Ministerio del Poder Popular para la Educación Universitaria
Universidad Nacional Experimental “Rafael María Baralt”
Sede- Los Puertos de AltagraciaCátedra: Inglés II
Prof.: Marlon Céspedes
Jimenez, Adriana C.I.: 20.058.250
Beuses, Krisbell C.I.: 20.582.982
Peña, Lilissette C.I.: 20.583.336
Febrero de 2011
The operation of the common types of thermostats depends on a well-known physical principle, namely, that matter increases in volume with a rise in temperature and contracts when thetemperature drops. This principle is seen at work in the ordinary thermometer. With a rise in temperature the volume of liquid in the bulb increases and it is forced to a higher level in the stem. Asthe temperature drops the liquid contracts and goes to a lower level. The thermometer scale, instead of registering the volume of the liquid, indicates the corresponding temperature.
Applyingthis principle to the thermostat, the mechanical energy and resulting motion produced by changes in temperature are utilized to operate a gas valve or an electric switch. When the set temperature isreached, the expanding medium or temperature sensing element has moved enough to close the gas valve. When the temperature drops below the setting of the thermostat, the valve opens. Thus the gas valveis made to respond automatically and a uniform temperature is maintained.
The common gas thermostat operates on the principle described above, but the application of the principle varieswith different types. Thermostats used with domestic and commercial appliances may be classified as follows: rod and tube or solid rob type and the hydraulic type.
1. Rod and tube or solid rod type.Sometimes referred to as a rigid couple thermostat, this type depends for its operation on the expansion and contraction of a metal tube, inside of which is a rod communicating with a gas valve....