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(General Physics) the principle that all gases expand equally for the same rise of temperature if they are held at constant pressure: also that the pressures of all gases increase equally for the same rise of temperature if they are held at constant volume. The law is now known to be only true for ideal gases. Also called: Gay-Lussac's law
[C18: named after Jacques A. C. Charles (1746–1823), French physicist who first formulated it]