors.
VOLTAGE DROP—The difference in voltage between two points. It is the result of the loss of electrical
pressure as a current flows through a resistance.
WIRE—A solid or stranded group of solid, cylindrical conductors having low resistance to current flow,
with an associated insulation.
WIRE STRIPPERS—A tool used to strip insulation from wire.
