Copper Young's modulus

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Title:

Measuring Young’s modulus of copper

Aim:

To study the stress/strain behavior of copper wire and estimate the Young’s modulus of copper

Apparatus:        

Copper wire s.w.g.32        about 4 m

G-clamp        ×1

Wooden block        ×2

Metre rule        ×4

Pulley on clamp        ×1

Micrometer screw gauge        ×1

Hanger (0.01 kg)         ×1

Slotted mass (0.05 kg)         ×8

Slotted mass (0.1 kg)        ×6

Slotted mass (0.2 kg)        ×4

Slotted mass (0.5 kg)        ×1

White label sticker        ×1

Safety goggles        ×1

Rubber tile        ×1

Theory:

When a force F is applied to the end of a wire with cross-sectional area A along its length, the tensile stress =

If the extension of the wire is Δl, and its original length is lo, the tensile strain =  

Under elastic conditions, a modulus of elasticity of a wire, called the Young modulus E, is defined as the ratio of the tensile stress applied to a body to the tensile strain produced.  where E is expressed in N m-2 or Pascal (Pa).

E is a constant when Δl is small according to the Hooke’s Law which stated that the stress applied to any solid is proportional to the strain it produces for small strain.

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Therefore, when a material has a larger the value of E, it resists to the elastic deformation strongly and a large stress is required to produce a small strain. E is thus a measure of the elastic stiffness of a material.

However, when the extension (deformation) of the wire is too large, beyond proportional limit, solid will no longer obey Hooke’s law i.e. E is no longer a constant.

As the stress further increases, beyond the elastic limit, the wire has a permanent extension that the wire is no longer elastic and it undergoes plastic deformation. The extension increases rapidly ...

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