What is energy

What is energy
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Energy is capacity to do work.

“The energy cannot be created or destroied, it can only be changed from one form to another.”

  • How? Why? Is it a magic?
  • No, it is a science. Read bellow and find the answers.
By definition, work is an energy requiring process. Work is a force applied to an object over a certain distance, such as pulling or pushing a wooden block across your desk. Your muscles do work when they facilitate body movement. Units of work and energy are joules

There are 2 main type of energy:

see more about energy types … >>>

And main forms of energy:


Energy measurement system

The international measurement system for energy is named “Système International d’Unités” (french abbreviation: SI). The international recognized unit for energy is the Joule (J), named after James Joule. He was the scientist who for the first time demonstrated the rule that work can be converted into heat.

Any form of energy can be transformed into another form. The process of energy transformation is also known as energy conversion.

Energy doesn’t disappear – just changes the forms.

Energy transformation is the process of changing energy from one form to another. This process is happening all the time.

Law of conservation of energy states that energy can change form, but it cannot be created or destroyed.
That means the total amount of energy stays the always the same.


Energy type is different than energy form.

All energy forms could be set as two type of energy – potential and kinetic energy.
Kinetic energy is the motion. Potential energy is the stored energy.


Chemical energy is a potential energy. That type of energy comes from the bonds of atoms and molecules.

An example for the stored (potential) energy is the mechanical energy.

For example the people utilize the chemical energy from the food they consume, and their body transforms it into mechanical energy, that allows them to run, play game, do work and etc.


Sound energy (energy of the sound) is a type of wave motion. When we talk we breathe out that occurs the effect of air motion which is because the air molecules vibrating. The vibrating molecules hit our eardrums. That allow us us to hear when we talk.
Sound energy is possible to be converted into electrical energy and to transmit from one place to another – good example for it is the radio, phone…. After that this electric energy could be transformed back to sound energy that we can hear.

Electrical energy
is the moving electrical charges from one point to another in a conductor.
Electrical energy also can be transformed into another form of energy. An example for that is the lightning.

Nuclear Energy (atomic energy) is the energy stored in the nucleus of an atom. Based on that energy the nucleus are hold together. That energy can be released when we combine (energy fusion) or split (energy fission) the nuclei.

Thermal energy (heat energy) is the total kinetic energy of atoms and molecules that are constantly in motion. Thermal energy causes faster moving that breaks bonds between molecules.


Radiant energy (light) is the energy of electromagnetic wave.

For example, energy of food could be transformed in energy to play. Chemical energy from coal, oil, natural gas can be transformed into heat energy (process of burning the fuel). The heat energy can be converted into kinetic energy by gas turbines or into electrical energy by generators.


Sun gives the grass thermal energy. The grass use it to grow up and transform it to a chemical energy using the photosyntesis proces. Rabbit eat the grass and use it as an energy source to grow up and to have power to run.

Hunting dogs like rabits, but they can run after them only if they have anough power to do that. To have power dogs need to be feed.

If you turn on the power switch the electricity bulb will use the electricity power and will transform in to light.





The example of transformation of chemical energy into mechanical energy is the car engine.

Other example is the wind turbine that you know. Turbine uses the wind energy and transform in to electricity.

Solar panels transform light to electricity.
Look around you and try to find other examples for energy transformation.

The energy transformation process is characterizing with so called “energy conversion efficiency.” This is the ability to transform energy form from one to another with the minimal losses. All known systems, vehicles, machines and etc have own and different coefficient of energy conversion efficiency.