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A circle with a W and four terminals.
Also known as: Wattmeter, Power meter, Circle with a W
A wattmeter needs four terminals because it must measure current and voltage simultaneously and multiply them — two terminals cannot do that. In an AC circuit it reads real power, not the product of the ammeter and voltmeter readings, and the difference is the power factor.
Denotes a wattmeter: an instrument measuring electrical power by combining a current and a voltage measurement.
Contexts: Electrical equipment
Has four terminals — a current pair and a voltage pair — because power is a product of two quantities.
Contexts: Electrical equipment
Reads real power in an AC circuit, which is less than the product of RMS current and voltage by the power factor.
Contexts: Electrical equipment
A circle enclosing a capital letter W, with two leads on the current path and two on the voltage path.