Two wires, P and Q, have equal resistance. Wire Q is made from a material whose resistivity is twice that of the material used for wire P. The diameter of wire Q is twice that of wire P. Find the ratio $\dfrac{\text{length of wire P}}{\text{length of wire Q}}$?
- A$\dfrac{1}{8}$
- B$\dfrac{1}{4}$
- C$\dfrac{1}{2}$
- D$\dfrac{2}{1}$