2026 Auxiliary Officer & Electrical Wizardry Challenge – Power Through the Core!

An isothermal process is defined by a constant temperature throughout the change. Because the temperature doesn’t change, the internal energy of an ideal gas stays the same, so any heat added goes into doing work (Q = W) rather than changing U. The option that states no temperature change directly expresses this defining feature, making it the best description of an isothermal process. The other qualifiers—constant volume or constant pressure—are additional conditions that can occur during an isothermal process but are not what defines it.