Core Practical 12: Calibrating a Thermistor (Edexcel A Level Physics)

Revision Note

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Lindsay Gilmour



Core Practical 12: Calibrating a Thermistor

Aim of the Experiment

  • To calibrate a thermistor so it can be used as a thermometer


  • Independent variable = temperature (oC)
  • Dependent variable = resistance of thermistor (Ω)
  • Control variables:
    • Temperature gradient controlled by stirring


  • Power source
  • Thermistor
  • Fixed resistor
  • Ohm-meter
  • Bunsen burner, tripod and gauze
  • Beaker filled with crushed ice
  • Stirring rod
  • Liquid in glass or mercury thermometer with range -10 - 100oC

  • Resolution of measuring equipment:
    • Thermometer = 1oC
    • Ohm-meter = 0.01 Ω




  • Set up the equipment with the thermistor immersed in the ice, the ohm-meter connected to record the resistance of the thermistor by placing it in parallel across it, and the fixed resistor in series with the thermistor
  • Place the beaker of ice onto the tripod, without lighting the Bunsen burner
  • Measure and record the temperature and reading on the ohm-meter
  • Light the Bunsen burner and keep to a gentle flame
  • Stir the ice / water gently at all times to keep the temperature as even as possible throughout the beaker
  • At approximately 5oC intervals record the new temperature and resistance reading
  • Continue until the water is boiling


  • Plot a graph of resistance against temperature
  • Use the temperature graph to find the resistance at a given temperature

Evaluating the Experiment

Systematic Errors:

  • Read the thermometer at eye level
  • Check the zero error on the ohm-meter by connecting the leads across the terminals

Random Errors:

  • Allow time for the temperature to reach equilibrium
  • Stir the water before readings
  • Ensure thermometer bulb is completely submerged in the water and level with the thermistor
  • Turn off current between readings to avoid heating in the wires

Safety Considerations

  • Risk of instability, use a stand and clamp to support leads
  • Hot equipment and boiling water must be handled with care and allowed to cool down where possible
  • Keep plastic cables / leads away from hot metal
  • Check the voltage limit of the thermistor and stay within guidelines

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Lindsay Gilmour

Author: Lindsay Gilmour

Lindsay graduated with First Class Honours from the University of Greenwich and earned her Science Communication MSc at Imperial College London. Now with many years’ experience as a Head of Physics and Examiner for A Level and IGCSE Physics (and Biology!), her love of communicating, educating and Physics has brought her to Save My Exams where she hopes to help as many students as possible on their next steps.