What does a wattmeter measure in an electrical circuit?

A wattmeter is an instrument specifically designed to measure electrical power in an electrical circuit. It quantifies the rate at which energy is consumed or produced, which is expressed in watts. The wattmeter achieves this by measuring both the voltage across the circuit and the current flowing through it and subsequently calculating the power using the formula: Power (P) = Voltage (V) × Current (I).

This functionality is crucial for determining how much electrical energy is being used, which is important for evaluating energy efficiency, conducting load studies, and determining costs associated with electricity use. Other measurement instruments are designed for different electrical parameters: voltmeters measure voltage, ammeters measure current, and ohmmeters measure resistance, but only a wattmeter focuses on electrical power.