[" Example "3.18" A wire has a resistance "R." Find new resistance,"],[" (i) if radius of cross-section of a cylindrical wire is doubled,then "R],[" find ratio of initial to final resistance."],[" (iii) if length of wire is increased by "10%," then find the percentage "],[" increase in its resistance."],[" (iii) if length of wire is increased by "20%," then find the percentage "],[" increase in its resistance."],[qquad [" If "],[qquad (1)/(1)]]