Question

A copper and a steel wire of the same diameter are connected end to end. A deforming force $F$ is applied to this composite wire which causes a total elongation of $1cm$. The two wires will have then

• A. the same stress and strain
• B. the same stress but different strain
• C. the same strain but different stress
• D. different strains and stress

Answer 1

Answer: (B)

the same stress but different strain

$stress=\frac{F}{A}$
As each wire is of same diameter, hence the area of cross section is same for both the wires. As both the wires have the same force ($F$) and same area of cross-section therefore, stress is same for both the wires
As young's modulus, $Y=\frac{stress}{strain}orStrain=\frac{stress}{Y}$
As $Y$ is different for both the wires and stress is same for both the wires, therefore strains is different for both the wires.