# Charles's law

Charles's Law is a basic law in physics and chemistry. It describes the relationship between the temperature and volume of a gas, if the pressure and amount of gas do not change. It is also known as the Law of Charles and Gay-Lussac or the Law of Volumes.

According to Charles's Law, the volume of a gas is directly proportional to its temperature when measured at a constant pressure. In other words, as the temperature of a gas increases, its volume increases, and as the temperature decreases, its volume decreases. This relationship can be written mathematically as:

V₁ / T₁ = V₂ / T₂

where V₁ and T₁ are the initial volume and temperature, and V₂ and T₂ are the final volume and temperature.

Charles's Law assumes that the pressure and amount of gas do not change. In reality, pressure can influence the behavior of gases, so the ideal gas law, which uses all three variables (pressure, volume, and temperature), often describes gas behavior more accurately.

Charles's Law is particularly useful in applications involving the expansion or contraction of gases due to temperature changes, such as in gas thermometers or the behavior of gases in various engineering processes.