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
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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.
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 (?) 100 1.77 2.17 1.22 90 2.13 1.93 0.90 80 2.10 2.97 1.39 70 2.30 2.03 0.88 60 2.64 1.97 0.74 50 2.76 2.04 0.73 40 3.11 1.94 0.62 30 3.05 1.85 0.60 20 4.50 1.69 0.37 10 5.69 1.45 0.32 2. Length of wire (cm) Current (a) Voltage (v) Resistance (?) 100 0.50 0.60 1.20 90 0.54 0.59 1.08 80 0.58 0.57 0.98 70 0.65 0.55 0.85 60 0.71 0.53 0.75 50 0.81 0.50 0.62 40 0.94 0.46 0.49 30 1.06 0.41 0.39 20 1.32 0.31 0.22 10 1.74 0.23 0.12 3.
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. ?? ?? ?? ?? Katarzyna Lakus Page 1 5/10/2007
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