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Investigation into the resistance of a wire.

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Introduction

Investigation into the resistance of a wireimage00.png

        In this investigation I will try to find out how the length of a wire affects resistance. I will make sure to keep the type of wire, diameter of the wire, voltage, and approximate temperature constant so the data I collect will be valid.image01.png

Also I must be careful about safety when working with electricity. Since we are testing for resistance we must be careful that the wire does not over heat and burn us or melt. We can avoid this by having a small voltage which reduces the heat loss in the wire and thus the risk of burns.

Equipment List:

Standard copper wire

Ammeter

Electronic Voltmeter

Battery

Constantan wire 70-10cm

The circuit I will use has an ammeter to read the current across the whole circuit and a voltmeter to measure the voltage across the wire. From this using Ohm’s law I can work out the resistance.

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Middle

Resistance (R=V/I) (Ω)

70

1.28

0.4

3.175

60

1.27

0.45

2.82

50

1.24

0.55

2.254

40

1.17

0.65

1.846

30

1.07

0.8

1.337

20

0.96

1.15

0.834

10

0.68

1.6

0.418

We then repeated the experiment to get very precise results.

Experiment 2

Length of wire (cm)

Voltage (V)

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Conclusion

As you can see in setup 1 the electrons flow for the actual length of the wire rather than in 2 where about 1cm is missed out. Although this seems like a small amount its is 10% of the total length if the wire is only 10cm long. These kinds of errors are cumulative and can produce very erroneous results.

        If I were to do this experiment again would make sure to attach the crocodile clips properly as in setup 1 also to try and regulate the temperature of the wire after each length of wire I would immerse the wire in a water bath. This is because if the wire is left standing the heat has often not dispersed by the time the experiment is setup again. Also using electronic multi-meters for both current and voltage eliminates human error. For example on a conventional ammeter it is often hard to differentiate between decimal points.

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This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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