An electrical resistor with a relatively large temperature coefficient of resistance. Thermistors are useful for measuring temperature and gas flow or wind velocity. Often they are employed as bolometer elements to measure radio-frequency, microwave, and optical power. They also are used as electrical circuit components for temperature compensation, voltage regulation, circuit protection, time delay, and volume control. A common type of thermistor is a semiconducting ceramic composed of a mixture of several metal oxides. Metal electrodes or wires are attached to the ceramic material so that the thermistor resistance can be measured conveniently. The temperature coefficient of resistance is negative for these thermistors. Other types can have either negative or positive temperature coefficients.