Learning physics and chemistry easily and freely - Science for elementary school, middle school and high school

Free online mechanics lesson for elementary school,  middle school and high school.



Energy basics

1) What is energy ?

The concept of energy is linked to various situations but it can be defined as follows:
An object owns energy if it can acts on itself or on another object.

In this definition " to act " means there can be modifications of:
- shape
- trajectory
- speed
- position
- température
- pressure
- chemical composition
- electrical state
- magnetical state

2) Main types of energy

main forms of energy are:
- Kynetic energy (motion energy)
- Potential energy ( position energy )
- Chemical energy 
The light energy 
- Electrical energy
- heat energy

3) Transfers and energy conversions

When an object gives a part of its energy to another object there is an energy transfer.
When energy changes its form, there is an energy conversion.
Lorsque l'énergie d'un corps est transmise à d'autres corps on parle alors de transfert d'énergie.

Lorsque l'énergie d'un corps change de forme on parle alors de conversion d'énergie.

Talking about chemical transformations, the french chemist Lavoisier established a simple rule:
" Nothing is lost, nothing is created, everything is transformed "
This rule also applies for energy:
- If an object's energy decreases it isn't lost: this energy is transfered to another object or converted in another type of energy.
- If an object's energy increases it is not created from nothing: this energy comes from another object, or results from an energy conversion.
To sum up, every energy change can be explained by a transfer or a conversion.

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