Heat

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.

Units of Heat

C.G.S unit: 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
It is the amount of heat required to raise the temp, of 1 pound of pure water through 1°F. It is also called B.Th.U (British Thermal Unit).

Relations between different units :
1 B.Th.U = 252 calorie
1 calorie = 4.186 joule 1 pound calorie = 453.6 calorie
1 Therm = 10₅ B.Th.U.

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.

Scales of temperature measurement
To measure temperature two fixed points are taken on each thermometer. One of the fixed points is the freezing point of water or ice point as lower fixed point (LFP). The other fixed point is the boiling point of water or steam point as upper fixed print (UFP).

Range of different thermometers :
Mercury Thermometer : from -30°C to 350°C
Constant volume gas thermometer: from -200°C to 500°C
Platinum resistance thermometer : from - 200°C to 1200°C
Thermocouple thermometer: from - 200°C to 1600°C