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© Javaid Khurshid, PIEAS Page 1 of 2
Experiment: STUDY THR VARIATION OF RESISTANCE OF A THERMISTER” WITH TEMPERATURE
Object: To study the effect of temperature (max. of 100 °C) on a thermistor (negative
• A given thermistor (negative temperature, coefficient)
• Power supply, 5 V, DC
• Mercury thermometer (-10C to +110 C)
• Beaker (250 ml)
• Heating arrangement
Formula: No formula is used Procedure:
i) Clean all the terminals of wires with sandpaper. ii) Make connections as shown in the figure iii) Dip only the thermistor in a beaker containing normal cold water having
thermometer in it. iv) Supply power to the circuit v) Take readings of temperature and resistance. vi) Place a heating source below the beaker. vii) Now slowly heat the water and note down the current in it corresponding
to changing temperatures ‘T’ (say 10, 20, 30… °C) in regular steps. viii) Finally, measure the resistance of the thermistor at 100°C when water
gets boiled. ix) Plot a graph by placing temperature “T” (°C) on X-axis and Resistance“R”
(ohms) on Y-axis.
© Javaid Khurshid, PIEAS Page 2 of 2
Observations: Take approximately 30 readings of different temperatures.
No. of obser- vation
Thermistor temperature T
Resistance R (ohms)
Result: Resistance of a thermistor decreases/increase with the increase in temperature.
• Connection must be tight.
• The points of contact of terminals should not add any insulting part of wires.
• The initial temperature and final temperature of thermistor must be measured accurately.
• The connecting wire of thermistor must be long enough in order to enable the thermistor to dip thoroughly in the water.
• The heating arrangement must be kept at a suitable distance away from the rest of the circuit.
• Heating must be done slowly.
Some Questions? • If the data is plotted on excel and interpolated, What will be the trend (linear, logarithmic,
polynomial, power, or exponential) for the highest R 2 value?
• If a thermistor is placed in an electrical circuit with constant DC voltage applied, what would be the effect of current through the circuit if the thermistor was heated up?
• What do you say about the material of a thermistor (Is it ohmic) ?
• When the thermistor is more sensistive to temperature variation?