Wattmeter

—An electrical instrument designed to measure directly the products of the amperes and volts in a circuit and give its readings in watts, a volt-ammeter. In the dynamometer type there are two coils, or sets of coils, one of which is fixed and the other movable. The movable coil is connected in the current circuit, and the fixed coil in the pre ure circuit, or the reverse. The induction type is used on alternating current circuits. In this type, electromagnets are arranged near a vane in which eddy currents are caused to flow which react on the magnetic field, and the record made is proportional to the force of the reaction. A recording wattmeter is one that will register the watt-hours expended during an interval of time.