The Law of Charles and Gay-Lussac (frequently called simply Charles' Law) is one of the gas laws, and relates the volume and temperature of an ideal gas held at a constant pressure. The law was first published by Joseph Louis Gay-Lussac in 1802, but he referenced unpublished work by Jacques Charles from around 1787. This reference has led to the law being attributed to Charles.
The law, expressed in symbols, is:
To maintain the constant during heating of a gas, at fixed pressure, requires that the volume increase. Conversely, cooling the gas decreases the volume. The exact value of the constant need not be known to make use of the law in comparison between two volumes of gas at equal pressure: