My prediction is that as the length of wire is increased the resistance will increase also; it will be directly proportional. This can be explained scientifically. Current is a free moving flow of electrons. Resistance reduces the flow of electrons. This resistance occurs when the electrons, that are attracted to the positive side of the cell, bump into the fixed lattice nuclei of the material that they are flowing through. This means the path of the electrons is erratic as they are changing direction. The more material there is for the electrons to flow through the more fixed lattice nuclei there are.
More nuclei mean more bumping and therefore higher resistance. Double the length of wire would mean double the amount of lattices for electrons to collide with. There will be a certain amount of lattices in a certain length of wire. These lattices will provide a certain amount of resistance. So when a wire is increased by the certain length, there will always be the extra certain amount of lattices and the resistance of the wire will always increase by the same amount. This means that resistance is directly proportional to length.
When the cross-sectional area of the wire is increased the resistance decreases. This is because there is more space for the same amount of electrons to move in. If I were to increase the cross sectional area in my experiment, I would expect the resistance to be less than a smaller cross-sectional wire of the same length. When temperature increases resistance also increases. This is because the extra heat gives the electrons extra energy. This extra energy makes the electrons vibrate. This in turn means that the electrons hit fixed lattice nuclei more often and therefore rate of flow is decreased.
Safety Specific to this experiment, voltage should not be increased to above 6 volts and power should not be left on for too long. This will prevent overheating and melting of the wire (overheating occurs when the kinetic energy of electrons is converted to heat energy on collision with fixed lattice nuclei). I will make sure that the wire is not touching anything before I turn the power pack on. I will also make sure that the dial is on 0 before I turn the power pack on reducing the risk of burning myself. Obvious rules such as no running in the science lab should also be applied. Fair Test.
Suitable factors to vary would be temperature, length, thickness/cross-sectional area, insulating or not and the voltage applied. Length, diameter and voltage would probably be the three most suitable as they are the easiest to vary. Temperature is hard to maintain, there are not that many easily available types of wire, and there would not be much range involved when using the insulation idea. Out of the three I choose length. To keep this experiment a fair test, I will keep all the other variables fixed. This will keep it a fair test because then every time I change the length, the other conditions will stay the same.
I will try and produce accurate results by testing each length three times and taking an average. Also any inconsistent/strange results will be discarded. I will also take care when I measure the length of the wire each time I measure it. Apparatus Five connecting wires, Terminal blocks, Rulers, Voltmeter, Ammeter, power pack. My range of results will be between 10cm and 100cm at 10cm intervals, I would say that this was an appropriate number of results (10) and they will also all have equal intervals. There is an option of recording resistance using either a multimeter or an ammeter and a voltmeter.
I used a voltmeter and an ammeter because a multimeter was not readily available to be used. Preliminary Results I carried out a preliminary experiment to see the other factors that could affect the experiment and also to see if I could improve any of the steps in the method. Using the Ammeter and Voltmeter: Apparatus Ammeter Voltmeter Connection Wires Wire attached to a meter rule Power supply Crocodile clips 1. Connect up apparatus as shown above. 2. Move the connecting wire that is not connected to the left end of the meter rule to the 10-cm mark. 3.
Record the current and voltage displayed on the ammeter and voltmeter. 4. Use “Resistance = Voltage / Current” formula to work out resistance. 5. Repeat steps 2, 3, and 4 for each length. 6. Remember not to touch the wire attached to the meter rule, as it could be hot. Preliminary Results Length Current Voltage Resistance Average Resistance 10cm 0 These are my preliminary results. These results tell me It is clear that the resistances for 0. 03A go up by 1 steadily, until 60cm when it then becomes irregular.
Out of all the results there are none that are the same but the results are quite close together. The currents that I chose could have been too low to produce good results, but the range that I used (lengths from 10cm to 100cm in steps of 10cm) was good because I got a wide variety of results. For these results I used Nichrome 28. I will use this diameter (0. 376) in my real experiment because I can get stable and reproducible results, E. g. at 20cm they are 2? , 2. 26? , and 2. 78?. I decided to use this method for my main experiment. This is because I think it is accurate and easy to use.
With this method you can work out the resistance yourself rather than leaving it to a machine, which could give inaccurate results if its battery was low. To make sure these results were reliable I would take an average of the results recorded, as I did for the preliminary experiment. This will help get rid of slightly bad results. Results Using Constantan 28 wire. Length Current Voltage Resistance Average Resistance 10cm Analysis.
I have found that when you increase the length of wire that current has to flow across, the resistance increases. I decided that graphs with best-fit lines were the best way to process my results and the best way to show my results clearly. The pattern in the graph is not so obvious; the line starts of straight but then at 30cm starts to go off on it’s on course. From then on, none of the points follow a pattern. But points to go from left to right, always in an upward motion – although somewhat erratically. These results definitely tell me that when the length of wire is increased the resistance increases also.