Which heating modality is heating through direct contact with a hot medium?

• A. Conduction
• B. Convection
• C. Radiation
• D. Conversion

Answer: (A)

Direct contact heat transfer is conduction. When a hot object touches something cooler, energy moves from the hotter material to the cooler one through molecular interactions at the interface. The rate depends on how hot the object is, how well the two materials conduct heat (their thermal conductivities), how much surface touches, and how well the contact is made.

Convection involves heat transfer through the movement of a fluid (air or liquid) carrying energy as it flows, so you’d see heat spreading because the fluid itself is moving. Radiation transfers heat through electromagnetic waves and can happen without any contact at all. Conversion isn’t a primary heat-transfer mechanism here; it usually refers to energy changing form, like electrical energy turning into heat.