Wattmeter

The wattmeter measures electrical power, the product of the voltage across a load and the current through it, and shows the result in watts; as with a real wattmeter, its current terminals go in series with the load and its voltage terminals across it. Circuits in this tag compare the power taken by lamps and resistors in series and in parallel, check P = V × I against separate voltmeter and ammeter readings, and look at power in AC circuits with reactive parts. For example, "Watt's Law" measures a lamp's power and compares it with the multimeter readings.