Below a certain depth all the porous spaces are saturated with water. This upper limit of the ground water is called the water table.
Water cycle or hydrological cycle is the natural evaluations of water through biosphere. Water is lost from earth’s surface to the atmosphere by evaporation from rivers, oceans, and seas etc. This atmospheric water forms clouds and creates rainfall. The water that collects on land, again flows to oceans, seas and rivers etc., and completes the cycle.
Rain, snow, rivers, streams, brooks, lakes, ponds, wells, springs, underground water, ice sheets, etc. are the main sources of water.
Pure water is colourless, odourless and tasteless. It can exist as solid (ice), liquid (water) and gas (steam). Water freezes at 0°C or 32° F and boils at 100°C or 212°F. It is a peculiar liquid in that it expands when it freezes. That is why ice floats on water.
Water makes up 60-70% of the human body or about 40 liters of which 25 are inside the cells, 15 outside. People can't survive normally more than five or six days without water or two or three days in a hot environment.
To scientists, water is a compound of hydrogen and oxygen. One molecule of water contains two atoms of hydrogen and one atom of oxygen. There is about 1.4 billion Cubic kilometer of water on the earth which covers about 71% of the earth's surface. About 97% of the water on the earth is in the oceans.
Most parts of India, except Rajasthan, receive an average annual rainfall of about 110 cm which generates about 2.75 million cubic km of water per year.
Nuclear fusion is the process whereby two atomic nuclei are fused with the release of a large amount of energy. Very high temperatures and pressures are thought to be required in order for the process to happen. The process might one day be harnessed to form the basis of commercial energy. Method of achieving controlled fusion is the subject of research around the world.
Nuclear power is obtained from the energy stored in the nuclei of atoms. Nuclear power is produced by splitting the atoms of some element like uranium. The uranium nuclei are split by the bombardment of neutrons. This is called nuclear fission. Energy produced by nuclear fission has been harnessed since 1950s. When a nucleus splits it gives large amount of energy. This energy is used to heat up water and convert it into steam. The steam runs a turbine which in turn produces electricity. Nuclear power is generated with the help of nuclear reactors. However, the use of nuclear energy has given rise to concern over safety.
The world’s largest solar plant is located in the MOJAVE desert neat Dagget, California. It currently producing 675 MW of electricity, enough energy for one million people.
Solar energy absorbed by the earth is equivalent to 3000 times the heat in all the coal and petroleum produced in the world in a year.
Mechanical or electrical power is generated by a wind mill using wine energy. Wind mills are of two types: horizontal axis type and vertical axis type. In both the types, blades are rotated by the kinetic energy of wind. Netherland is called “The Land of Windmills”.
Gasoline, kerosene, diesel, lubricants, greases, wax, asphalt, etc. are the different petroleum derivatives. These are obtained by the fractional distillation of crude oil.
Coal was formed about 250,000,000 years ago. Formation of coal began when plant debris accumulated in swamps, partially decomposing and forming “peat layers”. A rise in the sea level or land subsidence buried these layers below weight-compressed marine sediments, whose weight, compressed the peat transforming it under high-temperature conditions to coal. The greater the pressure, the harder the coal.