In the First Law of Thermodynamics, heat supplied equals the increase in internal energy plus what?

The correct answer is work done. In the context of the First Law of Thermodynamics, which is often stated as the change in internal energy of a system being equal to the heat added to the system minus the work done by the system, it emphasizes the conservation of energy.

When heat is supplied to a system, part of that energy can be used to increase the internal energy of the system, while the remaining energy can be converted into work, which is the energy used to perform tasks such as moving a piston in a refrigeration cycle. Therefore, in this scenario, as heat enters the system, it can either increase the internal energy or be utilized to do work.

Understanding this relationship is crucial for applications in refrigeration and other thermodynamic systems, as it helps to clarify the balance of energy transfers in a closed system.