Question

when we use Charles law ?

Answer 1

Charles' law (also known as the law of volumes) is an experimental gas law that describes how gases tend to expand when heated. A modern statement of Charles' law is:

When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be directly related.[1]

this directly proportional relationship can be written as:

or

where:

V is the volume of the gasT is the temperature of the gas (measured in Kelvin).k is a constant.

This law describes how a gas expands as the temperature increases; conversely, a decrease in temperature will lead to a decrease in volume. For comparing the same substance under two different sets of conditions, the law can be written as:

The equation shows that, as absolute temperature increases, the volume of the gas also increases in proportion.

Answer 2

Charles law states that for a given mass of gas , at constant pressure , the volume V] is directly proportional to the absolute temperature.i,e doubling the temperature will double the volume.It is an experimental gas law that describes how gases tend to  expand when they get heated.
                
                   Volume α Temperature

V is the volume of the gas
T is the temperature of the gas (measured in Kelvin).

Ideal gases is hypothetical. It  move rapidly and don't loose energy when they collide.There is  no inter molecular forces between the particles.