A copper wire of cross sectional asrea 0.01 cm is under a tension of 20 N. Find the decrease in the cross sectional area. Young modulus of copper `=1.1xx10^11Nm^-2` and Poisson ratio 0.32.

Options

A. `1.28xx10^(-6) cm^(2)`
B. `1.6xx10^(-6) cm^(2)`
C. `2.56xx10^(-6) cm^(2)`
D. `0.64xx10^(-6) cm^(2)`

Answer

A

Explanation

`F = (Y A Delta l)/(l), sigma = ((-Delta r)/(r))/((Delta l)/(l)), (Delta A)/(A) = 2(Delta r)/(r)`