Thermistors are temperature-sensitive resistor. Their ability to conduct voltage is affected by the temperature. A dryer’s circuit board is programmed to respond to the level of voltage conducted by the thermistor.
The principal benefit of thermsitors compered to other types of temperature-sensitive resistors, is their sensitivity. Thermistors react to even mild changes in temperature. They can accurately detect wave of less than a single degree in temperature.
Overheating could destroy the whole appliance, but because the thermistors are high sensitive devices, they can helps prevent dryers from overheating.
The sensitivity of thermistors also carries some shortcoming. Thermistors can be damaged or destroyed if temperature undulate outside of the acceptable range. If the thermistors is broken, the dryer will not operating at all. All of the thermistor are custom-made, they are rarely interchangeable. So it can be hard to find replacements for old, out-of-date appliance.