Thermistor

• The resistance of a thermistor changes with temperature because it's a semiconductor material, and as temperature increases, more electrons gain enough energy to move from the valence band to the conduction band, increasing the number of charge carriers and thus lowering the resistance. 
• Some of the most common uses of thermistors are in digital thermometers, in cars to measure oil and coolant temperatures, and in household appliances such as ovens and refrigerators.