SCIENCE CAPSULES

         Plants do photosynthesis using sunlight and yield us vegetables, fruits and grains.  Humans and animals eat this produce and get energy.      Sun's  heat causes rain and wind.  We derive electrical energy using wind mill.  We generate electricity using fast flowing water.        The plants and the animals that were buried deep inside the earth millions of years ago, have turned into coal and oil due to pressure and heat.  They are the best sources of energy even today.       Today we directly derive electrical energy from solar power and it is one of the best renewable energy .  A solar powered plane has already circumvented the earth.        No wonder that our ancestors had worshiped sun as a god. 

     Physics says, when a force is applied on an object and it moves to certain distance, work is said to be done.  The capacity for doing work is energy.      A body at a height, can fall down due to gravitational force . So it said to posses 'potential energy'.        A fast moving body can hit another body and do some work.  So it has 'kinetic energy'.      Petrol can burn, produce heat, gases expand,  pushes the piston of an engine and does some work.  Hence petrol has 'chemical energy' (heat energy)      The chemical in the battery reacts and push the electrons from one electrode to another making electric current.  So the battery stores 'chemical energy'.      When light falls on certain materials, it ejects electrons.  So even light has energy