Which piece of electrical equipment does not require a magnetic field for its operation?

The operation of an electrostatic voltmeter relies on the principle of electrostatics rather than electromagnetism. This type of voltmeter uses the force that acts on charged plates to measure voltage without the need for a magnetic field. Unlike devices such as transformers, which operate based on magnetic coupling between coils, or solenoids, which rely on magnetic fields to create motion, the electrostatic voltmeter detects voltage by the electrostatic force between its charged elements. This distinction is critical in understanding the functionality of these various electrical devices, highlighting how some devices utilize electrical phenomena that do not involve magnetic fields at all.