What is a key characteristic of conduction in heat transfer?

Conduction is a mode of heat transfer that is characterized by the transfer of thermal energy through direct contact between materials. This transfer occurs at the microscopic level as energetic particles in a material collide with their neighbors, passing on kinetic energy. For example, when one end of a metal rod is heated, the energy is transmitted along the rod as the particles at the heated end vibrate more vigorously and collide with adjacent, less energetic particles, transferring heat along the rod.

This characteristic distinguishes conduction from other modes of heat transfer like convection, which involves fluid movement, and radiation, which involves the transfer of energy through electromagnetic waves. While temperature differences can influence conduction, the fundamental principle is that direct contact is necessary for this type of heat transfer to occur.