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Throughout this experiment I have decided that I am going to investigate the tensile properties of a Copper wire.

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Introduction

Physics Assessed Practical Experiment.

Jonathan Chown

AIM

Throughout this experiment I have decided that I am going to investigate the tensile properties of a Copper wire.   I want to investigate the stress, strain, young’s modulus, breaking point or maximum stress, yield strain.  I will also be able to investigate elastic and plastic properties in the material.  Stress is due to internal forces acting on the material and is defined as force acting on a unit area in M2.

Strain measures the ratio of the extension or deflection to the original length.

Young’s Modulus of Elasticity refers to the ratio of stress to strain and hence is equal to the gradient of a Stress vs. Strain graph below the elastic limit.

PLANNING

The material that I am going to use for this investigation is a copper wire.  Copper is a crystalline structure which means that it has a lattice arrangement with strong bonds, these bonds will have to be broken for the sample to be stretched and deformed.

The sample will be in a thin wire form.  This is because it will be easiest to work with and a long length can be used and worked with.  The advantage of this is that for a given strain the extension will be longer, hence able to be measured for accurately.

...read more.

Middle

4.50E-08

2.00E-01

2

4

44

1.5

2.6

4.50E-08

2.50E-01

2.5

5

55

1.9

2.6

4.50E-08

3.00E-01

3

6

66

2.3

2.6

4.50E-08

3.50E-01

3.5

6

77

2.3

2.6

4.50E-08

4.00E-01

4

8

88

3.1

2.6

4.50E-08

4.50E-01

4.5

12

100

4.6

2.6

4.50E-08

5.00E-01

5

22

111

8.5

2.6

4.50E-08

5.50E-01

5.5

37

122

14.2

2.6

4.50E-08

6.00E-01

6

51

133

19.6

2.6

4.50E-08

6.50E-01

6.5

75

144

28.8

2.6

4.50E-08

7.00E-01

7

120

155

46.2

2.6

4.50E-08

7.50E-01

7.5

175

166

67.3

2.6

4.50E-08

8.00E-01

8

250

177

96.2

2.6

4.50E-08

8.50E-01

8.5

250

188

96.2

2.6

4.50E-08

Area of sample =

The formulae that I needed to use for these calculations were as follows…

Area is equal to diameter divided by 2, squared and multiplied by TT.

Stress is equal to force divided by area.

Strain is equal to extension divided by original length.

I used scientific notation for the calculations, scales and data sheets because they allow smaller and larger numbers to be represented on a more concise scale and prevent the long numbers that are hard to visually understand and compare, let alone plot.

After calculating the stress and strain I plotted them on a Stress Strain graph.

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Conclusion

The plastic region of the graph generally follows the expected pattern for a stress strain graph.  The only strange result is the last point which is probably anomalous.  Reasons for this were discussed earlier.

There is a very large plastic region for this material; in fact the material has stretched by nearly ten percent before breaking.

If I was to conduct the experiment again I would take steps to increase the accuracy of my results.  These steps would include more repeats, trying the test without a pulley to eliminate risk of friction, and using a longer sample to make the results a little bit more manageable.  I would also use a vernier scale to record my results.

CONCLUSIONS

From my experiment I can conclude the following…

The yield stress for copper sample was 88MPa

The breaking point for the copper sample was at 250mm with a force of 8.5N acting on the sample.

The Young’s Modulus for the copper sample was 28 GPa

The copper sample stretched almost 10% of its original length.

The evidence for all of the above statements has been graphically presented and the conclusions were brought about by analysis of the graphics.

I have discussed problems, causes and improvements that could be made to my experiment but overall I am happy that I have sufficient evidence to support these statements.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Probability & Statistics section.

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