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Investigate the resistance of a wire at different stages on the power supply.

Extracts from this document...

Introduction

Planning

This is the part of my coursework where I am going to plan an experiment that I am to analyse for my work. What we are going to do is to investigate the affects or the variables have on different lengths of constantan wire. I am going to use different lengths which will provide me with a range of results. The reason I want a range of results is so that I can compare and analyse results, which will let me evaluate the readings clearly. First I will tell you a little about how I started. We were set into groups with other pupils, and then together we set out and did our preliminary experiment. The preliminary experiment is very important, because it is like a practice for the real thing. Also it helps as here you can make mistakes, so when doing the real experiment errors can be eliminated. I will explain how we did the preliminary experiment and include all the steps we took.

For my introduction I want to start off by just explaining a little about the material that we are using, as this is vital so we know what is harmful and what is not, which can help with safety.

The power supply – we will be using one of these. This can be dangerous if not used safely. We should know that the power supply should not b left on for more than a few seconds, with certain wires, as it can blow the system. When plugging the plug in, you must make sure the switch is off. This may sound obvious, but is a safety regulation. Also you should never plug the plug in to the socket if your hands are wet, as you may end up experiencing an electric shock.

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Middle

30

1.67

0.63

2.651

20

1.64

0.70

2.343

10

1.43

1.35

1.060

C38

SWG – 36

Diameter/Thickness – 0.20mm

At 2 Volts

Length (cm)

Volts (V)

Amps (A)

Resistance (Ώ)

100

1.90

0.11

17.273

90

1.87

0.12

15.583

80

1.85

0.13

14.231

70

1.71

0.14

12.214

60

1.82

0.18

10.111

50

1.83

0.20

9.150

40

1.75

0.28

6.25

30

1.71

0.33

5.182

20

1.60

0.42

3.810

10

1.52

0.72

2.111

C44

SWG – 24

Diameter/Thickness – 0.56mm

At 2 Volts

Length (cm)

Volts (V)

Amps (A)

Resistance (Ώ)

100

1.48

0.72

2.056

90

1.42

0.77

1.844

80

1.27

0.86

1.477

70

1.36

0.95

1.432

60

1.30

1.05

1.238

50

1.22

1.19

1.025

40

1.13

1.37

0.825

30

1.02

1.61

0.634

20

0.85

1.95

0.436

10

TOO

HIGH

To Calculate

C42

SWG – 28

Diameter/Thickness – 0.40mm

At 2 Volts

Length (cm)

Volts (V)

Amps (A)

Resistance (Ώ)

100

1.69

0.35

4.829

90

1.68

0.40

4.200

80

1.58

0.45

3.511

70

1.58

0.52

3.038

60

1.52

0.62

2.452

50

1.45

0.75

1.933

40

1.42

0.95

1.495

30

1.29

1.23

1.049

20

1.06

1.69

0.627

10

0.84

2.19

0.384

C41

SWG – 30

Diameter/Thickness – 0.31mm

At 2 Volts

Length (cm)

Volts (V)

Amps (A)

Resistance (Ώ)

100

1.79

0.26

6.885

90

1.80

0.29

6.207

80

1.78

0.32

5.563

70

1.77

0.37

4.784

60

1.72

0.43

4.000

50

1.70

0.52

3.269

40

1.63

0.63

2.587

30

1.56

0.84

1.857

20

1.47

1.15

1.278

10

1.35

1.56

0.865

Below are the results for my second variable, this is the thickness or the width of the wire.

Variable – Thickness of a Wire

Part No.

SWG

Diameter or Thickness in mm

Volts

Amps

Resistance

C38

36

0.20

1.75

0.23

7.609

C40

32

0.28

1.77

0.38

4.658

C41

30

0.31

1.70

0.52

3.269

C42

28

0.40

1.49

0.66

2.258

C44

24

0.56

1.22

1.19

1.025

C45

22

0.71

1.00

1.66

0.602

C46

20

0.90

0.80

2.17

0.369

C47

18

1.25

0.50

2.46

0.203

C48

16

1.60

0.38

3.02

0.126

All these experiments were done at 2V for safety reasons, using a silver wire each time to make the results fair.

I believe that I have enough data to make a conclusion; this is because I have chosen a wide range of wires to test on giving me more data. I believe that I made my test accurate by doing tiny things to my work to make it better. For example, I was extremely precise when cutting the wire to its exact measurement, so I was very precise. This would have been an unfair test if I wasn’t accurate and decided to measure free hand. That is just one example of why accuracy is vital when it comes to finding results.

I consider the results very clear, and it is easy to read. It can be interpreted and understood easily, all because the tables are clear and easy to read.  I also believe that my experiment with my group was very precise. The variables are suitably and are adequate enough to the investigation, because it is a way of measuring the resistance in a circuit, and I am investigating the affects of material on the resistance levels.

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Conclusion

The procedure I use I think was very suitable, because it was very precise and clear. Finding the resistance levels helped us to analyse the data. We could see which data affected the level of resistance, and others which had no influence at all.  The method I used was testing the levels of resistance by setting up a circuit, placing the wire into the crocodile clips and then using the figures from the volt meter and the ammeter, I used Ohms law to convert the numbers in to resistance, so I think this was pretty simple and I was easy to understand.

I think the quality of the evidence is very good, thankfully I can say that I did not make any errors, therefore I can say that there were no times were I needed to identify any anomalies. I did not make many errors at all through my work, so it was a satisfactory experiment.

I believe that my experiment was suitable as I said, but there are ways that maybe I could have improved on it. For example, I believe that if I had repeated my results just one more time, then possibly I would have more data, then I can compare using the same method, but this time I will have more to compare with.

I think that my method of analysing and results were reliable, because they justified the system as the results I got, I made substantially longer. I would like to add that I did my coursework very well, and it went well towards my predictions. The positive correlation in the graphs was something I wasn’t expecting, so things like this was good, as it was different.

...read more.

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