Question

For a material $\sigma =-0.25$ under an external stress, the longitudinal strain is ${10}^{-2}$. The percentage change in the diameter of the wire is

• A. $+1$%
• B. $-1$%
• C. $+0.25$%
• D. $-0.25$%

Answer 1

Answer: (C)

$+0.25$%

$=\frac{\Delta d}{d}\times 100$

$=-\sigma \frac{\Delta l}{l}\times 100$

$=-(-0.25)\times 10^{-2}\times 100$

$=+0.25$%
(Negative sign is there because increase in length causes decrease in diameter)