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Temperature

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-237

2025-11-20

412

The terms "hot " and "cold" are purely relative. Whether one body is hotter or colder than another depends upon whether it can itself impart heat to the second body, or receive heat from it. The condition of a body in this respect is called its temperature, and depends directly upon its molecular kinetic energy. If m is the mass of one of the molecules of a body, and v its average velocity at a certain temperature, the expression for its molecular kinetic energy  is 1/2 mv². Hence the temperature of a body is directly proportional to the square of the average velocity of its molecules.

If one body is put into contact with another, the one that has the higher temperature will lose some of its heat, and the one that has the lower temperature will gain heat, until they both finally come to the same temperature.

Temperature must not be mistaken for quantity of heat. A cup of hot water taken from a pailful will have the same temperature, but will contain very little heat in comparison with the water in the pail.