Method and Equipment:
I will need for this experiment wire (either Copper, Nichrome or Constantan), a ruler, a power box, circuit wires, an ammeter, a voltmeter, and crocodile clips.
First I will set up the circuit with the ammeter and voltmeter in it. The voltmeter must be in parallel with the circuit it is measuring, while the ammeter goes in series. I will leave to open connections in it with crocodile clips on to allow the circuit to connect to the different wire thicknesses. Then I will connect one of the wires to the two crocodile clips, then turn on the power (I will keep this at 6 Volts), then take the readings. I will have to do this quickly so that the wires don’t overheat and possibly melt themselves and anyone who touches them. Then I will double up the wire so that there are two lengths of the wire connected in the circuit, and then repeat the experiment. I will do this twice with each thickness of wire, and go up to 8 times the original thickness. Doing teach thickness twice will ensure a better set of results, because any anomalies will be shown up and then corrected by a better value.
Results:
Interpreting Results:
I will now find the gradients for each type of wire:
0.026/10=0.0026Ω per centimetre
0.037/20=0.00185Ω per centimetre
0.051/30=0.0017Ω per centimetre
0.068/40=0.0017Ω per centimetre
AVERAGE=0.0019625Ω per centimetre
FACTORY=0.00108Ω per centimetre
0.078/10=0.0078Ω per centimetre
0.125/20=0.00625Ω per centimetre
0.182/30=0.00607Ω per centimetre
0.233/40=0.005825Ω per centimetre
AVERAGE=0.00648625Ω per centimetre
FACTORY=0.0067Ω per centimetre
0.33/10=0.033Ω per centimetre
0.51/20=0.0255Ω per centimetre
0.94/30=0.0313Ω per centimetre
1.34/40=0.0335Ω per centimetre
AVERAGE=0.030825Ω per centimetre
FACTORY=0.0302Ω per centimetre
Conclusion:
From my results I can see that increasing thickness decreases the overall resistance of the circuit. This is because there is more room for the same number of electrons to travel through. This means that the circuit can pass through easier with less resistance from the copper wire. We can see this on the graph because the line of best fit shows a downward slope.
I should have done more experiments because this would have made it more viable, and may have cut down on anomalies such as the last result, which doesn’t fit into the pattern.
In addition to the initial experiment I also looked at how the length and the type of the wire affected resistance. I did both together so first I will look at the effects of length.
By looking at my results for each type of wire I can see that an increase in length of wire directly affects an increase in resistance. This is because the current has to pass through more of the resistant material to complete the circuit. We can see this from my graph of the three metals, because each of the three lines is an upward line. This shows that it is obviously a general rule that increased wire length directly increases the resistance.
Next is the type of wire used. From the tables and graphs we can see that the metal with least resistance is Copper, Constantan is in the middle, and Nichrome has the highest. This will be because of the chemical structures of each metal differs so that the number of free electrons differs in each metal – Copper will have most whilst Nichrome has the least.
From calculating the average gradients of each type of wire also, I can see the relationship of ohms per centimetre of wire. This too shows Copper to have the lowest resistance, and Constantan to have the highest. The factory rating below is the officially released ohms per centimetre rate. My experimental results were on average the same as these ratings, so they seem to be fairly accurate.
Evaluation:
To improve on my results I would have included more experiments in my experiment of thickness of wire. This is because it would have made it much more accurate. Seeing as I only did this experiment once, there could well have been some anomalous results which would have been avoided if I had redone the experiment a few more times. However, the results seemed fairly consistent with each other, as well as with my hypothesis.