The primary use of a voltmeter is to measure electrical potential difference, or voltage, across two points in an electrical circuit. This device helps individuals and technicians assess the electric potential, ensuring that devices operate within safe voltage limits. Voltmeters can be found in various forms, including analog and digital types, and they are essential tools in both educational settings and professional environments like engineering, maintenance, and troubleshooting. Accurate voltage measurements are vital for diagnosing electrical issues, ensuring proper function, and maintaining safety in electrical systems.