Two conducting wires A and B are made of same material. If the length of B is twice that of A and the radius of circular cross-section of A is twice that of B, then their resistances RA and RB are in the ratio
Resistance of wire is directly proportional to the length and inversely proportional to the cross-sectional area (square of radius).
LB = 2 LA
rA = 2 rB which means r2A = 4 r2B
RA = LA/r2A = 1/8 RB
The correct option is D.