A thermisor is a heat sensitive device whose resistivity changes very rapidally with change of temperature. The temperature coefficient of resistivity of a thermistor is very high, which may be positive or negative. A thermistor can have a resistance in the range of `0.1 Omega` to `10^(7) Omega` Thermistors are used (i) to detect small temperature changes (ii) to safe guard the filament of picture tube of a television set against the variation of current (iii) in temperature contorl units of industry (iv) for voltage stabilisation and remote sensing.
