A resistor used to detect temperature is known as a thermistor (short for "thermal resistor"). The resistance of a thermistor fluctuates considerably as the temperature changes, in contrast to normal resistors, whose resistance is intended to remain constant regardless of temperature. A thermistor can precisely convert differences in electrical impedance into variations in temperature once it has been measured.

The temperature of interior components is frequently monitored by thermometers in computers. Thermistors, for instance, can be used to monitor the temperature in close proximity to the Processor, Memory ports, and power source. The circuitry of the computer typically houses these thermistors. A sensor that is incorporated into the semiconductor usually measures the real temperature of parts like the CPU and memory sections.

Thermistors' data is used by computers to avoid burning. For instance, a processor's temperature may steadily rise if it is used at close to capacity for a prolonged length of time. When this occurs, the computer may accelerate its internal fans to boost ventilation and keep it fresh. In unusual situations, like when a laptop is used outside on a sweltering day, the fans might not be able to maintain a secure temperature for the computer. The computer may close down if the thermistors detect a perilously high temperature in order to prevent burning and system damage.