THC to thermostatic

THC to Thermit (pressure) welding

THC. Tape Hiss Canceller. A pro­prietary single-ended noise reduc­tion system for cassette tape.
T -head engine. (Auto.) A cross-sec­tion of the motor block resembles the letter T. Valves are arranged on both sides of the engine, requiring two camshafts and two camshaft­drive gears. An expensive type of construction.
Theater effect Processing circuitry used to simulate the acoustic quali­ties of a music hall or theater.
Theorem. A truth capable of demon­stration. A proposition to be proved.
Theoretical. Pertaining to or depend­ing on an abstracfprinciple; specu­lative; ypothetical.
Theory. (Science) An attempt to account for the number of closely related observations or phenomena.
Therlo. (Metal.) An alloy of copper, aluminium, and magnanese, used for instrument shunts and coils. It has a low temperature coefficient; and its thermoelectric power against copper is very .low.
Thermal agitation. Continuos ran­dom movement of electrons ina con­ductor; increases with rising tem­perature.
Thermal conductivity. (Weld.) The ability of a metal to transmit heat through its mass. The rapidity with which a metal conducts heat should be taken into consideration both in preheating and in the size of the blowpipe selected.
Thermal energy. Energy that comes from heal.
Thermal jet engine. (Aero.) A jet engine thaI utilizes heat to expand gases for rearward ejection. This is the usual form of aircraft jet engine.
Thermal reaction. (Plast.) Heatgen­erated within the plastic by chemi­cal reaction during its solidifica­tion.
Thermal radiation. Radiation felt as heat.
Thermal runaway. Situation were heat generated in a component causes lowering of resistance, which permits greater currrent flow, causing more heat, etc., un­til circuit 'runs away'.
Thermal uniL (phys.) A unit cho­sen for the comparison or calcula­tion of quantities of heat; used as a standard for comparison of other quantities.
Thermionic. Applies to emission of electrons from a substance when heated. Cathode in vacuum web or valve is thermionic, hence thermionic valve.
Thermistor. Resistor having a high + or - temperature coefficient of resistance. Used for stabilising and protecting circuits.
Thermit. (ElIgill.) A mixture of powered aluminium, and a metallic oxide as iron, chromium, or mang-anese oxide. It is used extensively in welding by the thermit process.
Thermit (pressure) welding. A pres­ sure-welding process wherein theThermit welding to thermostatic heat is obtained from liquid prod­ucts of a thermit reaction.
Thermit welding. A nonpressure (fu­sion) welding process wherein the heat is obtained from liquid steel produced by a thermit reaction, and the filler metal is supplied by the steel produced in this reaction.
Thermo-couple. (Elec.) An electrical generator made by the welding to­gether, at one end, of two.dissjm.i.l~r metal rods or wires, which produce electricity at the free ends when the weld is heated; used in pyrometers for measuring extreme heat.
Thermo-dynamic. (Engin.) The science which treats of heat as a form of energy or mode of work.
Thermo-electric metals. Metals or alloys used in thermocouples for measuring high temperatures. Platinum, nickel, copper, rhodium etc., are much used.
Thermo-graph. (Aero.) An instrument for recording temperature. Thermometer. An instrument for measuring variations in temperature.
Thermo-nuclear reaction. (Chern.) A reaction in which two light nuclei combine to form a heavier atom, and thus releasing a large amount of energy.
Thermopile. (Elec.) A group of dis­similar materials arranged alter­nately in such a manner that the junctions can be heated to produce an electric current. .
Thenno-plastic. (Plast.) A plastic divi­sion in the families of plastics. (See Plastic~.) A resin product in these families can be repeatedly sof­tened by heat and changed in form. It hardens on cooling.
Thermoset. (Plasl.) A second plastic division. (See Plastics.) The resins in the families under ths category take a form in a mold where the~ are chemically changed by the reaction of heat and pressure which set the" 'material and reduces it to an infusible state.
Thermo-siphon system. (Auto.) This type of cooling system is based on the fact that hot water rises and cooler water settles in the system. Water heated by the engine rises within it and flows to the top of the radiator where it is cooled; by the time it reaches the bottom of the radiator it is relatively cool and starts on its round again. Thermostat. A device for automatic regulationof temperature.
Thermostatic. (Heaiing) In steam heating systems, device for drain­ing air and condensation from ra­diators, etc., without permitting the passage of steam. The discharge valve is operated by means of a diaphragm filled with a volatile liquid which causes the rapid ex­pansion or contraction.

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