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her is an Answer that'll get you FULL 4 marks
ELASTIC ;
Elastic Deformation : when a copper is stretched
upto elastic limit and then the stretching force is
removed , the material
will regain it's Original Shape and Size .
Elastic Region : Stress is
Directly Proportional to Strain
PLASTIC ;
Plastic Deformation : When the Copper wire is stretched
Beyond Elastic limit and if the force is
removed , the material will have
Permanent extensionPlastic Region : Stress is
NOT Directly Proportional to Strain