When we think about energy the first thing that should spring to mind is the conservation of energy law. The law states that energy cannot be created or destroyed. This law is fundamentally important in physics.                                                                          

Instead of creating energy (which violates the law) we can move it from one form to another. There are seven forms of energy and these are:

·         Light energy

·         Kinetic (movement) energy

·         Sound energy

·         Heat energy

·         Potential (gravitational and strain) energy

·         Electrical energy

·         Chemical energy

Each of these are interchangeable. For example when you jump off a cliff at the top you have a lot of potential energy and then when you jump it will be converted into kinetic (movement) energy.  Some of the energy will be ‘lost’ as heat due to a force known as friction.                                                                                                                                              We can draw diagrams to show the conversion of energy. For example in a typical bedside light the energy will be converted like this: 

 Knowing that energy cannot be created or destroyed is really helpful in physics. Because of this we can say that if energy is fully converted between each that they are equal. For example in the diagram above if we had 5 joules[i] of electrical energy the light and heat energy combined must equal 5 joules[ii].                                                                                           

Later in this book you will be able to use this law to do long calculations by saying that one form of energy is equal to another.