PHYSICS · Multi-part · CBSE · Physics · Current Electricity · Current Electricity
Problem
In a laboratory demonstration, four identical copper wires labeled P, Q, R, and S are immersed in separate oil baths whose temperatures are maintained at 20 °C, 40 °C, 60 °C, and 80 °C, respectively. Each wire has the same length and cross-sectional area and is connected to an identical 6.0 V dc power supply. No significant heating occurs from the current—the wires remain at the bath temperatures.
Answer the following questions about the relative electrical resistance of the four wires.
(a) Rank the wires from smallest to largest resistance. Clearly state any equality that exists.
(b) Describe, in terms of atomic-level interactions between charge carriers and the lattice, why the ranking you provided in part (a) is expected for copper.
(c) Suppose instead that the wires were made of a hypothetical material whose resistivity decreases linearly with temperature over the same range. Rank the resistances of wires P, Q, R, and S for this new material and explain your reasoning.