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Investigate one of the many factors, which determine the resistance of a wire.

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Introduction

Physics Coursework Investigation: Metal wires are used extensively to conduct electric current over long distances. I am going to investigate one of the many factors, which determine the resistance of such a wire. To my knowledge, in general metals are good conductors of electric current. The particle structure of a metal is as follows: 1. There are lots of atoms, which are arranged in a regular pattern. 2. The atoms are very close and there are strong forces of attraction between them. 3. The atoms are vibrating 4. The atoms have outer electrons, which are loosely held. (A p.d. can push these lose electrons to cause a flow of charge through the metal) The size of the electric current/ the resistance will depend on these factors of the wire: * The diameter * The temperature * The material * Density * The length * The P.d. Theoretical predictions about the above factors: Diameter - As it increases the resistance might decrease, as there is more space for electrons to flow. Temperature - The hotter the wire the more the atoms are vibrating and perhaps impending the flow of electrons. ...read more.

Middle

The resistance will be found by using the formula R= V/I At a chosen length the jockey will make contact with the wire and the results shall be noted down in a table like the one below. Length (cm) I (amps) V (volts) I (amps) V (volts) I (amps) V (volts) 5 15 25 For this to be a fair test all the other variable factors will need to be kept constant. These are: * The diameter * The temperature * The material * Density * The P.d. To test my hypothesis further I am going to test a different wire made of a different alloy. Also it has a smaller diameter (0.19mm) than the nichrome (0.45mm). I am changing 2 variables. By testing another wire I can compare it to my original and draw a more accurate and educated conclusion than I could using 1 set of results from a wire. Analysing and considering evidence The conclusion that I can draw from looking at my first graph - the nichrome wire- is that it has proved my hypothesis correct. The resistance in this wire does increase as the length does. ...read more.

Conclusion

There were not really any anomalous points on the graphs; they all seem to be quite consistent. 2. The wire may not of been perfectly straight. Thus the lengths at which results were taken may not have been what I thought. 3. The jockey might not of made good contact with the wire. To prevent this the wire needs to be kept constantly in the 'groove' on the edge of the jockey and the rest of the jockey on a steady surface. When a different length is then needed it should be 'slid' to the correct position. 4. Perhaps the ruler wasn't kept straight all the time. This problem could be resolved by selo taping the ruler to the piece of wood that the wire is on. This way it does not move. 5. When a wire is kept in the atmosphere for a long time it obtains an oxide layer. This oxide layer can increase resistance. To prevent this, fresh wire (one that has been shielded from the atmosphere) should be used for this experiment. If the resistance is proportional to the length, when the length is 0 the resistance should equal this. This is not seen on my graphs. There is some resistance at 0 length. This could be due to resistance in the circuit. ...read more.

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