A wattmeter measures what type of power?

A wattmeter measures true power, which is the actual power consumed by electrical devices when they operate. True power is quantified in watts (W) and is the portion of power that performs useful work in the circuit, such as lighting a bulb or running a motor. It takes into account the power factor of the circuit, which reflects how much of the electrical energy is being converted to useful work versus being wasted in the form of reactive power.

In the context of electrical systems, true power is fundamental because it represents the energy that is actually converted into work. This is distinct from other types of power like reactive power, which represents energy that oscillates back and forth in the system and does not contribute to productive work, and apparent power, which is the product of the total voltage and current in the circuit without factoring in the phase difference between them.

Thus, recognizing that a wattmeter is specifically designed to measure true power underlines its critical role in evaluating the performance and efficiency of electrical systems.