What is the primary distinction between watts and volt-amperes?

The primary distinction between watts and volt-amperes lies in their definitions and the types of power they represent in an electrical system. Watts are a unit of measurement that quantifies real power, which is the power consumed by electrical devices to perform work. This includes the energy converted into heat, light, motion, or other forms of useful work in a circuit.

In contrast, volt-amperes are a measure of apparent power in an electrical circuit, which combines both real power and reactive power. Apparent power is the product of the root mean square (RMS) voltage and current. While volt-amperes account for the total power in the circuit, not all of this power is used effectively for doing work, as reactive power can be present due to inductive or capacitive components in the system.

Thus, the answer correctly identifies that watts measure real power, which is critical for understanding the actual energy utilized in systems, versus volt-amperes which represent the total capacity of an electrical system regardless of the effective work being done.