# Physics coursework

Physics coursework

Jaypal Sandhu 12c

## Mr.Rugg

How does different temperatures affect the resistance of a metal wire/thermistor.

Aim (preliminary):

The preliminary aim of my coursework was to measure what affect different temperatures have on the change in resistance of a copper wire.

Apparatus:

• Distilled water
• Heat proof mat
• Tri pod
• Bunsen burner
• Copper wire
• 5v power pack
• Electrical wires
• Crocodile clips
• Thermometer
• 100Ω resistor

Diagram:

In theory this was a good experiment however in practice it was not. Whilst conducting the experiment I realise that from the temperature changing from 0 degrees to 100 degrees there was only a small change of 0.01v. I tried with a different resistor but still had no luck. There was not enough change for me to conduct a worthwhile experiment. I tried to use a higher current on the power pack but still the voltage never changed of the copper wire and as a higher current was used I ad to press the reset button as the power pack continued to reset. Therefore I concluded that using copper wire to conduct this experiment was not appropriate as it’s resistively was too high to be affected by small or even large changes in temperature.

Instead of using a metal I decided to use a thermistor as it can be subjected to different temperatures and I can expect some results

Aim:
The aim of my investigation is to see whether the resistance of a thermistor (a type of temperature sensitive resistor) is directly proportional to the temperature.  I'm anticipating that this experiment will be interesting and relatively challenging because a thermistor is a type of resistors whose resistance changes significantly when its temperature changes, consequently a slight variation in temperature can lead to a vast change in the resistance, therefore I have to be extremely accurate when calculating the temperature as a mistake or inaccurate reading on the thermometer will affect my results considerably.

Introduction:
I have decided to use a thermistor in this investigation due to its stability, resolution/sensitivity, suitable range, consistency and low cost. As a medium in which to test the thermistor's behaviour, I have chosen distilled water - It is accessible and a high specific heat capacity. The specific heat capacity of the medium needs to be a lot larger than thermistor's so that the temperature of the medium remains constant when the thermistor is immersed in the water.

Thermistors are thermally sensitive resistors and have, according to type, a negative (NTC), or positive (PTC) temperature coefficient. They work because at low temperatures, electrons are fixed onto atoms and so cannot move. As the electrons get hotter they receive enough energy to break away from their atoms, so the thermistor becomes a better conductor.

In this experiment I do not know if I will have a NTC or a PTC thermistor but if the resistance decreases as the temperature increases then I will know I am using a NTC thermistor, if the temperature and resistance are opposite to that ...