Millwright Level 1 Practice Exam 2025 - Free Millwright Practice Questions and Study Guide

The main function of a Ground Fault Circuit Interrupter (GFCI) is to detect ground faults, which occur when there is an unintended path between the electrical current and the ground. When a GFCI senses an imbalance between the current flowing into an electrical device and the current returning from it, typically due to leakage current, it quickly interrupts the circuit to prevent electrical shock, electrocution, or fire hazards.

This device is particularly important in areas where electrical equipment may come into contact with water, such as kitchens, bathrooms, and outdoor settings, thus providing an essential level of safety. By detecting the drop in current and switching the power off, a GFCI protects users from potentially dangerous situations.

In contrast, the other options relate to different functions that do not apply to a GFCI. Sensing overcurrent and switching power off is a function of circuit breakers, controlling the speed of a grinder pertains to variable speed drives or controllers, and providing electrical insulation is typically related to insulation materials rather than the function of a GFCI.