Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

What happens to the resistance of an NTC thermistor as temperature increases?

1. It stabilizes at a fixed value

2. It sharply decreases

3. It gradually increases

4. It becomes infinite

The correct answer is: It sharply decreases

As temperature increases, the resistance of an NTC (Negative Temperature Coefficient) thermistor sharply decreases. NTC thermistors are designed to exhibit lower resistance at higher temperatures. This property is exploited in various applications, such as temperature sensing and circuit protection. In practical terms, as the temperature rises, the charge carriers within the thermistor gain energy, which enables them to move more freely and contribute to current flow. This increased movement results in reduced resistance. This characteristic makes NTC thermistors particularly useful for applications where accurate temperature readings and feedback are essential, as they can quickly respond to changes in temperature by altering their resistance accordingly.