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 R_{A} and R_{B} are in the ratio

- 1 : 2
- 2 : 1
- 1 : 4
- 1 : 8

**Answer**

Resistance of wire is directly proportional to the length and inversely proportional to the cross-sectional area (square of radius).

L_{B} = 2 L_{A}

r_{A} = 2 rB which means r^{2}_{A} = 4 r^{2}_{B}

R_{A} = L_{A}/r^{2}_{A} = 1/8 R_{B}

**The correct option is D.**