Elastictvy of Copper investigation

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Elasticity of Copper investigation

In this experiment I will investigate how the extension e of a length of copper wire changes as the stretching force F is increase. The question I will be answering is: “If a wire whose original length was L is subjected to a stretching force F then will the wire increase in length by the amount e

The aim of this experiment is to investigate how the extension of a length of wire is affected by the force. I will then find stress and strain after finding these variables, for which I can finally complete my objective which is to find the young's modulus for the material, in this case copper wire. My aim is to measure the extension in a piece of copper while consider safety precautions and accuracy. For the experiment I will have to also consider the accuracy of both my equipment and the degree of accuracy for my results. Furthermore I will have to find a suitable range of results so that I can form a reliable basis for my conclusion, also so to allow me to show a clear set of results on a graph so that I can identity the trend.

Hypothesis I predict that when a wire is subjected to a stretching force, in this case wire being pulled by the force of weight, then the wire likely to be stretched. This does depend on the material as the more flexible the material is the more possibility there is of stretching. I think that the copper wire will have a young's modulus of about 130 Gpa(GigaPascals / Kn/mm), as the secondary source has worked this out The stretching force which extends material by equal steps is called Hooke's law.

Hooke’s law states that the force needed to stretch a spring is proportional to the extension of the spring from its natural length. The formula used for Hooke’s law is Force, F=Ke. The K is the spring constant (measure in force by length) and e is the extension.

Based on Hooke’s law theory I predict the greater the value of K is the Stiffer the spring will become. Also for the graph of F against e, the line should be completely straight. The gradient of the straight line from the graph when drawn will be equal to K.

This is equation for Young Modulus and should be recorded by working out the gradient for Stress and Strain on the graphs I will make for the results

Searle’s Apparatus

The extension of a wire under tension may be measured using searles apparatus. The micrometer attached to the control wire can be adjusted so the spirit level between the control and wire is completely horizontal. When weights are attached onto the hinge , it extends slightly causing the spirit level to drop on one side. The micrometer is then adjusted to make the spirit level horizontal again. The change in the micrometer is therefore equal to the extension of the wire. The extensions are all measured for different weights which the tension increases as well as a result of higher mass on the wire.

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Stress and Strain

Strain is the deformation caused by the action of stress on a physical body. Strain is measured by calculating the change in length (termed the stretch or absolute strain) and comparing the stretch to the original length. Strain is positive if the material has gained length (in tension), and negative if it has reduced length (in compression). Strain has no units of measure but sometimes is given as a percentage. By calculating strain as a percentage we correct for the length of the object. In this experiment I will ...

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