Question

The stress-strain plot for wires made of two materials (I and II) is presented schematically in the accompanying figure. The points $C_I$ and $C_{II}$ represent fracture points of the two materials I and II respectively. It can be concluded from these graphs that

• A. material I has Young's modulus larger than that of material II
• B. the linear region of material I extends to a larger value of stress than that of material II.
• C. both materials I and II are equally brittle.
• D. material I is more ductile than material II.

Answer 1

The correct option is D material I is more ductile than material II.

We start checking each option:-

$\left(A\right)$:- Since slope of straight line that is proportional part is greater for material-$II$ , hence the ratio $\frac{stress}{strain}$ and thus Young's Modulus is greater for material $II$.

$\left(B\right)$:- This is wrong as from graph it is clear that the linear region of material $I$ extends to lesser value of stress than that of material $II$.

$\left(C\right)$:- Both having different nature and different breaking stress and hence are not equally brittle. Material $I$ having lesser breaking stress is more brittle than material $II$.

$\left(D\right)$:- Since for same stress, material $I$ undergoes more deformation than material $II$, hence it is more ductile.

Hence, only option (D) is correct.