You can scroll on the bar or click the appropriate letter to find what you would like. Aggregate A mixture of several materials. For example, an aggregate of gravel, mud, natural sand, and crushed stone is used for making concrete. Alloy Substance that has metallic properties and consists of two or more elements; usually at least one is a metal. Alternator A type of alternating-current generator. Ammeter An instrument that measures the strength of an electric current in amperes. Annealing The process of making glass, metal, or allow less brittle by exposing it to heating and then cooling. Cantilever A beam or other horizontal member supported on only one end. Cathode The negative terminal of an electric current system. In a vacuum tube, the filament serves as the cathode or source of electrons that are emitted. Cathode-Ray Tube A tube in which an electron beam is directed across a fluorescent tube in order to generate images. CRTs are used in oscilloscopes, radar, television sets, and computer monitors. Circuit A line of conductors and other electrical devices along which an electrical current flows. A closed circuit allows the current to travel through all devices. If the circuit is broken at some point so that the current cannot flow, it is called an open circuit. Coil A turned wire used to introduce inductance into an electrical circuit. Current The flow of electricity. Metals are good conductors of electric current. Diode A tube with two electrodes; the main use of diodes is to keep the electric current flowing in one direction. Dynamo A type of generator; usually a direct-current generator. It converts energy of mechanical motion into electric current. See also alternator. Elasticity The ability of an object or material to return to its original size and shape, after being pushed or pulled by an outside force. For example, rubber is elastic. Electrode A rod, plate, or wire that is used to conduct electric current out of or into any device. Electromagnet A coil with a soft iron core that acts as a magnet when an electric current is passed through it. Electromotive Force The force that moves an electric current around a circuit. For example, a generator produces an electromotive force. Engine A machine that applies power to do work. It converts various forms of energy into mechanical force and motion. Expansion Joint A space left in structures or roads that allows for the expansion and contraction of the material, caused by heating and cooling of the surrounding environment. Filament A metallic wire that is heated in an incandescent lamp in order to produce light. Fuse A safety device that protects a circuit from receiving too much current. The fuse's wire melts in response to too much electric current passing through it, thus breaking the circuit. Galvanometer An instrument that detects, measures, and determines the direction of a small electric current. Gasket A deformable material, usually a ring of plastic or metal, that is used to make a pressure tight joint between two (usually stationary) parts. Generator A machine that converts mechanical energy into electrical energy. Girder A large beam of wood, metal, or concrete, usually found in skyscrapers and other large buildings. It is used for structural support. Insulator A device with high resistance to heat, electricity, or sound; for example, and electrical insulator prevents electricity from sending current to other objects. Lubricant A substance applied to a surface to reduce friction. Machine A device that helps to do work. Most machines either overcome a force or change the direction of the applied force. Microphone A device that acts as a transformer and amplifier of sound waves into electric currents. Motor A machine that converts electrical energy into mechanical energy. Oscilloscope An instrument that produces an image of varying electrical voltages on a cathode-ray tube. Polymer Large molecules made up of a series of molecular units, similar to beads on a string. Natural polymers include rubber, wool, and cotton; synthetic polymers include nylon and polythene. Polymers are often called giant molecules. Pulley A wheel over which a rope, chain, or wire passes. Pulleys are used to ease the pulling of objects or lifting of heavy weights. Pulley System An arrangement of two or more pulleys that form a machine. Radar (radio detection and ranging) An instrument in which a cathode-ray tube receives reflected radio waves to detect distant objects. Radio A system of transmitting sound signals (as electric impulses) through the air using electromagnetic waves. Receiver A device that transforms radio waves and translates them mainly into sounds or pictures. Relay A device that controls a large electrical current along another circuit by switching on or off. The relay uses a small electric current to control the larger current. Resistor A device that resists an electric current. Rheostat See variable resistor. Stator A stationary machine part about which a rotor turns. Switch A device that is used to switch parts of a circuit on or off. When the switch is on, the electric current is flowing through; when the switch is off, the electric current is cut off. Television A system for transmitting video and audio signals using electromagnetic waves. A television uses a cathode-ray tube to produce images built from 625 constantly changing lines, each of which contains 400 small dots of light. Thermocouple Shortened term for thermoelectric couple. Thermoelectricity The production of an electric current directly from heat, or the reverse. Transformer A device that changes the voltage of an alternating current. Transformers are used to modify the high voltage received from power lines so that it can be used by homes that require lower voltage for electrical devices. Tube (or valve) An electrical device that allows electric current to flow only in one direction. Such devices are also referred to as diodes, triodes, etc., depending on the number of electrodes present. Variable resistor (or rheostat) A device that variably resists an electrical current. The resistance can be changed by varying the contacts, allowing the resistor to slide around a length of wire. Voltmeter An instrument that measures electromotive force or potential difference between two points, usually in volts.     COPYRIGHT©2005 VICTORIA PACKING CORP. ALL RIGHTS RESERVED ( CTR-110505-ENG)