A copper wire and a steel wire of the same diameter and length are connected end to end and a force is applied which stretches their combined length by 1 cm. Then the two wires will have

Since the stress is defined as the relationship between force and cross-sectional area, and since there are two wires, one made of steel and the other of copper, the young's moduli of these materials will differ because the young's moduli depend on the materials, but because the diameter of the area of both wires, copper and steel, is the same, the cross-sectional area would be the same.

$\Delta l=\frac{F.l}{A.E}$

Because different materials never have the same young's modulus, the length change for both wires will be different. Wires will therefore experience the same stress but distinct strains.

Hence the correct answer is The same stress but different strain .