# Difference between Varistors and Thermistors

**URL:** <https://forumautomation.com/t/difference-between-varistors-and-thermistors/14504>\
**Category:** Electronics\
**Tags:** electronics\
**Created:** [October 15, 2026, 3:35pm UTC](https://forumautomation.com/t/difference-between-varistors-and-thermistors/14504 "2026-10-15T15:35:34Z")\
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**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [October 15, 2026, 3:35pm UTC](https://forumautomation.com/t/difference-between-varistors-and-thermistors/14504/1 "2026-10-15T15:35:35Z")

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## Difference between Varistors and Thermistors

Thermistors and varistors are important components used in **[electronic](https://forumelectrical.com/basic-electronics-fundamentals-ac-to-dc-conversion/)** circuits, but they respond to different electrical conditions. Understanding their characteristics helps in selecting the right component for circuit protection.

## Thermistor (NTC)

An NTC thermistor decreases its resistance as its temperature rises. It is commonly used to limit inrush current when a circuit is powered on. Under normal operating conditions, it has relatively low resistance and allows current to flow.

## Varistor (MOV)

A metal oxide varistor (MOV) is designed to protect circuits against voltage surges. Under normal voltage conditions, it has very high resistance and draws very little current. When a voltage surge exceeds its conduction threshold, its resistance drops sharply, allowing it to divert surge current and help protect sensitive components.

 ![1](https://cdn.forumautomation.com/original/2X/1/16b1ee0909590560fedd4b4c2f774eb75ae58372.jpeg)

## Varistors vs. Thermistors

| **Feature** | **Thermistor (NTC)** | **Varistor (MOV)** |
| --- | --- | --- |
| Full Name | Negative Temperature Coefficient Thermistor | Metal Oxide Varistor |
| Operating Principle | Responds to temperature changes | Responds to voltage changes |
| Resistance Behavior | Resistance decreases as temperature increases | Resistance decreases sharply when voltage exceeds its threshold |
| Normal Condition | Relatively low resistance during normal operation | Very high resistance under normal voltage |
| Main Function | Limits inrush current during startup | Protects circuits against voltage surges |
| Typical Application | Power supplies, motor circuits, and electronic equipment | Surge protection in power supplies, control panels, and electronic devices |
| Protection Type | Inrush current limiting | Overvoltage and transient surge protection |

An NTC thermistor responds primarily to temperature, whereas a varistor responds primarily to voltage. They are not interchangeable because each performs a different function in circuit protection.