Heat

Heat is that form of energy which flows from one body to other body due to difference is temperature between the bodies. The amount of heat contained in a body depends upon the mass of the body.

If W work is performed and heat produced is H then W/H = or, W= JH

Where J is a constant called Mechanical Equivalent of Heat. Its value is 4.186 joule/ Calorie. It means if 4.186 joule of work is performed, 1 calorie of heat is consumed.

Units of Heat

C.G.S Unite: calorie = it is the amount of heat required to raise the temperature of 1 g of pure water through 1˚C.

International calorie: it is the amount of heat required to raise the temperature of 1 g of pure water from 14.5˚C to 15.5˚C.

F.P.S. unit: B. Th.U (British thermal unit) = it is the amount of head required to raise the temp. Of 1 pound of pure water through 1˚F.

Relations between different units:

1 B.Th.U = 252 calorie               1 calorie   = 4.186 joule

1 Therm = 10⁵ B.Th.U.               1 pound calorie = 453.6 calorie.

Temperature: Temperature is that physical cause which decides the direction of flow of heat from one body to other body. Heat energy always flows from body at higher temperature to body at lower temperature.

Measurement of Temperature

Thermometer: The device which measures the temperature of a body is called thermometer.