# How to solve a problem on Charles' Law?

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### 2 Answers

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`

Charles Law is:

`("V_1")/("T_1") = ("V_2")/("T_2")`

Volume and temperature are both proportional with each other. When volume increases, so does temperature. Likewise, when temperature increases, so does volume.

Your teacher will most liekly give you three out of the four values. With your given values, plug in accordingly and solve for your unknown,