Kilopascal wrote in USMA 18519: >I believe the Watt is the SI unit of ALL power, not just mechanical power as >you state. I'm sure you didn't mean it as you wrote it, but others less >knowledgeable might think you are stating the watt is strict a unit of >mechanical power. > >John
>> Remember that the watt is the SI unit of >> mechanical power, and I believe it is used in Australia by the motor >> vehicle trade. The electric power required by the motor of an air >> conditioner is measured in watts. The mechanical output of the motor >> should also be in watts. The cooling power should also be in watts. (1 >> ton of refrigeration = 3514 W). I meant that literally. James Watt, after whom the watt is named, developed steam engines in the 18th century, nearly a century before electricity became important. The definition of the watt includes metre, kilogram and second, or specificly m2.kg.s-2, nothing purely electric about it. As I mentioned, the Australians use it to measure the power of their automobiles. But due the coherence of the metric system, the watt is also the unit of electric power, and the unit of thermal power. The electric units of current and electromotive force presented a problem. There were electrostatic units, electromagnetic units, and the "international" units which were introduced by the International Electrical Conference held in Chicago in 1893. Giuseppi Giorgi in 1901 solved the theoretical problem of fitting the international electric units into a coherent metric system by proposing that the ampere (or the volt) should be named as a base unit of the system, in addition to the metre, kilogram, and second. This was a change from the metre-kilogram-second system to the metre-kilogram-second-ampere system. This proposal was adopted in 1935 by the *Commission Electrotechnique Internationale*, and in 1950 the Commission adopted the ampere as the 4th base unit. All the other units could now be defined with only the numerical factor one in their definitions. Joseph B.Reid 17 Glebe Road West Toronto M5P 1C8 TEL. 416-486-6071
