Heat Conduction in Metals by Free Electrons

Steps:

• Heat one end of the copper rod, creating a temperature gradient.
• In metals like copper, free electrons carry heat due to their mobility.
• Hotter regions have electrons with higher kinetic energy.
• These energetic electrons diffuse from hot to cold end, transferring heat.

Why D is correct:

• In metallic conduction, free electrons move from hotter to cooler regions, as per the kinetic theory of heat transfer in solids.

Why the others are wrong:

• A: Molecules in solids vibrate but do not move translationally from end to end.
• B: Molecules do not migrate; heat transfer occurs via electron movement, not molecular.
• C: Electrons move from hot to cold, not the reverse, to equalize temperature.

Final answer: D