4.3. Operating principle Some examples include sliding-contact devices and potentiometers, in which/ changes; resistance strain-gages, in Which L and p change : and thermistors, photoconductive light detectors, piezoresistive strain gages and resistance temperature detectors, in Which p changes4.3.1 Operating principle Some examples include sliding-contact devices and potentiometers, in which L changes; resistance strain-gages, in which L , A , and  change; and thermistors, photoconductive light detectors, piezoresistive strain gages, and resistance temperature detectors, in which  changes