# How to solve a problem on Charles' Law?

Charles law is the law that an ideal gas obeys when it is subjected to a transformation under constant pressure. It is a relation that relates the volume of a gas `V`  to its absolute temperature `T` which can be written in its simplest form as

`V/T =constant`

To solve...

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Charles law is the law that an ideal gas obeys when it is subjected to a transformation under constant pressure. It is a relation that relates the volume of a gas `V`  to its absolute temperature `T` which can be written in its simplest form as

`V/T =constant`

To solve problems using the Charles law first one defines the values he knows, like for example initial and final volumes of the gas `V_i` and `V_f` and initial temperature `T_i` . Then one writes the Charles law in the form

`V_i/T_i =V_f/T_f`

and from this relation one finds the value of the unknown variable (final temperature in this example)

`T_f = V_f/V_i*T_i`

Remember, in Charles law the volumes `V_i` and `V_f` are expressed in `m^3` and the temperatures `T_i` and `T_f` are expressed in Kelvin degrees (they are absolute temperatures). The relation between the absolute temperature (denoted usually by  `T` ), and the Celsius temperature (denoted usually by `t` ) is

`T = t +273.15`

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