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# The affect the length of a wire may have on the resistance.

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Introduction

The affect the length of a wire may have on the resistance. Aim: The aim of this investigation is to discover how the different lengths of wires affect the amount of resistance. Prediction: Metals are good conductors of electricity as electrons are able to move about within them. My research has shown me that this is because the outer electrons of the atoms within the metal are 'de-localized', meaning that they are able to 'swap around' with each other. If electrons are pushed into one end of a piece of wire, they will displace some of the electrons already present in the wire, with the effect that some of them will be forced out of the other end of the wire. However, while the electrons are moving down the wire, they are constantly colliding and interacting with each other. With every one of these collisions, just like a ball bouncing off a wall, as the electron loses a small amount of its energy, which is given off as heat. This effect is called resistance. If you add potential difference to a circuit, the electrons receive and gain energy. With this energy they move through the wires from positive to negative. The conductivity of the metal has no effect on the overall resistance. The reason for this is that there are always going to be atoms in the path of the electrons, resulting in the current being slowed down. ...read more.

Middle

> To make sure that the best results are obtained; I will record the current and voltage taken from the voltmeter and not any readings from the power pack. As these will be more accurate. I think that this method is appropriate conducting this experiment. It will enable me to obtain accurate results. The reason I believe this is that all the variables are kept at a constant level, except for the length of the wires. Fair Test: In order this experiment to be conducted in a fair and accurate manner: the following things need to be taken into account: - * Identical sets of equipment should be used wherever possible. E.g. crocodile clips and wires. This is required as these factors can have an effect on the resistance. * Only one variable should be changed. * Use a 300-mm ruler each time. Making sure that the length of the wire is cut to the nearest millimeter. * The same material of wire will be used throughout the experiment. This is nickel-chrome. * Make sure there is no magnetic fields surrounding the equipment. This can have an effect on the resistance. Results: Length of the wire (cm) Resistance (?) Current (C) Voltage (V) 1 0.15 4.90 0.73 2 0.25 2.90 0.97 4 0.43 2.95 1.28 6 0.65 2.26 1.47 8 0.85 1.90 1.61 10 1.08 1.55 1.67 12 1.31 1.33 1.74 14 1.51 1.18 1.78 16 1.66 1.09 1.81 24 2.54 0.75 1.92 Conclusion: I can see a trend in the results that I have obtained. ...read more.

Conclusion

For my experiments to give valid results, they had to be 'fair tests' in which only one variable was altered at one time. By doing this it is reasonable to assume that any change observed is due to that variable, and nothing else. The problem that I expected to be the most significant was that of the 'heating effect' caused by passing an electric current through a wire. Since the energy lost by electrons given out as heat, the temperature of the wire will increase, and since the resistance of a wire increases with temperature, this would introduce another dependent variable. I had thought of various ways that I could get over this problem, including making the wire into a coil and putting under running water from a tap. However, my preliminary experiments showed me that passing the current through the wire for the few seconds necessary for me to take my readings, no discernible change in resistance was seen. Even when passing the current for as long as ten seconds, I was unable to see any change in the readings for the current and voltage, indicating that there was no appreciable change in the resistance. To extend my investigation even further now, I could investigate different types of wires and see how they affect its resistance. I would also repeat the experiment to see if the results I obtained where constant and accurate. Overall this investigation went according to plan. I had no anomalous results and they were reasonably accurate. The results backed up my predictions and enabled me to make a good conclusion. ...read more.

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