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Investigation into the resistant in wires.

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Introduction

Physics SC1 Oliver lamb Investigation into the resistant in wires Aim: to investigate how the length of a wire affects the resistance. Apparatus: Wire (SWG 25) Ammeter Power source 4v Crocodile clip Variable resister Meter ruler Voltmeter Leads Method: Set up the apparatus as shown in the circuit diagram below. The length of the wire is changed between 0cm and 100cm at 5cm intervals. The current needs to be kept at a constant of 0.3 amps throughout the experiment and the voltage across the wire at each length of wire is recorded. The experiment is repeated 3 times with each length of wire, and an average obtained. If any obvious anomalies occur, then these are repeated also. Prediction: I predict that the longer the wire, then the greater the resistance. Conductivity of a metal depends on the numbers of free electrons, which are contained within it. The more free electrons, the more conductive the metal is, as the free electrons are given energy and then collide with neighbouring free electrons. This happens throughout the wire and electricity is conducted. Resistance is a result of energy lost as heat, and is measured of how much is lost in this way. Free electrons colliding with fixed particles within the metal, other free electrons and impurities cause the loss of energy. ...read more.

Middle

40 0.3 1.02 1.01 1 1 45 0.3 1.14 1.15 1.14 1.143 50 0.3 1.32 1.32 1.33 1.333 55 0.3 1.4 1.4 1.4 1.4 60 0.3 1.56 1.56 1.57 1.563 65 0.3 1.66 1.67 1.65 1.663 70 0.3 1.8 1.81 1.8 1.803 75 0.3 1.92 1.91 1.92 1.923 80 0.3 2 2 2.1 2.003 85 0.3 2.15 2.14 2.15 2.153 90 0.3 2.34 2.34 2.34 2.34 95 0.3 2.45 2.45 2.46 2.453 100 0.3 2.56 2.56 2.56 2.56 Observations: We will observe the reading on the voltmeter change as we change the current to .3 A. we also observe a general increase in the voltage as the length of wire we use gets longer. The variable resistor will also be set at different positions for the different lengths of wire that we use. To make sure our overall values are as accurate as possible we will repeat our readings 3 times and then take the mean resistance of the 3 readings. We will also be able to spot and Analysis Trends: From the graph we can see one very clear trend, which is, as the length of the wire increases so does the resistance of it. Another, more significant thing is that it the increase is constant. ...read more.

Conclusion

Most errors in our experiment were encountered in the measuring of the wire. This is because it simply was not very practical to hold a piece of wire straight, whilst holding it next to a ruler and then trying to accurately fix crocodile clips to the right part on the wire. Also I do not feel that the crocodile clips were always fixed securely to the wire with a good connection. This also meant that they were easy to move about on the wire changing the length of it. Errors rarely occurred in the setting of the current and the reading of the voltage. It was just in the preparation area that they did occur. Another example of this is the wire was never totally straight when we started the experiment, which may also, as said earlier on, affect the resistance of it. I do not think that doing any more results in our experiment would have made it any more accurate. I feel that the only way to make it more accurate would be to use a different method - perhaps were we had a bar that did not bend in place of the wire. We could even use a rheostat in place of the wire, because it is essentially a long coiled wire that is connected at different lengths to change the resistance of the circuit ...read more.

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