∆l=F/A l/Y=4F/(πD²) l/Y
In Length = 50cm, diameter = 0.5mm, l/D² = 50/0.05² = 2×10⁴ cm^-1
In Length = 100cm, diameter = 1mm, l/D² = 100/0.1² = 10⁴ cm^-1
In Length = 200cm, diameter = 2mm, l/D² = 200/0.2² = 5×10³ cm^-1
In Length = 300cm, diameter = 3mm, l/D² = 300/0.3² = 3.3×10³ cm^-1
Hence ∆l is maximum in Length = 50cm, diameter = 0.5mm.