I predict that as the length of the wire increases, the resistance will also increase. This is because it takes more energy to move electrons through the circuit.
I will ensure a fair test by keeping the length the same on each wire, I will do this by ensuring that there are no bends in the wire and that it is kept straight without any slacking. I will also keep the temperature the same, by not allowing the wires to get too hot.
Diagram
Results
Key: Black results = constantan wire
Blue results = eureka wire
To calculate the resistance you divide the p.d by the current
Conclusion
My results clearly show that as the length of the wire increased, the resistance also increased. This agrees with my prediction, as I stated that as the length increased it would require more energy to move the electrons through the wire. This has proven to be correct. These results also tie in to the scientific theory, as it is known that length affects the resistance of a wire.
We also tested another material as part of our investigation to see if this also affected the resistance of the wire. We used a wire called constantan shown on the results table in black, and a wire called eureka shown in blue. As the table shows there wasn’t a great difference between the two wires. The constantan wire had a slightly higher resistance but only by a small amount. Therefore this evidence is not really substantial enough to prove which of the wires affected resistance the greatest.
Evaluation
This investigation was highly successful as our results show, that the length of a wire does affect resistance. My prediction was correct, and our investigation agreed with the scientific theory that as the length increases the resistance will increase. This is due to the requirement of more energy to move electrons through the longer wire.
Our results support our decision as the graph shows. The Eureka wire was an accurate line of best fit with no anomalous results. The constantan results almost completed a line of best fit with only two results a fraction of the way out. They did not however go out of my theory; they still agree that the resistance increases along with the length. The reason for them not completing the line of best fit could have been because the wire began to get too hot, or because the wire was slacking a little.
However the majority of our results show that our investigation went well, and that we did not allow our wires to get too hot, and that we ensured a fair test.
There were only a couple of problems with our investigation that we were able to notice and improve without them ruining the results. To begin with we were keeping the power to our circuit on throughout the experiment, this was allowing our wires to get over heated and ruin the results. We noticed as the wire was burning through the selotape that we had used to stick it to the ruler. We then turned off the power and repeated the results that were incorrect. Another problem was that the wires we were using were too bent, which meant that it wouldn’t have been a fair test as the length wouldn’t have been correct. Again we repeated the incorrect results with a fresh piece of wire.
If I were to repeat this investigation I would make it more reliable by timing how long the power was kept on for to ensure that the wires never exceeded a certain temperature. I would also take more readings to see if the difference in resistance between the two different materials continued to increase, this would help me to decide whether the material did affect the resistance of a wire.
By Carla Hodgkins
