NEIEP Machine Room Maintenance (550) Practice Test 2026 - Free Machine Room Maintenance Practice Questions and Study Guide

Capacitors store energy in an electric field and can keep a voltage across their terminals long after the power is removed. In industrial equipment, especially with large capacitors in power supplies or drives, this stored energy can remain for days if there isn’t a discharge path. The rate at which a capacitor loses its charge depends on leakage and any available discharge path; with a high capacitance and only a weak leakage resistance, the voltage can persist for a long time, which can be lethal. That’s why safety practices require treating capacitors as energized until you verify they are discharged with proper testing and use a suitable discharge method. The other choices don’t fit because a capacitor can indeed hold voltage after power off (not “Not at all”), and the danger isn’t limited to large capacitors—even smaller ones can be hazardous if charged to high voltage.