Q.
The dimensions of four wires of the same material are given below. In which wire the increase in length will be maximum when the same tension is applied?
As , Y=LlAF=πr2×lF×L l=πr2×YF×L
For given F and Y,l∝r2L∝D2L ∴l1:l2:l3:l4=D12L1:D22L2:D32L3:D42L4 D12L1=(1mmm)2100cm,D22L2=(2mmm)22000cm,D32L3=(3mmm)2300cm,D42L4=(0.5mmm)250cm
So, l1:l2:l3:l4=1:21:31:2
Clearly l4 is maximum. So correct option is (d) ..