What is the purpose of a metal-oxide varistor (MOV)?

The purpose of a metal-oxide varistor (MOV) is to protect against voltage spikes. MOVs are widely used in electrical circuits as protective devices that can absorb and redirect excess voltage that may occur during surges, such as those caused by lightning strikes or power fluctuations. When the voltage across an MOV exceeds its specified threshold, it becomes conductive, allowing the excess voltage to flow through it rather than through sensitive components in the circuit. This action helps to prevent damage to equipment by clamping the voltage to a safer level.

In contrast, the other options do not accurately describe the function of an MOV. For example, the ability to store electrical energy is primarily associated with capacitors, not MOVs. Measuring electrical current is a task performed by current sensors or ammeters, while providing grounding in circuits is handled by grounding conductors and related components. Therefore, the designation of the MOV as a protective element against voltage spikes is what makes the chosen answer correct.