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How the length of a wire changes the resistance

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Introduction

How the length of a wire changes the resistance

The resistance of a wire depends on certain factors. Investigate the effect of one of these factors - Planning
Some variables that will be relevant to this investigation are:

* Length
* Thickness
* Temperature
* Voltage
* Material

Of these the variables will be length and resistance. The other variables (temperature, material and voltage) will have to be kept constant in both experiments to make sure that only length and resistance are investigated. The same bit of wire and the same thickness need to be kept constant. These factors need to be kept constant to make the experiment fair. If these were varied then the results, of the different lengths of wire, may be equal.

Apparatus

Wire (testing)

Wire (connection)

Amp meter

Voltmeter

Battery

Prediction


I predict that the longer the wire the greater resistance to electricity, and the shorter the wire is the smaller the resistance. This is because metals conduct electricity because the atoms in them do not hold on to their electrons very well, and so creating free electrons, carrying a negative charge to jump along the line of atoms in a wire.

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Middle


Results

Length (cm) V1 (volts) V2 (volts) A1 (amps) A2 (amps) Average resistance (Ohms)
   100                 1.00              1.00        0.20                0.20                5.00
     80                 1.00              1.00        0.30                 0.28                4.00
     60          0.90               0.90        0.40                 0.30                 2.80
     40                 0.90               0.85        0.50                 0.40                 1.94
     20                 0.70               0.80         0.80                 0.75                 0.94

 
Analysis

The graph of experiment 1 is a straight line through the origin, which means resistance is directly proportional to length. This means that if the length is 40cm, and

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Conclusion



I would also investigate other factors and see how these affect the resistance. I would also do the experiments under different conditions such as temperature and pressure to see if it makes any difference to resistance. As these results had a range of only 5 readings, from 0-100cm, and were only repeated twice, and that the results are not 100%, accurate due to the errors discussed earlier, then I would say that these results are not strong enough to base a firm conclusion on because there are so many sources of error, which are explained earlier. I would experiment with different lengths and types of wire.

John Hutton-Cornish

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