Stefan Boltzmann LawStefan Boltzmann Law
The Stefan-Boltzmann law, also known as Stefan's law, states that the total energy radiated
per unit surface area of a black body per unit time (also known as the black-body irradiance or
emissive power), , is directly proportional to the fourth power of the black body's
thermodynamic temperature T.Heat Transfer Definition :-
Heat is the form of energy. We also know that there is a transfer
of heat only if there is a temperature difference. Heat Transfer is defined as:-
The transmission of energy from one region to another region
as a result of the temperature difference between them.
The Heat transfer taking place between the bodies of different temperature. Types of Heat transfer :- Know More About :- Oxidation and Reduction Math.Tutorvista.comPage No. :- 1/4
There are three modes of Heat transfer :- Conduction :-
Conduction is a process where the heat transfer takes place between the two
solid bodies in contact, two regions of the same solid body. This will happen because of the
hot, vibrating, and rapidly moving molecules transfer the heat to their neighboring atoms.Convection :-
The convection is a type of heat transfer where the heat transfer takes place
through a medium and the medium may be liquid or the gas. The heat transfer takes place by
the movement of fluid from one place to another. The heat transfer here is due to the bulk
motion of the fluid.
Convection is described by the Newton's law of cooling; the law states that the rate of heat
loosed by a body is proportional to the difference in temperatures between the body and its
The Third mode of energy transfer is Radiation Heat Transfer. The transfer of heat from hot
body to a cold body with any material medium for propagation.
Every object in the universe is made up of atoms and molecules. These atoms and molecules
vibrate due to thermal energy present in them.
Every object emits electromagnetic radiations because of the thermal vibrations of these
atoms and molecules.
In case of energy transfer, the radiation conversion of radiated electromagnetic energy to
thermal energy takes place. Radiation Heat Transfer can also be termed as transfer of energy
through waves.Learn More :- Dynamic Equilibrium Math.Tutorvista.comPage No. :- 2/4
Heat Transfer ExamplesExamples of Heat Transfer through Conduction: -
Take one long piece of metal. Put first
end of this metal in the flame. Gradually, you wil find that the temperature of the other end of
the metal in your hand starts increasing. Energy gets transferred from the first end under
flame to the second end of the metal in your hand by conduction.Examples of Heat Transfer through Natural Convection :-
Natural convection is the
convection which occurs natural y due to the bouncy effect. When water is heated in a pot
then the particles, atoms or molecules of the water which are in contact with the pot gain
energy. Kinetic energy of these particles gets increased.
As a result, density of these particles decreases and they start moving upward towards the
open surface of the port. Cool water which is in contact with the air in the port starts sinking
downward and convection current gets established.
Cool water in the upper surface is denser than the hot water in contact with the surface of the
pot. Convection Currents flow in circular fashion. Therefore, heat is transferred by the
movement of water (fluids).
Forced convection: The convection that takes place by the force that is the force created from
the fans, stirrers, pumps and etc.Examples of Heat Transfer through Radiation :-
Radiations coming out from the burner of
the electric stove or toaster coils. Transfer of heat energy from Sun to Earth or to us takes
place due to the electromagnetic rays emitted by the sun. Another example is the heating of
food inside the microwave. Math.Tutorvista.comPage No. :- 4/4