How heat is transmitted?

* Conduction is the transfer of heat energy between two objects in physical contact. For example, when you touch a hot stove, heat from the stove is transferred to your hand through conduction. The rate of heat conduction depends on the temperature difference between the objects, the area of contact, and the material of the objects.

* Convection is the transfer of heat energy by the movement of a fluid. For example, when you boil water, heat from the bottom of the pot is transferred to the water through convection. The heated water rises to the top of the pot and is replaced by cooler water from the bottom. This process continues until all of the water is heated. The rate of heat convection depends on the temperature difference between the fluid and the surrounding environment, the density of the fluid, and the speed of the fluid flow.

* Radiation is the transfer of heat energy through electromagnetic waves. For example, heat from the sun is transferred to the Earth through radiation. The rate of heat radiation depends on the temperature of the object, the emissivity of the object, and the distance between the object and the surrounding environment.

In most real-world situations, heat is transferred by a combination of conduction, convection, and radiation. For example, when you turn on a space heater, heat from the heater is transferred to the air by convection and radiation. The heated air then transfers heat to the objects in the room by conduction.