Current-Voltage Graph for Thermistors and LDRs

Thermistors are made of semiconductor materials.Initially there are few charge carriers per unit volume (conduction electrons).When the temperature increases the electrons that are bound to the atom gains energy and break free so there are more conduction electrons.As a result there are more charge carriers per unit volume so the resistance decreases. The resistance of light dependent resistors depends on the intensity of the light incident on them. In conditions of high light intensity the LDR has a lower resistance.LDRs are made from semiconductor material. Light energy can promote electrons from the valence band to the conduction band so there are more charge carriers per unit volume.