Air Conditioning Repair Certification (ETI) 2025 – 400 Free Practice Questions to Pass the Exam

Heat transfer via contact is effectively described by conduction. This method involves the direct transfer of thermal energy between particles of matter that are in contact with each other. When two objects at different temperatures touch, heat will flow from the hotter object to the cooler one until thermal equilibrium is reached. This occurs because the faster-moving particles of the warmer object collide with the slower-moving particles of the cooler object, transferring energy through these collisions.

In contrast, convection refers to heat transfer through fluids (liquids or gases) due to the movement of the fluid itself. Radiation involves the transfer of heat through electromagnetic waves and does not require a medium or contact. Advection is a term often associated with the bulk movement of fluid, usually involving heat transport as a result of the fluid's flow but is not strictly about direct contact. The distinction is important because each method describes different mechanisms of heat transfer, with conduction being the primary mode when discussing heat transfer via direct contact between materials.