I predict that every time I increase the length of wire, resistance will also increase. This is because the longer the conductor, the more particles there are in the way. Therefore, electrons find it hard to flow.
Method
For this experiment I will use the following equipment:
- A power supply unit
- An ammeter
- A voltmeter
- 1m of Constantan wire
- Connection wires
- Crocodile clips
- A 1m ruler
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First I will connect the equipment in a series circuit with the voltmeter parallel, like the one below.
- Then I will turn on the power supply unit and set it to approximately 6 volts, this will be a non-variable voltage, I will not change it.
- I will then take my first reading of the ammeter with the crocodile clips just 5cm apart along the wire. I will then make nine more readings, each time moving the crocodile clips 5cm further apart. I will take each reading three times and use the average ammeter reading for my graph.
- I will also record the voltmeter reading to make sure it is always the same throughout the experiment.
Results
Analysis of results and conclusion
I can see a pattern in my results, it is very clear in the graph. It definitely shows that the longer the constantan wire, the less the current in the circuit. I know that current is inversely proportional to the resistance, therefore the longer the wire the more the resistance. This supports my prediction.
The curve of the graph reflects this inverse proportionality. The graph never touches the x axis because no matter how much constantan wire you put in the circuit, there will still be some current, even if a small amount. There can only be no current flow in the circuit if the circuit itself is broken.
Evaluation
I believe that my results are accurate because I tried to make sure that I kept everything in my experiment as fair as possible. I used a power supply unit instead of batteries because you can control the voltage on a PSU and batteries can run out. I also made sure the wire was accurately measured and all the connections were well secured. I did every test three times and used the average result in my graph. It is probably because of these precautions that I didn’t get a result that looked out of place.
I think I could have improved this experiment by changing the constantan wire for each length. I think this would improve my results because I know that the resistance of something can depend on its heat. So if I use the same 1m wire for the 5cm and 10cm tests, the results will not be as accurate as they would be if I had used completely different wires. This is because when I used the same length of wire for doing the 10cm test as I did for the 5cm one, half of the wire was quite hot and I think this would alter the resistance. But I think this would only make a small change to my results.
Overall I think that my experiment was successful and I have proved my prediction.
