Prediction:
In this experiment, I expect that the resistance or why you depends upon
- Its length - the greater the length, the greater the resistance.
- Its cross-sectional area - the greater the area the less the resistance (GCSE physics by C. Boyle)
My prediction is that the length of the wire will be directly proportional to the resistance. I will make this experiment fair by performing investigation and each period ball at a time as not to forget the variable mixed up. For suitable results, I shall have to control the temperature in order to stop it from interfering with the investigation and changing the resistance.
Safety:
- I will make sure I don't turn the voltage on the power pack too or it will burn the wire.
- Before turning on the power pack, I will make sure all the connections are correct and there is no lose wire.
- If I smell burning, I will turn the power pack off.
Apparatus:
A table
1 x power pack (to give varied voltage)
1 x voltmeter
1 x Ammeter
5x Wires (with crocodile clips)
Wires of varied length
Circuit diagram
Ruler
Method:
I will set up the apparatus as shown in the diagram above.
The resistance is going to be recorded at 7 different lengths. I have chosen to record the results at this amount of lengths, as it will give me a much more accurate result at the end of the experiment.
As you can see in the diagram, I have chose to use a digital voltmeter instead of a conventional analogue voltmeter, as this can give me a much more precise result than an analogue meter. This is because the needle on an analogue meter could be bent and give me the wrong reading, but a digital meter does not involve needles, so would give a much clearer reading.
The way to calculate the Resistance relies on this formula:
Resistance = Voltage/current
I will use the voltmeter provided to get the voltage, and the ammeter provided to get the current (in amps).
Results:
20 cm
30 cm
40 cm
50 cm
60 cm
Average resistance:
Conclusion:
In conclusion, I have found that my prediction was correct. I said that the resistance will increase approximately proportionally to the length, and as you can see from the graph, this was correct. This is emphasised because the line of best fit is a straight line, which means the resistance is proportional to the length. This proves the fact that the longer the wire is; the more collisions there are between atoms and electrons. So if the wire increases in length, so does the resistance. If the wire decreases in length, so does the resistance.
Evaluation:
This experiment has gone satisfactory, but there have been certain things in the experiment that I have not been pleased with.
Some of my results have turned out anomalous. This mainly being:
60cm Anomalous
I have probably ended up with this anomalous result because of an error in recording my results.
However, as you can see from my average resistance graph, the results are roughly on the same line, so this anomalous result did not do much harm when the results are averaged.
I have noticed, now that I have finished my coursework, that there are a number of things I could have done to get more accurate results.
Firstly, I would do the experiment using the width and the material used as a factor too, just to make sure that my averages are as correct as possible