What is the role of a varistor in a circuit?

A varistor is used to protect electronic circuits from voltage surges or spikes.

In electronic circuits, voltage surges or spikes can cause damage to components and even lead to complete failure of the circuit. A varistor, also known as a voltage-dependent resistor (VDR), is a component that is used to protect against these voltage surges.

A varistor is made up of a material that has a non-linear resistance characteristic. This means that its resistance changes with the voltage applied to it. At low voltages, the varistor has a high resistance, but as the voltage increases, the resistance decreases. When a voltage surge or spike occurs, the varistor's resistance drops significantly, allowing it to absorb the excess voltage and protect the rest of the circuit.

Varistors are commonly used in power supplies, surge protectors, and other electronic devices that are susceptible to voltage surges. They are also used in lightning arresters to protect buildings and other structures from lightning strikes.

In summary, the role of a varistor in a circuit is to protect against voltage surges or spikes that can cause damage to electronic components. By absorbing excess voltage, the varistor helps to ensure the safe and reliable operation of electronic devices.