Heat conduction in metals via free electrons

Steps:

• Heat transfer in the rod is conduction, the main mode in solids.
• Copper, a metal, conducts heat primarily through free electrons, not molecules.
• At the hot end, electrons gain kinetic energy from increased temperature.
• These energetic electrons diffuse to the cooler end, transferring heat.

Why D is correct:

• Kinetic theory states that in metals, free electrons carry thermal energy from hotter to cooler regions via random motion and collisions.

Why the others are wrong:

• A: Molecules in solids vibrate but do not translate between ends; conduction is via electrons.
• B: Same as A; molecular movement does not occur in this way.
• C: Electrons move from hot to cold, not the reverse, to equalize temperature.

Final answer: D