Transmission of Heat

Heats are transferred from one region to another in three ways. They
are conduction, convection, and radiation.

♦ Conduction

When one end of a metal rod is heated, the unheated end soon becomes
warm. This is because heat travels through the metal by the process of

All electrons are constantly vibrating and in metals the electrons are
mobile. When a metal is heated the kinetic energy of its electrons is
increased and they begin to move more rapidly and to move towards
the cooler parts of the metal. Hence their energy is transferred to the
cooler molecule.

♦ Convection

In the process of convection heat is carried by and transferred by the
movement of a liquid of gas. When liquid is heated at the bottom of a
container a current of hot liquid moves upwards to be replaced by a
current of cold liquid moving down.

♦ Radiation

Radiation is the way in which heat travels from the sun across space to
the earth’s atmosphere. This “radiant energy” consists of invisible
electromagnetic waves, which are partly reflected and partly absorbed.
It comes from the sun directly or indirectly and when coming directly
travels through 150 million km of space.
Conduction and convection are methods of heat transfer which both
require a medium but radiation is a method of heat transfer, which
requires no medium.
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