Transcript IP2.23.4 Thermistors

IP2.23.4 Thermistors
Thermistors
© Oxford University Press 2011
IP2.23.4 Thermistors
 A thermistor is another special type of resistor. Its resistance changes as its
temperature changes.
 When the temperature of the thermistor is low, its resistance is high. This is
because a thermistor is made of a material which does not conduct
electricity well at low temperatures. The outer electrons are loosely bound to
the atoms and are not free to flow through the thermistor.
 As the temperature increases, more outer electrons gain enough energy to
break free from atoms. The electrons are then free to flow through the
thermistor.
© Oxford University Press 2011
IP2.23.4 Thermistors
© Oxford University Press 2011
IP2.23.4 Thermistors
© Oxford University Press 2011
IP2.23.4 Thermistors
 This graph shows the thermistor’s
resistance against temperature.
 Remember, the resistance of a thermistor
decreases as the temperature increases.
© Oxford University Press 2011
IP2.23.4 Thermistors
 This change in resistance according to their temperature
means that thermistors can be used as temperature sensors.
 For example, they can be used to warn drivers when the car
engine is overheating.
© Oxford University Press 2011
IP2.23.4 Thermistors
Most thermistors have a
useful working range of
–90 °C to 200 °C.
© Oxford University Press 2011