Question

The length of a wire changes by $0.04\%$ when the wire is subjected to a load. If $\sigma =0.5$ for the material of the wire, then the " change in diameter is:

• A. $0.2\%$
• B. $0.02\%$
• C. $0.002\%$
• D. $0.4\%$

Answer 1

The correct option is B $0.02\%$

$\sigma =\text{possion ratio}=\frac{\text{Relative Change in diameter}}{\text{Relative change in lingth}}=\frac{\frac{\Delta d}{d}}{\frac{\Delta l}{l}}$

$\frac{\Delta d}{d}=\frac{6\times \frac{\Delta l}{l}}{=}0.5\times 0.04\%$

$\frac{\Delta d}{d}=0.02\%$