What is wind power?

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”.

When was coal formed?

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.

 


Which is the main source of energy for the earth?

The sun is the biggest source of energy for the earth. The energy that actually reaches the earth is about 400,000,000,000,0000 kilowatt hours per day. Its energy is converted into food by the green plants. Now-a-days, solar energy is being used in solar cookers-heating systems, solar furnaces, lighting and producing electricity.

 


What is silicon used for?

Silicon only occurs naturally in combination with other elements. It is found in rocks as silicates. Silica or silicon-dioxide is found in sand and other minerals. The chief use of silicon is in making chips containing microcircuits for computers and other electronic equipments.

 


How do we classify natural resources?

They are classified as: inexhaustible, renewable and non-renewable. Inexhaustible resources are those which are not likely to be exhausted by man's consumption such as air, sand and clay. Renewable resources are naturally replenished after man's consumption such as water, wood, pastures etc. The resources which cannot be replaced after use such as fossil fuels, metals etc. are called non-renewable resources. 

From which sources are the basic needs of man met?

Plants and animals are the main sources of food for man. Plants provide us with cereals, vegetables, fruits and edible oils. Animals give us meat. Rivers, wells, springs ponds, rains, etc., are the main sources of water. Plants and animals’ hair are the main sources of clothes. Modern science has provided us with synthetic fibres like nylon, terelene, etc.

 


Why did dinosaurs vanish?

 It still remains a scientific puzzle. One opinion is that the earth's climate grew cooler and the forest dwindled. With the loss of their habitats they died out. Another answer may lie in outer space. Had the earth been hit by a commet or huge meteorite there would have been great explosion. Dust rising into the atmosphere would have blotted out the sun’s warmth. The plants on which the dinosaurs fed would have died out and so would they. 

What is bio-luminescence?

The production of light by living beings is called bio-luminescence. Some bacteria and fungi, glow worms, several fishes produce light of various colours. Animal luminescence is involved in communication, camouflage, or the luring of prey.