How does a varistor function in an electrical circuit?

A varistor functions as a voltage-dependent resistor that helps protect electronic components from voltage spikes by conducting excess voltage to ground when it exceeds a certain threshold, known as the clamping voltage. This operation is crucial in safeguarding sensitive devices from transient voltage surges that could otherwise lead to failure or damage.

When the voltage across the varistor increases beyond its specified clamping rating, the varistor changes its resistance properties dramatically, becoming a low-resistance path. This allows it to divert the excess voltage away from the protected circuit components and send it safely to the ground. This action mitigates the risk of overvoltage damage, making varistors essential components in the design of surge protection systems for electrical and electronic devices.

In contrast, other options reflect different functionalities that do not align with the specific behavior of a varistor. For instance, acting as a continuous conductor does not accurately describe a varistor's role, as it only conducts when the voltage threshold is exceeded. Similarly, while current regulation and preventing short circuits are important functions in electrical systems, they are not roles that a varistor directly fulfills.