I decided on using this equipment because I have used these before in previous experiments and they proved to be most very reliable and trustworthy.
I will set up the equipment as follows:
The blue wire in the centre will be the variable area. The various different wires that are being tested go here, the rest of the circuit stays constant at all times to ensure a fair test (save the rheostat – the reason for this will be explained in the method).
The wire I am going to test is Nichrome wire. This proved to be most reliable for getting a good spread of results in my previous experiments. I’ve tried copper, and the results are shown below:
As you can see, these results are not very reliable as there is little spread to go off. The resistance is more or less the same every time. This is because copper wire has a very little resistance, which is why copper is the most commonly used material to make wires out of.
I also discovered while testing the copper wire that I will need a larger amount of results, as 5 will not be enough to use.
I have decided to test 10 different lengths of wire (ranging from 10 centimetres to 1 meter) and also three different thickness of wire (28, 32 and 34 SWG). This should give me adequate results to analyse.
The reason I am setting the power pack to a low voltage of 4 and using a rheostat is because of knowledge that temperature also affects the resistance in a circuit. I don’t want the wire to become too hot, or it will start affecting my results. Also, it is safer to me that the wire does not heat up too much and burn my hands.
I predict that the longer the wire is the more resistance there will be, and also the thicker the wire the less resistance. This is because resistance is caused by the electron’s collisions as they flow through the circuit. With a longer wire the collisions will be more frequent, as there will be more particles with which the electrons could potentially collide with. With a thicker wire the collisions will be less frequent, as there will be more room for the electrons to move about and not collide with other particles. The reason temperature will affect my results is because the higher the temperature the more energy the particles and electrons in the circuit will have and move much faster and collide more often with a bigger force. This is also why increasing the voltage in a circuit would increase the resistance, as you would be giving the electrons more energy.
Method
When the equipment is set up as is in the diagram I provided then I would be ready to start my experiment. Making sure the rheostat is set to maximum power I will then cut the 28SWG Nichrome wire to 1 meter and connect it to the circuit (in the blue area). I will then record the values given by the ammeter and voltmeter, before setting the rheostat to medium power and recording the results again and then finally setting it to minimum power and record the results once again. Then the average current will need to be formulated using these results, as will the average voltage. Then, when these two are known the resistance can be worked out by using the formula: R = V / I
When all this is done I will cut 10cm off the wire (which makes it 0.9m) and do this all again. When I have recorded the results for a 10cm piece of wire I will then be moving onto 32SWG wire and finally 34SWG wire.
This will provide me with many results to analyse and work out if it agrees with what I said in my prediction above.
Results
Nichrome 28SWG
Results
Nichrome 32SWG
Results
Nichrome 34SWG
Analysis of results
Now that I have collected my results I can start my analysis of them.
I have noticed that there is indeed a pattern in my results, and this pattern does agree with that I have said in my prediction.
It seems that the shorter the length of the wire is then the more less resistance is in the circuit, and that the thinner the wire is the more resistance in the circuit.
Conclusion
I am very confident that these results are trustworthy. Indeed it does show on the 28 and 32 SWG graphs that there are some anomalous results, but there is still a clear pattern that:
The thicker the wire is the less resistance is in the circuit. This is because the electrons and particles have more space in the circuit to move. If the wire was thinner then the particles would have less room and this would cause more collisions with other particles, thus the resistance will be higher.
The longer the wire is the more resistance is in the circuit. This is because there are more particles for the electrons to collide with if the wire is longer and so this will increase the resistance.
Evaluation
If I had performed this test again I would definitely strive for more accuracy with my results. Although a clear pattern still emerged from them I feel that they were not up to my standard.
On this experiment I was manually setting the rheostat’s power by hand, so this was bound to create some minor errors. If I could get hold of some equipment that would let me input values into a rheostat to make sure that it is set to the same power every time, then I would definitely use it, as it is likely then that the accuracy of my results would improve.