Topic: Intro to Current. Two cylindrical copper wires have the same length but different diameters. Wire A has diameter $d_A$ and Wire B has diameter $d_B$, with $d_B>d_A$. If the same potential difference $V$ is applied across each wire, which wire can carry the higher current?

• A. Both carry the same current because the material is copper in both cases.
• B. Wire B, because its larger cross-sectional area gives a smaller resistance $R=\frac{\rho L}{A}$ and thus a larger current $I=\frac{V}{R}$.
• C. Neither; current depends only on length $L$, not on diameter.
• D. Wire A, because a smaller diameter increases the electric field and therefore increases current.

Answer: (B)