GCSE Design Technology Practice Exam 2025 – Your All-in-One Guide to Exam Success!

A thermistor is a type of temperature sensor that changes its electrical resistance in response to temperature variations. In this case, when the temperature decreases, the resistance of a thermistor increases. This characteristic is what makes thermistors particularly useful in temperature sensing applications.

Thermistors typically come in two types: NTC (Negative Temperature Coefficient) thermistors and PTC (Positive Temperature Coefficient) thermistors. The NTC type, which is the more common variant in many applications, demonstrates the behavior described in this answer. As the temperature decreases, the molecular motion within the material slows down, leading to an increase in resistance. Conversely, for a PTC thermistor, the resistance would increase with an increase in temperature, but this does not apply to this question's context where we are discussing the behavior in response to temperature reduction.

This inverse relationship between temperature and resistance is what enables thermistors to be effective in temperature measurement and control systems. Their sensitivity allows for precise monitoring, which is crucial in various applications like climate control systems, automotive temperature regulation, and medical devices.