What you need

TH7 thermistor, smoothed power supply, heater and stirrer unit, interface, temperature, voltage and current sensors.

Setting up

Connect up the circuit as shown. Connect the current sensor to the first socket on the interface, the voltage sensor to the second socket and the temperature sensor to the third socket. If the sensors are adjustable, set a 1A range on the current sensor, a 5V range on the voltage sensor and a 0-100 range on the temperature sensor. Run your sensing software. You may need to do a short test run to establish a suitable voltage for the power supply. Your system may recognise the sensors automatically, otherwise you will need to set them up yourself. Set up the sensing software so that it will record for 20 minutes. Start recording as you heat water in a beaker until it is almost boiling. Allow it to cool as you continue recording.

Questions

What does the graph tell you about the change in temperature? What does the graph tell you about the change in current? What does the graph tell you about the change in potential difference? How does the temperature affect the current and potential difference?
Use the software to calculate the resistance (V / I). Get the software to plot resistance against temperature. Use the software to calculate Ln (Temperature). Use the software to calculate 1/Current. Plot this against Ln(temperature).

Teacher question

Is it easier to understand the relationships here by using sensors?