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Charles’ law of gases

Charles’ law of gases

Answer: In 1787 a French scientist, mathematician, inventor and balloonist J.Charles (Jacques Alexander Cesar Charles) studies the relationship among volume and temperature at costant pressure.  He described how gases tend to expand when heated.

Statement or Definition: According to this law “ the volume of a given mass of a gas is directly proportional to the absolute temperature if the pressure is kept constant.


When pressure is kept constant the volume of a given mass of a gas is directly proportional to absolute temperature on kelvin scale.

Mathematical Expression:


OR           V α  T

OR            V = KT

OR                V/T  = K

Where k is proportionality constant. If temperature of the gas is increased, its

volume also increases. When temperature is changed from T1 to T2 , the volume changes from V1 to V2 . The mathematical form of Charles’ Law in this case will be:

V1/T1 = K          AND             V2/T2 = K

As both equations have same value of constant, therefore , their variables are also equal to each other.

V1/T1 =V2/T2

Experimental Verification of Charles’s Law

Let us take a certain amount of gas enclosed in a cylinder having a movable piston. If the initial volume of the gas V1 is 50 cm3 and initial temperature T1is 25 °C, on heating the cylinder up to 100 °C, its new volume V2 is about 62.5 cm3. The increase in temperature, increases the volume.


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