What is an isothermal process?

An isothermal process is defined as a thermodynamic process that occurs at a constant temperature throughout the system. In such processes, the internal energy of an ideal gas remains constant, since internal energy is a function of temperature.

When a gas undergoes an isothermal expansion or compression, the heat added to or removed from the system exactly balances the work done on or by the gas, ensuring that the temperature remains unchanged. This principle is particularly relevant in thermodynamic cycles, such as in Carnot engines, where isothermal processes play a crucial role in achieving maximum efficiency.

In contrast, processes characterized by constant pressure or constant volume involve different thermodynamic relationships and behaviors, where temperature may change as a result. Similarly, a process occurring without heat transfer refers to an adiabatic process, which also does not maintain a constant temperature. Understanding isothermal processes helps engineers and scientists analyze and design systems involving gases under controlled temperature conditions.