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Investigating the Factors that may affect the Resistance of a Piece of Wire

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Introduction

Investigating the Factors that may affect the Resistance of a Piece of Wire

        The reason for performing this experiment is to investigate the factors that may affect the resistance of a piece of wire.  I began by doing some research about the factors that may affect the resistance of a piece of wire so that I could perform a safe and practical procedure.  (See “Textbooks”).

Firstly I started to carry out an experiment to find out firstly which wire with the bigger resistance, (constantan or copper), and then I had to find out which thickness of wire would be best suited to this experiment, 28 swg, 30 swg or 32 swg.  For example, I may choose copper because it has a greater resistance and 28 swg thickness of the wire because the resistance of the wire is not too big and not too small.  As the thickness of the wire increases the resistance increases, and as the thickness of the wire decreases the resistance decreases.  

Planning

Variables

There are a number of variables that I could use for my experiment, such as:

∙        Changing the voltage.

∙        Changing the current.

∙        Changing the thickness of the wire.

∙        Changing the length of the wire.

∙        Changing the material of the wire.

∙        Changing the temperature.

        These variables are all viable to use except changing the temperature of the wire because this is very difficult and time consuming.

...read more.

Middle

The Length of Constantan

Voltage, V

Current, A

Resistance, Ω

Width, swg

Length, cm

1.14

0.89

1.28

28

30

1.28

0.75

1.78

28

40

1.40

0.64

2.19

28

50

1.45

0.58

2.50

28

60

1.52

0.50

3.04

28

70

1.56

0.45

3.47

28

80

1.62

0.41

3.95

28

90

1.65

0.38

4.34

28

100

I decided to have a range of the length of wire from 0 cm-100 cm in the actual experiment to make the experiment fair.  I would also keep the potential divider the same and not move it to make the experiment fair.  Also take make the experiment fair I did it in one lesson and kept the same equipment.  If I changed the equipment or anything else my results would be distorted and wrong.

My Chosen Variable

After performing my pilot experiments I decided to use “Changing the Length of the Wire” as my variable because it is not a very complicated procedure but on the other hand, “Changing the temperature of the wire” is time consuming and very hard to do.  

Prediction:

        I predict that if I should alter the length of the wire or the thickness of the wire then the resistance should also change.  For example if I increased the wire length then the resistance would increase and if I decreased the wire length then the resistance would also decrease, I will explain this in my theory.  The resistance should double as the length doubles e.g. 10cm-1Ω, 20cm-2Ω and so on.

Theory:

As the electrons drift down the wire they bump into the lattice ions and bounce off.  This causes the resistance of the wire.

...read more.

Conclusion

Theory

The theory is partly explained in the prediction.  In all metal wires there are millions of moving electrons.  The reason that they move is because of electricity.  The resistance of a wire is caused when atoms that make up any object slow the electrons down.  This means that if there are more atoms to get in the electrons way (e.g. length or the width is increased) the resistance is then increased.  If there is twice the length of the wire, then there will be twice the resistance.  This will lead to there being double the number of collisions between the electrons and the atoms increasing the resistance by 2.  If there are 250 atoms blocking electrons in a 5 cm length wire then (according to my theory) there will be 500 atoms blocking electrons in a 10 cm length wire.  My theory explains why the results were directly proportional.

     My results that I have collected support my prediction because I said that if I increased the wire length then the resistance should increase and if I decreased the wire length then the resistance should also decrease.

The results have shown that this is true.  My graph of results shows that the line of best fit has followed the predicted pattern and that, although one point is very slightly anomalous to the rest, the gradient of the line stayed the same throughout.

Evaluation

Accuracy:

        From looking at my graph of results I can see that none of my points are extremely anomalous.  This shows that my results are accurate and that my apparatus which I used was also accurate

...read more.

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