I am going to investigate how the temperature of the wire affects its resistance.
Prediction:
I think that as I increase the temperature, the resistance of the wire will increase.
Background knowledge:
The resistance of the wire will increase when I heat it because as the atoms of the wire heat up they will gain more energy. As the atoms gain more energy, they will vibrate more and restrict the movement of the current particles by getting in their way and physically stopping them.
If I were to make the wire colder then the atoms will lose energy and slow down. This will allow the currents particles to pass through easier because less atomic activity will get in their way.
If I heat the wire the resistance will increase and if I cool the wire then the resistance will decrease.
Current flowing through wire at room Current flowing through heated wire.
temperature.
Apparatus list:
Power pack
Ammeter
Voltmeter
Copper wire (26cm)
Crocodile clips (2)
Water (500ml)
500ml Beaker
Thermometer
Tripod
Gorge
Bunsen burner
Connecting wire
Goggles
Safety mat
Method:
- Take the power pack, 26cms of copper wire, the ammeter and voltmeter, some connecting wire, two crocodile clips and the variable resister.
- Set up the apparatus to make a circuit as shown below.
Heat
- Then take the bunsen burner, the safety mat, the beaker of water (500ml), the safety goggles and the thermometer.
- Set the new apparatus up into the circuit as shown in the diagram.
Heat
- Place the copper wire in the water. Heat the water to 30°C and set the power pack 4 volts D.C.
- Turn the power on and record the voltage and current.
- Then heat the water to 40°C and record the voltage and current again.
- Increase the water temperature in stages by 10°C up to 100°C.
- Put the results into a table.
- When you have all the results, calculate the resistance by dividing the voltage by the current.
- Then put the results into a graph showing the temperature and resistance.
Fair test and accuracy:
I will make the test as fair as I can by keeping the current, the amount of water and the length of wire the same, but I will change the temperature of the water.
Safety:
I will make the test safe by wearing safety goggles, having a safety mat for the bunsen burner, not letting the water boil out of control and standing up so if the water spills then I can get away from it quickly.
Conclusion:
The graph tells me that as the temperature increases, the resistance of the wire also increases. This is because as the temperature increases the atoms in the wire start to move/vibrate more stopping the electric particles from passing so easily. The results and the prediction were similar although in my prediction I thought it would need less heat to create more resistant.
Evaluation:
The results show no unusual or unexpected findings in the course of the graph. The resistance increased as the temperature of the wire increased but more slowly than I had predicted. However, the experiment proved that the hotter the wire the greater the resistance. I do not therefore think that the experiment needs to be changed in any way.
The experiment could be altered to combine a test using a longer wire. If the length of the wire was increased from say 26cms to 52cms, I would expect the results to show that resistance increased at a faster rate. This would be as a result of increased resistance due to the increase in the length of the wire. I would use the same method although I would probably need to wrap the wire around a piece of wood as the wire would not fit into the beaker without touching itself thus creating a shorter circuit.
