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a unit of full power of an alternating current, designated by VA. The full power of an alternating current is defined as the product of the effective values of the current in a circuit (in amperes) and the voltage at its terminals (in volts). The effective values of the current and voltage are measured by AC ammeters and voltmeters . The concept of full power is distinct from the real power of an electric circuit, which is expressed in watts and equals UI cos φ where φ is the angle of displacement of the phases between voltage U and current I, and as distinct from the reactive power, equal to UI sin φ and expressed in vars.