Does the length of wire in a circuit affect the resistance? Plan The aim of this investigation is to find out whether the resistance increases or decreases as the length of wire increases. The key factor that I plan to investigate is the length of wire, and I will alter the lengths of wire, and measure the resistance during the investigation using an ammeter and a voltmeter. The diagram above shows wire in a circuit. The current is hitting the wire particles, which slow the current down.
I predict that the longer the wire, the higher the resistance and the lower the current. The reason for this prediction is that when the current goes through a wire, the current hits the particles of the wire, which slow it down over a longer period of time. The path of an electron is not just a simple direct route from negative to positive, but an electron has a zigzag path, as electrons constantly collide with particles of wire. So the more collisions there are, the more friction there is, acting as the opposite force, and therefore slowing the current down.
If we have a longer wire, we are forcing the current to go through a wire-full of particles for longer; therefore the current will slow down after hitting more particles inside the wire. Ohms law states that the higher the temperature, the higher the resistance. As the friction increases heat, the atoms in the material start to vibrate more, as in the kinetic theory, an increase in temperature causes the particles to obtain more energy, and that energy is transferred into movement.
After taking into account all the above scientific information, I believe and predict that the longer the wire will be, the higher the friction0, the higher the resistance and the lower the current. To guarantee the best results I will use equipment that is quite accurate and simple to collect results from. I am going to use an ammeter and a voltmeter, and from the results given by them I will calculate the resistance using this simple formula:
Resistance = Voltage Current The equipment I need for this experiment is: > Voltmeter, > Ammeter, > Power pack, > Metre rule, > Conducting wires, > Crocodile clips,> Calculator. I will attach a section of wire on a meter rule, using sticky-tape at two end points of the wire to secure it. I will use wires to connect the wire to a power pack, and clip crocodile clips onto the wire. I will add a voltmeter in parallel to the wire, and an ammeter in series between the power pack and wire. When I switch the power pack on, I will wait only until the reading an ammeter and voltmeter stabilises, as I do not want the wire to heat up. I will keep this circuit simple to avoid confusion and anomalies. I will do this as in my preliminary experiment, I did so and this set up worked.
I will also ensure safety by making sure everyone wears lab coats, not overloading the circuit, and that no water or chemicals are placed near the circuit. Because I am measuring resistance I will have to try and keep the other variables that affect it constant. These include the voltage, the type of wire, the width and material of the wire, and temperature of wire. Therefore I will measure the wire at different lengths at the same voltage, keep the material of the wire the same all through the experiment, and leave the wire for a couple of seconds to let it cool down.
I will also use the same method to obtain every reading. Just in case, I will carry out the experiment in the same room, at the same room temperature, to be sure that the surrounding temperature did not affect my experiment. I will also repeat the experiment, and do it three times in total. I would like to collect as much readings as I can, so I will take readings every ten centimetres. This would mean that I would see a clear pattern.
Observations 1. Length of wire (cm) Current (a) Voltage (v) Resistance (? ) Resistance (? ) the average resistance for all three experiments is: Length of wire (cm) Average resistance Analysis All the results seem to start at the same place, but then they differ from each other. I think that the average graph is reliable until the point of eighty centimetres. The above results show that the longer the wire, the higher the resistance. In the graph there is a clear diagonal line, and although it is slightly wavy, it increases steadily.
This shows that there is a relationship between the length of wire and the resistance, and if you increase one of them, the other one also increases. The above evidence supports my prediction to the extent where the line drastically rises then dips at eighty centimetres. The valid scientific analysis would be that at eighty centimetres there is either an anomaly, or the wire grew too hot and slightly melted. This experiment was carried out in conditions where I did not have the resources to accomplish it professionally and exactly.
While we were doing this experiment, our ammeter was going haywire halfway through the experiment, so we had to change it. This could be a reason why our results did not for a perfect curve or line, yet continued upwards in a zigzag fashion. Evaluation The evidence obtained was quite accurate, however it is possible for a few anomalies to be found. This might be because of the equipment used, as it was borrowed from the school, or it could be because the wire did not have enough time to cool down, and the results were under the influence of heat, and therefore friction.
To improve this experiment I would set up a few of circuits that are exactly the same, using the same wire that is cut into metre long fragments. Then I would use them one by one on each length to avoid the heating of wire. Another way to improve the experiment is to use laboratory equipment instead of equipment designed for school use. I would have done it this way, but we did not have the resources to do this in the unsafe environment of a classroom. The evidence I have collected is not very reliable because the scientific equipment used in schools can never be as accurate as scientific equipment used in laboratories.
Additional evidence could be finding the relationship of resistance through different widths of wire, but for this experiment you would have to get different wires, and possibly create different circuits. In conclusion: I think that the investigation was realized in the best way possible, giving the time deadline and resources. I am sure that if we had more accurate and new equipment available, these results would all be on the line of best fit. My prediction was correct, as the line does go upwards revealing the link connecting resistance and length of wire: if one increases the other increases as well.