Joule's Second Law

Joule’s second law, also called the law of heating in a conductor, states that the internal energy of a gas is independent of its volume and depends only on its temperature.  In other words, for an ideal gas, the heat capacity at constant volume remains the same regardless of the gas’s pressure or volume, meaning that any change in the internal energy of the gas is directly related to a change in its temperature.  This law implies that the energy associated with the random motion of molecules in an ideal gas is unaffected by how much space the gas occupies.  Joule’s second law is significant because it provides the foundation for understanding the thermodynamic behavior of ideal gases and supports the idea that internal energy is purely a function of temperature in such systems.