Preliminary Work
In order to find the optimum conditions to undertake the experiment I did a preliminary experiment and tried it out with varying lengths and materials until I found the optimum set up. I took two different wires, one with a 22 SWG (Standard Wire Gauge) and one with 24 SWG. I then passed a current of 20 Volts through it and took a reading using a digital ammeter and digital voltmeter. My Results were:-
So, you have done this preliminary experiment. What exactly was its purpose? What decisions have you made about the design of your experiment as a result of this work?
Diagram of the Set Up for the Experiment
Method
First of all I shall set up the experiment as shown in the diagram, using a digital voltmeter and a digital ammeter, to more enable accurate readings than if I used an analogue one. I shall then get six lengths of constantan wire, each with different SWG (Standard Wire Gauge) ratings (22, 24, 26, 28, 30 and 32) and a length of 60 cm. I shall then attach one length of wire to the circuit using crocodile clips and pass a current of around 2 Volts through it. I shall then take down the Voltage and Amperes and repeat the experiment with a different wire. Once I have done this with all the wires I shall repeat the experiment another two times to enable me to make the results more accurate.
Skill O
Obtaining Evidence
Results
Changes to Method
I did not make any changes to the method while I was carrying out the experiment as I felt that everything worked fine and continued to do so throughout the experiment.
Skill A
Analysing Evidence
Conclusion
My Results do not agree with my hypothesis. For some reason the line is not entirely straight and so I have drawn a curve of best fit to show that the data is not entirely correct. I think that this was due to the wire being warmed and so the resistance decreased and therefore I did not get an entirely accurate set of results. However these results do not entirely disprove my hypothesis and so further work would have to be done to check my hypothesis.
Just because your results are not what you expect does not make them “incorrect” – they simply do not agree with your hypothesis, but can be explained.
Skill E
Evaluating Evidence
Evaluation
Although the line was not straight, I still believe that my hypothesis was correct You can’t say this! What was the point of doing the experiment if you are going to ignore the results? You have explained above why you think the line was curved (yet a couple of lines down from here you give a DIFFERENT reason) so your evaluation needs to tackle how you might be able to stop or reduce the increase in temperature and so I would have to do repeat the experiment again to prove this. I think that the inaccuracy of my results was due to the fact that the range of results was not wide enough. To counter this I should have used a longer length of wire each time so that the results would have been greater. Also I should have repeated the experiment maybe five times to completely eradicate any wrong results.
Improvements on my Method
If I did redo the experiment I would use the same material and equipment. I would increase the length to 100cm and do the experiment 5 times, using a different set of wires each time so that the experiment becomes a lot fairer Your test WAS fair. In any case, repeating it does not make it fairer, just more accurate and proves that my hypothesis was indeed correct.
Further Work
In order to test my results even further I could repeat the experiment, but with different materials, such as copper or nickel, so that I can see if the same factors affect all wires in the same way. I could also investigate a different variable, such as the effect of temperature on the wire so that I could work out a formula for the resistance of a length of wire of any material. Investigating a different variable does NOT provide extra evidence, it is a different experiment. Leave the last sebtence out and instead give more details of how you would do the experiment with copper and nickel, e.g. what lengths of wire, what current etc.
