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# An investigation of the factors that affect the resistance of a wire

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Introduction

## An investigation of the factors that affect the resistance of a wire

Plan

Metals conduct electricity because the electrons in the metal can move about
inside the structure.
Wires can be made of different metals - and the reason why they give different resistances is all down to the number of  “free” electrons there are in that metal - these are electrons that aren‘t involved in bonding, and are “left over”. Current, is the flow of electrons around a circuit. Those materials, which have a lot of “free” electrons, will make it a lot easier for current to flow through, and so there is low resistance. That‘s why not all metals are equally as good at
conducting electricity.

The other things that can affect the resistance of a wire are length; a longer wire will make it more difficult for current to flow, as there is more material to travel through therefore the resistance increase. The cross sectional area; the larger this is, the more charge can travel at the same time through a given length, so the resistance decreases.

To calculate the resistance of a wire I will need to use the following formula:

Middle

15

0.78

1.30

1.67

20

0.62

1.34

2.16

25

0.50

1.36

2.72

30

0.42

1.38

3.29

35

0.37

1.39

3.76

40

0.33

1.40

4.24

45

0.28

1.41

5.04

50

0.24

1.42

5.92

55

0.22

1.43

6.50

60

0.22

1.43

6.50

65

0.22

1.43

6.50

70

0.19

1.44

7.58

75

0.18

1.44

8.00

80

0.16

1.44

9.00

Below is the 2nd set of results:

 Length of Resistance wire (cm) Current (Amps) Voltage (Volts) Resistance (ohms) 15 0.79 1.27 1.61 20 0.60 1.32 2.20 25 0.48 1.36 2.83 30 0.40 1.36 3.40 35 0.37 1.37 3.70 40 0.32 1.38 4.31 45 0.28 1.39 4.97 50 0.26 1.40 5.38 55 0.24 1.40 5.83 60 0.22 1.41 6.41 65 0.20 1.42 7.10 70 0.19 1.42 7.47 75 0.18 1.42 7.89 80 0.17 1.43 8.41

Below is the 3rd set of results:

 Length

Conclusion

I feel that the only way that I could have improved the practical to maybe make all the results exactly on the best line of fit would maybe be the aspect of the ruler. This is because contact with the wire placed on the ruler was only needed to record the results. This may have been where some errors or inaccurate readings were taken. So maybe measuring each piece of wire and cutting it to the required length rather than using the same piece and just changing the point of contact.

This evidence does support a firm conclusion as if someone was to repeat the same investigation I would expect the to receive the same results.

If I were to re-do the experiment, I would test the same factor again, but maybe test a larger range to see whether the pattern that I recorded in this experiment would be repeated. Or I could perhaps test a shorter length but as my preliminary results showed that the wire increased in temperature I would have to add a variable resistor. However I could change the factor I test altogether- I think I would pick to change the type of wire that the resistance wire was made of.

Katie Matthews        Physics        -  -

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