Potential drop varies inversely with cross-sectional area in series wires

Steps:

• Current I is constant through all wires in series.
• Electric field E = I ρ / A, so potential gradient dV/dx = -E is steeper for smaller A.
• In thicker wires (larger A), potential drops slowly over distance.
• Graph shows piecewise linear V(x) with slopes inversely proportional to A in each segment.

Why A is correct:

• Depicts steeper negative slope in thinner wire sections, matching ΔV = I (ρ L / A) for each wire.

Why the others are wrong:

• B: Uniform slope ignores varying areas and resistances.
• C: Potential rises overall, violating direction from high to low V.
• D: Nonlinear or reversed slopes contradict linear drop per Ohm's law.

Final answer: A