physics potato osmosis
...eriment effectively has not been given to us. 4) The cross sectional area of the wire (the thickness) This will cause resistance to decrease because of the increase in space in the wire. The increase in space means that there is more space for the electrons to flow freely because there would be fewer collisions with atoms. I could do this by using different widths of a wire; for example thin, medium, or thick copper could be used. To begin with I am going to investigate which materials put up the highest resistance and I will combine it with the investigation about which length puts up the greatest resistance. Prediction I predict that, the longer the wire is, the more resistance there will be due to more collisions between the electrons and atoms. The length of the wire should be approximately proportionally the same as the resistance. In theory, if the wire is doubled, then so will the resistance. If the length is twice as much, then there will be twice as much collisions, which would increase the resistance. To make a more accurate prediction I did an experiment to show what things I am going to use in the final experiment. It will determine what lengths and factors I will use and make the experiment more reliable. The experiment The length of the wire experiment would be very easy to do, and give accurate results. Because of the length being proportional to the resistance, I could link the length of a wire with the resistance of the wire, which would make my graph more interesting. Due to the simplicity of this method, I have decided to use the length of the wire as the factor that I am going to use Apparatus · Crocodile clips · Ammeter · Voltmeter · Power supply · Meter ruler · Connecting wires · Sticky tape · Copper wire This is the circuit we set up. The method I used copper wire for this experiment to see the whether the material the wire was made out of made any difference. There is a ruler on the bottom with the 1m length of wire laid across it. There were crocodile clips attached on either end so I could move them up and down the wire and vary the length. I set everything up and started. I kept the amps the same all the way through each experiment, the first was at 0.3 A. I moved the crocodile clip 10cm down the wire and took the voltage at each one. I wrote these down then repeated the test and worked out the resistance. I worked out the resistance using the formula: R=V I To make sure the two experiments are fairly undertaken, the following must be done: When doing experiment one the room temperature must not be changed dramatically - because temperature effects the resistance of the wire, The current must be kept the same - so that each length of wire has the same amount of amps passing through it because The same amount of amps will also be used for experiment two, The power unit must be kept at the voltage - so that the current can be kept the same, Obtaining evidence Table of results AMPS LENGTH (CM) VOLTS VOLTSx2 AVERAGE RESISTANCE 0.3 100 0.06 0.06 0.06 0.2 0.3 90 0.06 0.05 0.055 0.18 0.3 80 0.07 0.05 0.06 0.2 0.3 70 0.05 0.05 0.05 0.16 0.3 60 0.05 0.04 0.045 0.15 0.3 50 0.04 0.04 0.04 0.13 0.3 40 0.04 0.03 0.035 0.12 0.3 30 0.03 0.02 0.025 0.08 0.3 20 0.03 0.02 0.025 0.08 0.3 10 0.02 0.01 0.015 0.05 These are the results I got. You can see by the table that the resistance slowly decreases with length. But I don’t think that there is a big enough drop in resistance between each length so I will change the type of wire and see if I get a more definitive change. The next wire I used was Constantine. I carried out exactly the same experiment as the first but changed the amps to 0.15. AMPS LENGTH (CM) VOLTS VOLTSx2 AVERAGE RESISTANCE 0.15 100 1.38 1.36 1.37 9.13 0.15 90 1.21 1.26 1.235 8.23 0.15 80 1.06 1.10 1.08 7.20 0.15 70 0.94 0.95 0.945 6.30 0.15 60 0.80 0.82 0.81 5.40 0.15 50 0.68 0.68 0.68 4.53 0.15 40 0.55 0.55 0.55 3.67 0.15 30 0.39 0.40 0.395 2.63 0.15 20 0.26 0.27 0.265 1.7 0.15 10 0.14 0.14 0.14 0.93 As you can see from this table, the resistance goes down almost by one ohm each time. This is a very good table and shows clearly that length definitely affects resistance. Now I will carry out another experiment using different factors but still using Constantine wire. This experiment was carried out using Wire 32. And once I had realised that Constantine wire provided better results I stuck to it. Also to obtain more results to plot a graph with I decided to move the crocodile clips down every 5cm instead of every 10. These are the results I got with this experiment: AMPS LENGTH (CM) VOLTS VOLTSx2 AVERAGE RESISTANCE 0.2 100 1.76 1.81 1.785 8.925 0.2 95 1.72 1.67 1.695 8.475 0.2 90 1.60 1.63 1.615 8.075 0.2 85 1.54 1.51 1.525 7.625 0.2 80 1.46 1.46 1.460 7.300 0.2 75 1.35 1.32 1.335 6.675 0.2 70 1.26 1.25 1.255 6.275 0.2 65 1.18 1.18 1.180 5.900 0.2 60 1.08 1.06 1.070 5.350 0.2 55 0.97 0.99 0.980 4.900 0.2 50 0.90 0.91 0.905 4.525 0.2 45 0.81 0.81 0.810 4.050 0.2 40 0.72 0.71 0.715 3.575 0.2 35 0.62 0.63 0.625 3.125 0.2 30 0.54 0.55 0.545 2.725 0.2 25 0.44 0.46 0.450 2.250 0.2 20 0.37 0.37 0.370 1.850 0.2 15 0.27 0.28 0.275 1.375 0.2 10 0.19 0.19 0.190 0.950 0.2 5 0.10 0.10 0.100 0.500 With these results I made a graph and drew a line of best fit. I did the experiment twice as with each one to make sure the results were as accurate as possible. There were no anomalous results. I will use what I have found out here to analyse and draw conclusions. As I said before, I drew a graph, plotting resistance against the length of the wire. I found that the points were very good and lay very neatly along the line of best fit. There were no anomalous results that stuck out, but if there were I would have repeated them to make sure that they corresponded with the other results. The results I thought were very good as they clearly showed how length is proportional to the resistance. This is a diagram showing how the length affects the resistance. From the diagram I can see that when the length of the wire is double (from X to 2X) there are other changes that also o...