In the first law of thermodynamics, heat supplied equals the increase in internal energy plus what?

The first law of thermodynamics, often expressed as the principle of conservation of energy, states that the heat added to a system is equal to the change in internal energy of that system plus the work done by the system. In mathematical terms, this can be represented as:

Q = ΔU + W

where Q represents the heat supplied to the system, ΔU signifies the change in internal energy, and W indicates the work done by the system.

When heat is added to a system, it can either be stored as increased internal energy or used to perform work that results in energy being transferred out of the system, such as moving a piston in a refrigeration cycle. Therefore, the portion of heat that does not contribute to the increase in internal energy goes into doing work, making that the correct answer in this context. This understanding is crucial in various applications of thermodynamics, especially in refrigeration and heat transfer scenarios.