What is Charles' law formula?
The physical law that the volume of a fixed mass of gas held at a constant pressure varies directly with the absolute temperature.
This law states that the volume of a given amount of gas ,at a constant pressure gas varies with its temperature
or simply we can say that the volume of gas changes with its temperature. At a higher temperature , a gas will take up more volume ( expands) , at a lower temperature, a gas will take up lesser volume or it contracts.
Let us suppose that we have a given amount of gas enclose in a balloon, the temperature of the gas is
as per the law the ratio of Volume / temperature stays the same, if one increases , the other decreases but the ratio does not change.
equating the two equations (a) and (b)