Preliminary results
My preliminary results are good, but could be improved. In my real experiment I will increase the amount of times I try each length, and keep the voltage at 4V. In my proper experiment I will try to make a fair test by only changing one factor; the length of the wire. I will use the same type of wire to ensure that it contains the same atomic structure and the diameter will also be the same.
Equipment
- Power pack
- Length of nychrome wire
- Crocodile clips
- Ammeter and voltmeter
- Wire cutters
- Wires (for power pack etc)
Method
- Firstly, I set up the apparatus as shown in the circuit diagram making sure all wires were working and the power pack was set to 4V
- I then measured an 100cm long piece of nychrome wire and placed it between 2 crocodile clips
- I turn the voltmeter and ammeter on and finally the power pack.
- I took the readings and recorded them (see next page)
- I rearranged the crocodile clips to form lengths of wire 90cm, 80cm etc long and repeated the experiment for each length making sure the wire was accurately measured.
Results
Averages
Conclusion
All my results were satisfactory and I found no reason to repeat any lengths as there were no anomalous results.
After looking at my results in graph form with a line of best fit, I have found that my prediction was correct, with the resistance getting higher as the wire lengthened. It clearly shows this happening.
In my prediction I also mentioned that the shortest wire would have the least resistance and by looking at the tables you can see this is also very true.
The shorter wire however created the most heat, glowing bright orange at one point, I was expecting this as the current must flow very fast through a small and the friction causes the wire to heat.
Evaluation
If I were to do this experiment again there are a few things I would change to stop any problems occurring.
My experiment went very well and I found very few anomalous results on the length of 80cm – however this was only slightly inaccurate.
I would make sure that all measurements were exactly correct and that the power pack was on the correct voltage.
Next time I could also try a different type of wire, copper for instance, but would have to make sure that the connecting wires (which are also copper) were as short as possible to make sure there was no major resistance through them. This would provide me with more accurate results and a more reliable experiment.
I would also record my results in two or three decimal places to make sure that if, when rounded up and two or more numbers were the same, I would keep more decimal places and would therefore have a more accurate resistivity result.
I could also increase the number of different lengths, which would then create more results giving me a more accurate graph and line of best fit.
I would also allow myself more time so I can do the experiment more times and therefore have more results, so I could end up with a more accurate line of best fit.
The crocodile clips I would use would be sturdier as they clipped onto the wires very loosely, making them dangerous and prone to falling off.
Although using the same length of wire ensures a fair test, it could be damaged from previous circuits and lengths.
