Question

Two wires of smae material are having lengths in the ratio 2:3 and radii 1:2 find the ratio of their resistances

Answer 1

R is directly promotion to length and indirectly proportional to area. So

R1=l1/a1

R2=l2/a2

If l1/l2=2/3 then l1=2/3 l2

And a1/a2=(1/2)^2 ( a=πr^2) so a1=a2/4

R1=2/3 l2 / (a2 /4)

L2/a2=r2 solve to get ratio