|
|
||
|
Heat - Part V |
||
|
|
||
|
Sources
of heat
:
Some of the important source of heat are discussed below. The sun
: For plant and animal life on earth, sun is the single most
important source of energy. Most of the sunís energy is in the form of
light and heat. In the sun tremendous amounts of hydrogen atoms are
undergoing nuclear fusion to form helium atoms. The hydrogen atoms are brought
close to each other for fusion because of the enormous amounts of
gravitational force. The mass of helium atom formed is less than the masses
of two hydrogen atoms fused. The missing mass appears as energy, given by
Einsteinís equation E = mc2. Helium nuclei again fuse to form
higher elements. This again releases energy. The large amounts of heat thus
generated makes the sunís temperature very high ( ~ 107C)
The energy from the sun is released by electromagnetic waves or photons. The
photons travel through space and reach the earth in 8 minutes from the time
they are released. These are energetic photons. The average energy of the
photons is a few electron volts[1]. The electrical
energy :
In all electrical appliances used in the house, the electrical energy is
converted into heat. This is done through joules law P = IV. (More
information on this) Each
appliance contains a coil which has high resistance to the flow of
electricity. When current is
passed through the appliances such as heater, toaster, water geyser, oven,
etc. the resistor is taking the energy from the flowing electrons and is
becoming hot. The heat is then dissipated to the surrounding. In a toaster
you can see the resistance makes the elements of the toaster glow red. Chemical energy
: A large quantity of heat may
be generated by burning chemicals such as petrol, kerosene, oil, wood, etc.
The chemicals in these substances burn with the help of oxygen in the air.
The chemical energy stored thus gets converted into heat energy. The food we
eat also keeps the body warm. The chemical energy stored in the fats,
proteins and carbohydrates that we eat, keeps our body functional and warm. Nuclear Energy
: Nuclear energy is released either by nuclear fusion or by
nuclear fission. In nuclear fusion, the atoms fuse together. The resultant
atom will always have mass less than the fused atom. The missing mass is
given out as nuclear energy. Similarly, in nuclear fission, large atoms like
Uranium are unstable. They break up when slightly disturbed, into smaller
atoms. Again it is seen that the sum of the resultant atoms is less than the
original Uranium atom. The missing mass comes out as energy [1] An electron volt is another unit for measuring energy. It is the energy needed for taking a charge of 1 electron through 1 volt. 1eV is a much smaller unit than 1 joule.
|
||
|
||
|
|
