Energy
The greek word energeia means something like activity, operation. Energy is involved in each and every process, change and movement. It comes in different forms of energy which can transformed into each other.
Energy comes in various forms:
- A falling stone has the energy of movement (kinetic energy).
- Electric currents have electrical energy.
- A battery has chemical energy.
- A wound spring has elastical energy.
- The sun has light energy (radiation energy).
- Objects placed in different heights have different elevation energy (potential energy).
- Hot objects have heat energy (thermal energy).
In every process imaginable, energy transforms its form to varying degrees:
- When a car brakes, kinetic energy is transformed into thermal energy.
- When coal is burned in a coal power plant, chemical energy is transformed into thermal energy and then into kinetic energy. The resulting kinetic energy is then in part transformed into electrical energy.
When a bouncy ball falls, its elevation energy transforms into kinetic energy. In the moment of its hitting the ground, the elevation energy is completely transformed. At the same time, the kinetic energy transforms into elastical energie. The ball expands again and its elastical energy transforms back into kinetic energy. While moving upwards, this kinetic energy transforms to elevation energy again.
It is fundamental that energy is never lost. No matter what happens, no part of the energy is ever wasted. This rule is called the law of energy conservation. The movement of the bouncy ball comes to an end because a part of its energy transformed into heat energy.
Energy is measured in the unit Joule [J].
- When you go 20 kilometers per hour on your bicycle, your kinetic energy is at about 20,000 J
- If you take a look at the printings on grocery packages, you will find how much energy is stored in your food. 100g of sugar, for example, has a chemical energy of 1,700kJ, that is 1,700,000 J. (k means kilo, which equals 1000)
- A usual 1.5V battery, however, can only store about 13,500J.
