A topper wire of cross-sectional area 0.01 cm is under tension of 20 N. Find the decrease in the cross-sectional area Young modulus of copper = 1.1 × 1011 N m-2 and Poisson ratio = 0.32.


1.164 × 10-6 cm2

Given, cross-sectional area,


Tension in the wire,


Young modulus of the wire,


We know, stress,


And strain is given by ,


Young’s modulus then becomes,


therefore, longitudinal strain becomes,


Let the circular cross-section be of diameter


Given, Poisson’s ratio


hence, lateral strain


We know, area is given by






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