Temperature, Volume and Pressure Relations

—In conformity with the laws of permanent gases, the mutual relations of the temperature, volume and pre ure of a gas in the cylinder of an engine vary according to the conditions which obtain at heating. 1. If the temperature of the gas is kept constant, an increase of volume results in a decrease of pre ure (Boyle’s Law). È 2. If the presure of the gas is kept constant, an increase of temperature results in an increase of volume. (Gay-Lu ac’s Law), 3. If the volume of the gas is kept constant, an increase of temperature résults in an increase of pre ure (Gay-Lu ac’s, Regnault’s, and Joule’s Laws). iv) A Under these conditions, a gas acts according to the following modes of expansion or compre ion: 1. For expansion, when the pre ure decreases as the volume increases, with a corresponding decrease in temperature due to the external work done by the gas in moving the piston. p 2. For compre ion, when the pre ure increases as the volume decreases, with an increase in the temperature due to the work spent upon the gas during the act of compre ion.