Question

What happens to the resistance of a conductor whose area is doubled?

Answer 1

let the resistance of wire = r

resistivity of wire = R

area of cross - section = A

length of wire = l

resistance of wire , r = R×A/l                         -----(1)

when the area is doubled the new area is = 2A

let the resistance = r1 = R×2A/l                        -------(2)

divide eq. (2) by (1)

r/r1 = (R×A/l)/(R×2A/l)

r/r1 =  1/2

r1 = 2r

therefore , the resistance of wire became double