Conduction, convection, and radiation are three different ways in which heat can be transferred from one object to another. Here are the key differences between them:

Conduction

• Heat transfer occurs between objects by direct contact.
• It is the transfer of thermal energy through direct molecular collision.
• Conduction is the most common form of heat transfer and occurs via physical contact.
• Examples of conduction include placing your hand against a window or placing metal into an open flame.
• Conduction is a longer process than convection or radiation because it needs molecules to come into contact with one another.

Convection

• Heat transfer takes place within a fluid, such as air or a liquid.
• It occurs when a fluid is heated and then travels away from the source, carrying the thermal energy along.
• The fluid above a hot surface expands, becomes less dense, and rises, while the cooler fluid sinks.
• Convection currents are formed as the hot air rises and pushes denser, colder air down.
• Examples of convection include boiling water and heating a room with a radiator.

Radiation

• Heat transfer occurs through electromagnetic waves without involving particles.
• Thermal radiation generates from the emission of electromagnetic waves.
• Radiation is the heat transfer mechanism in which the transition takes place through electromagnetic waves.
• Examples of radiation include the heat from the sun and the heat emitted by a fire.

In summary, conduction transfers heat via direct molecular collision, convection transfers heat through the movement of a fluid, and radiation transfers heat through electromagnetic waves.