1.+About+Energy

=Energy=
 * [[image:http://www.treehugger.com/mitsubishi-i-miev-electric-car-rrr01.jpg width="272" height="179"]] || [[image:energy_tree.jpg width="366" height="146" align="center"]] ||

**Definition of Energy ** Energy is the capacity or the ability to do work.

Energy can either be
"active" energy is energy that is //doing// something. "stored" energy is energy that //could do// something ("potential" energy)

Scientists have observed that:
"//Energy can neither be destroyed nor created, but can only be transformed from one form to another//."

Energy can never be converted into useful work with 100% efficiency.
'Useful energy' refers to the energy that ends up as useful work. What is lost as heat is called 'waste' energy. Consider the way energy is used and lost in a typical food chain:  

**Energy Sources**
Energy can be stored in many ways. When energy is stored it is **potential** energy and can be used as a source of energy with which we can do work. e.g. A battery stores chemical potential energy which can be converted into active electrical energy doing work like powering an iPod.

Energy is measured in //joules//.
1,000 joules (J) = 1 kilojoule (kJ) 1,000,000 joules (J) = 1 megajoule (MJ)

**Power**
Power is the rate energy is used so is measured in joules per second (J/s) which are also called //watts//. 1,000 watts (W) = 1 kilowatt (kW) 1,000,000 watts (W) = 1 megawatt (MW) 

[[image:scientist_girl.jpg width="179" height="179" caption="scientist_girl.jpg"]]

 * ==== energy is not a substance ====
 * ==== energy has different forms ====
 * ==== energy can be changed from one form to another ====
 * ==== energy can only be detected when a change occurs ====
 * ==== energy can be actively doing work or stored ====