The way I will calculate the resistance is:
RESISTANCE (Ohms) = VOLTAGE (Volts)
CURRENT (Amps)
Equipment
The following is all the equipment that I shall use:
-
Crocodile Clips
- Wire
- Voltmeter
- Ammeter
- Power supply
- Ruler to wrap the wire around.
Method
For this experiment I will set up a circuit using the items listed above. I shall set out the circuit, keeping the wire etc together using crocodile clips. I will first use a long piece of wire, then cut it short to change the length. I will use the voltmeter and ammeter to take the readings.
The circuit should be set up as it is shown in the circuit diagram above. It is important that the voltmeter is set up in parallel and the ammeter is vertical. The readings from the ammeter and voltmeter will be used to work out the resistance. This can be done using the formula:
R = V
I
Where V=voltage, I=current and R=resistance
Series
I will start the experiment with 100 cm (1 meter) of wire and go down in 10 cm till I reach 20cm. I’m doing this so I get a varied set of results.
The wire will be of medium thickness because if it was too thick then it would cause too much heat and there wouldn’t be enough resistance, and if it was a very thin wire there would be too much resistance and it would be too difficult to measure.
Will It Be A Fair Test?
It will be a fair test because the only thing I will be changing is the length of the wire and that will be changing by 10cm. I will be using the same equipment throughout the experiment and also use the same strength of electricity. The only thing that might affect the results is the wire being wrapped round the ruler as it will be hard to keep the same tightness and lengths round the ruler at all stages. I will repeat the experiment a few times so that I can get a average result and I no nothing drastic will have gone wrong in any of the tests.
Results Tables
I put the two results together to find an average set of results.
Conclusion
I have now concluded that I was right in my prediction, which was:
As the wire gets shorter the resistance will decrease with it and the longer the wire is the higher the resistance will be.
I have proved this by the two experiments that I did. The results both came out with reasonably straight lines, as did the average results of the tests.
Evaluation
Evaluating the Experiment:
I am quite pleased with how the experiment has turned out as the was no major mistakes made and the results were as I predicted and there were signs of the relationship between the length and the resistance in the results.
I didn’t really change my plan at all as it went as I wanted it to as I had set everything up correctly. Though I did find it quite difficult to read some readings of the voltmeter and the ammeter as the gaps were very small on readings such as (example) 2.3 etc.
I could have probably got a slightly better set of results if I had repeated the experiment another couple of times and then I would have acquired another average.
Evaluating my Results
Here again I am pleased with the end product. I do think that I took enough measurements, as I was able to obtain an average set of results. Therefore I was able to check my first test outcome and was also able to repeat it. Once I had repeated it I found that I got a similar set of results as in the first test, this meant that I had completed the first test using the right method.
I think that all of my results show a good relationship between the length of wire and the resistance as the follow the same sort of pattern. Not exactly on a straight line but along the outside a bit.