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Investigate how the length of a wire affects its resistance.

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Introduction

Resistance of a wire Coursework Plan Aim To investigate how the length of a wire affects its resistance. Theory A current is a flow of charge. Electric current is the flow of electrons, usually in a wire. A current comes from cells or batteries, the electrons are already in the wire but have no charge. Current is measured in Amps using an Ammeter. The Ammeter must be placed in series with any components because it measured the current passing through it. To make a current flow you need a voltage. A cell or battery provides voltage. It is the energy that is needed to move a certain amount of charge (electrons) between two places. Voltage is measured in volts using a voltmeter. The voltmeter must be placed parallel to components because it is measuring the energy the electrons use up as they pass through the component. Electrical resistance is the effect a wire or component has on a current as it tries to prevent the current flowing through it. The electrons in a wire flow through the wire but there is a chance that they will collide and be slowed down by an atomic nuclei, this is resistance. The resistance of a length of wire is calculated by measuring the current present in the circuit (in series) ...read more.

Middle

0.58 3.94 3.92 3.92 3.93 0.15 40cm 0.65 0.66 0.65 0.65 3.82 3.80 3.80 3.81 0.17 50cm 0.74 0.72 0.76 0.74 3.39 3.38 3.36 3.38 0.22 60cm 0.78 0.81 0.78 0.79 3.17 3.23 3.18 3.19 0.25 70cm 0.82 0.85 0.85 0.84 2.82 2.83 2.82 2.82 0.30 80cm 0.84 0.86 0.86 0.85 2.72 2.73 2.74 2.73 0.31 90cm 0.91 0.93 0.91 0.92 2.39 2.46 2.46 2.44 0.38 100cm 0.92 0.92 0.94 0.93 2.44 2.43 2.44 2.44 0.38 I took three sets of readings so my results were as accurate as possible. I then found the average of all three results (add all three up and divide by three) and used Ohms law (R= V/I) to calculate the resistance in the wire. Conclusion As I predicted, an increase in length resulted in an increased resistance. The wire shows a strong trend of a straight line, i.e. the length of the wire is shown to be directly proportional to the resistance- double the length and the resistance also doubles. The increase in resistance is due to the longer length of wire and the electrons, which make up the current, have to travel past more of the fixed particles in the wire. This causes an increased number of collisions and therefore a higher resistance. A Short wire A Longer wire From this diagram you can see that the longer wire has more nucleus for the electrons to bump into therefore increasing resistance. ...read more.

Conclusion

This would give me a wrong result because the vibrating nuclei take up more room and therefore will let fewer electrons through. Extending the investigation To extend the investigation I could extend the range of lengths investigated and to see if the observed trend continued. I could also test alternative wires such as constantan or nickel chrome. I would do this to see if when the length of these wires is increased if the resistance also increased as it did with copper. I think that other types of wire would have different amounts of resistance because different wires have different densities. A denser wire would have more resistance because its nuclei are more tightly packed together, so the electrons are more likely to bump into the nuclei, thus causing more resistance. However I think other wires would still display the same trend as copper did (Resistance is proportional to length) I think this because an increase in resistance is due to the longer length of wire. The longer the wire the more fixed particles the electrons, which make up the current, have to travel past. This causes an increased number of collisions and therefore a higher resistance. If I did this experiment again, I would measure the wire using a millimetre ruler to keep any wrong lengths to a minimum therefore my results would be more accurate. I would also make sure I had let the wire cook completely before starting the next experiment. GCSE Physics coursework 1 Lucy Simmons ...read more.

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