For wires of the the same material are stretched by the same load. The dimensions are given below, which of them will elongate most ?

Options

A. length 100 cm, diameter 1 mm
B. length 200 cm, diameter 2 mm
C. length 300 cm, diameter 3 mm
D. length 400 cm, diameter 0.5 mm

Answer

D

Explanation

`Y=(F)/(pi r^(2//4)) xx (L)/(Delta l)=Delta prop (L)/(r^(2))`
Hence `L//r^(2)` is maximum when `L=400` cm and D = 0.5 mm as compared to other cases.