Q78 / 160 · JIPMER 2014 · Physics
A steel wire of 1 m long and $1 \mathrm{~mm}^2$ cross section area is hanged from rigid end when weight of 1 kg is hanged from it, then change in length will be
(Young's coefficient for wire $Y=2 \times 10^{11} \mathrm{~N} / \mathrm{m}^2$)
- A$0.5$ mm
- B$0.25$ mm
- Correct answerC$0.05$ mm
- D$5$ mm
Solution
Young's coefficient of elasticity
$Y=\frac{m g L}{\pi r^2 \Delta L}$
Substituting the values, we get
$\Delta L=0.05 \mathrm{~mm}$
Hence, the correct answer is option: 'C'.