Two wires $P$ and $Q$, both formed from the same material, are attached to the same electrical supply. $P$ is twice as long as $Q$ and has one-third of the diameter of $Q$, as shown in the diagram. Determine the ratio $\dfrac{\text{current in }P}{\text{current in }Q}$?
- A$\frac{2}{3}$
- B$\frac{2}{9}$
- C$\frac{1}{6}$
- D$\frac{1}{18}$