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Investigating the Resistance of a Wire when Changing the Length.

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Introduction

Investigating the Resistance of a Wire when Changing the Length

Planning

In this experiment, I will be looking at how the length of a wire will affect the size of its resistance. I will do this by measuring the current (using an ammeter) and the voltage (using a voltmeter), and calculating the resistance using Ohm’s Law:

RESISTANCE = VOLTAGE ÷ CURRENT

                                          (       )              (V)               (A)              

To make this investigation a fair test, (by which I mean an experiment where only one variable is changed, and the other(s) stay the same), I will only change the length of the Constantine wire, with a Standard Width Gauge of 36. I will keep the voltage constant, at 2 Volts, and I will measure the current, to determine the resistance using Ohm’s Law.

I have chosen not to change the voltage, because if the voltage is set too high, then it may cause the wire to heat up, and this will give the wire more energy. If the wire has more energy, then it could cause the electrons to move quicker, and the resistance will be lower, by no cause of the rise in Voltage.

The apparatus I will use will be a 1-metre length of Constantine wire, numerous other crocodile clips and electric wires, a metre long ruler, an ammeter, a voltmeter and a Power Supply.

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Middle

0.45

2

30

0.35

2

35

0.30

2

40

0.27

2

45

0.25

2

50

0.21

2

55

0.20

2

Current and Voltage Reading Set 3

Length of Wire (cm)

Current (A)

Voltage (V)

10

1.05

2

15

0.71

2

20

0.55

2

25

0.45

2

30

0.36

2

35

0.31

2

40

0.27

2

45

0.25

2

50

0.21

2

55

0.20

2

Current and Voltage Reading Set 4

Length of Wire (cm)

Current (A)

Voltage (V)

10

1.00

2

15

0.70

2

20

0.55

2

25

0.45

2

30

0.38

2

35

0.31

2

40

0.27

2

45

0.25

2

50

0.21

2

55

0.20

2

Current and Voltage Reading Set 5

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Conclusion

When I worked out in my experiment what the resistance of 1m of Constantine wire is, it was different to that on the Focus on Science program. This could be down to many things I mentioned earlier during the Evaluation. When they did their experiment, they would have made sure that there would be no other factors effecting resistance, but in mine, this would not have been possible because I did not have the facilities to.

On the whole, the graph of average resistance follows the pattern that I expected it to, but with a chance, I would like to do it again, and hopefully get a better graph out of it. If I could do it again, I would like to, because I could see if my experiment was correct, rather than seeing what problems there were in getting the results out of it.    

Ryan Edwards

...read more.

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