A wattmeter is an instrument used to measure electric power consumed i.e energy absorved in unit time by a circuit. The wattmeter consists of a movable coil arranged between a pairof fixed coils in the form of a solenoid. A pointer is attached to the movable coil. The free end of the pointer moves over a circular scale. When current flows through the coils, the deflection of the pointer is directly proportional to the power.