Problem 3
A uniform wire of resistivity , length , and cross-sectional area is kept at constant temperature. It is slowly drawn into a wire of the same material and volume, length , with uniform new area and unchanged resistivity. (a) Find initial resistance. (b) Find new area and resistance. (c) Compare the resistances and explain why the area must change. Keep the sign convention consistent and use appropriate SI units throughout. Each part builds on intermediate results from the preceding part; apply a physical relation only where the stated model assumptions hold. Finally compare the answers with the initial conditions, expected trends, and an independent check when available.
problems.proof.stepOf
problems.proof.analysis
Collect answers to every part, including signs, directions, and image or process properties where relevant. Dimensions match the physical quantities.