My experiment is safe because all of the wires are insulated and have covered ends. To carry out the investigation I will:
1. Collect together the equipment needed,
2. Set it up as in the circuit diagram below,
3. Change the length at which the crocodile clip touches the wire,
4. Record my results each time,
5. Repeat the experiment a sufficient number of times.
I am going to measure the voltage and the number of amps flowing around the circuit.
Circuit Diagram
We worked very safely in this experiment, we did not need to wear goggles or eye protection because all the wires had covered ends on them and the equipment was safely set out on the bench.
We set up a circuit using the circuit diagram, then the teacher checked it before we switched it on.
When we measured our results we did it in a systematic way (i.e. 10cm, 20cm, 30cm, etc..).
We did the experiment three times to make sure that there were no anomalous results. We found a trend which said that, the longer the wire, the greater the resistance. We recorded the results in a table like this:
The results were definite enough because they showed what I had predicted would happen, and with no anomalies.
My results show that, as the length of the wire is increased, the resistance increases. This agrees with my prediction. I think it happens because, there are more atoms for the electrons to bump into - e.g. if there are n atoms in a piece of wire m cm long, then there would be 2n atoms in a piece of wire 2m cm long - so the longer the length, the more resistance the wire gives.
The pattern in my results is very clear, they show that, as you increase the length if a wire, the resistance of the circuit it is in increases. I think that my results are very reliable because the experiment was fair. The experiment was fair because I only altered one variable - the length of the wire - I kept the rest of them the same - e.g. the power supply, etc.. When I repeated the readings , they were almost identical, and this shows that it was not an anomalous experiment and that I could probably repeat the investigation again and find that the results are still pretty much the same. All of my results seem to fit neatly around the curve of best fit on the graph. To improve the reliability of my results even more, I could have repeated the experiment more than three times. This would give a more accurate result.
The results in my table and on my graph are not from a single experiment, they are an average from a set of three.
