Gas Fitter Practice Test

The resistance of a thermistor ... as its temperature rises:

1. Increases

2. Decreases

3. Remains the same

4. Fluctuates

The correct answer is: Decreases

A thermistor is a type of temperature sensor whose resistance varies significantly with temperature changes. Specifically, a negative temperature coefficient (NTC) thermistor decreases in resistance as the temperature rises. This characteristic makes thermistors useful for temperature measurement and control because it allows them to provide a measurable electrical signal that correlates directly with temperature changes. When the temperature increases, the thermal energy allows more charge carriers to become available, thus reducing the resistance. This relationship is critical in applications such as thermostats and temperature-sensitive circuits where accurate temperature readings are essential. The ability to measure temperature through changes in resistance makes the thermistor a practical and efficient component in gas fitting systems, where monitoring temperature can be vital for safety and efficiency. In contrast, a positive temperature coefficient (PTC) thermistor would behave differently, as its resistance would increase with temperature. However, in the context of the question, the common type utilized in temperature sensing applications is the NTC thermistor, which confirms that the resistance decreases with rising temperature.