What happens to the pointer of a wattmeter when the current direction is reversed?

When the current direction is reversed, the behavior of the wattmeter pointer can vary based on the design of the instrument, but in many cases, the pointer continues to read up scale if it is designed to provide a reading in accordance with the magnitude of power flowing through the circuit regardless of the direction of current flow.

In typical wattmeter designs, the reading reflects the real power in the circuit which can remain positive even when current direction is reversed, assuming the load remains constant. Thus, the wattmeter measures the instantaneous product of voltage and current. Since the wattmeter is designed to measure power in both directions, reversing the current does not result in a zero reading; instead, the pointer simply continues to indicate the power being consumed or delivered in the system, but in the positive up scale direction.

This characteristic is important for applications where power measurements are necessary regardless of the current's direction, such as in alternating current (AC) systems, where the current and voltage continuously change direction.