申論題

13. The figure shows a wire that changes in width. However, we don't know if the wire narrows as in the first drawing or widens as in the second drawing. The drift speed in region 1 at the left is 8.00 × m/s. The resistivity is 1.69 × ohm-m. The density of conduction electrons is 8.49 × 1028 m³. In both sections, the current is uniformly distributed over the cross section. In region 2 on the right, in length L = 1.00 cm, the potential change AV = 1.80 × V. What is the ratio of radii r₁/r₂?