Which statement best describes energy transfer during thermal conduction between two objects in contact?

Which statement best describes energy transfer during thermal conduction between two objects in contact?

• A. Faster particles collide with slower particles, transferring energy.
• B. Electric charges are transferred from one object to the other.
• C. Heat is transferred only via radiation.
• D. Energy is created at the contact point and spreads.

Answer: (A)

When two objects are in contact and at different temperatures, energy transfer by conduction happens through particle interactions: the faster, hotter particles collide with neighboring slower particles and transfer some of their kinetic energy. This exchange continues along the contact area, moving energy from the hotter object to the cooler one until they reach equilibrium. In metals, free electrons also carry energy rapidly and transfer it by colliding with atoms; in nonmetals, energy moves mainly through lattice vibrations (phonons) from one atom to the next. Other statements miss the essence of conduction. Transferring energy by electric charges describes electrical conduction, not thermal conduction. Heat transfer via radiation does not require contact at all, so it isn’t describing conduction. And energy isn’t created at the contact point; it is transferred from regions of higher temperature to regions of lower temperature, conserving energy.

When two objects are in contact and at different temperatures, energy transfer by conduction happens through particle interactions: the faster, hotter particles collide with neighboring slower particles and transfer some of their kinetic energy. This exchange continues along the contact area, moving energy from the hotter object to the cooler one until they reach equilibrium. In metals, free electrons also carry energy rapidly and transfer it by colliding with atoms; in nonmetals, energy moves mainly through lattice vibrations (phonons) from one atom to the next.

Other statements miss the essence of conduction. Transferring energy by electric charges describes electrical conduction, not thermal conduction. Heat transfer via radiation does not require contact at all, so it isn’t describing conduction. And energy isn’t created at the contact point; it is transferred from regions of higher temperature to regions of lower temperature, conserving energy.