Intro to Millwright Practice Exam 2025 - Free Millwright Skills Practice Questions and Study Guide

The device that measures the difference between incoming and outgoing electric current is a Ground Fault Circuit Interrupter (GFCI). This specialized electrical device is designed to protect people from electric shock by monitoring the current flowing through the circuit. It continuously compares the current entering and leaving the electrical circuit it protects. If it detects any imbalance—indicating that some of the current is leaking, possibly through a person to the ground—it will quickly shut off the power, thus preventing electrical shock.

This monitoring is crucial in areas where water is present, as the risk of electric shock is higher. The GFCI's ability to detect current differences enables it to respond quickly and safeguard users from potential hazards. In contrast, devices like transformers, multimeters, and circuit breakers serve different functions that do not specifically involve measuring the difference between incoming and outgoing current for the purpose of personal protection in the way a GFCI does.