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Energy is a word with more than one meaning.
- Mostly it is used in science to describe how much potential a physical system has to change. In physics, energy is a property of matter and space, objects and fields. It can be transferred between objects and can also be converted in form. It cannot, however, be created or destroyed.
- It may also be used in economics to describe the harnessing and sale of energy itself, as in fuel or electric power distribution.
- In ordinary language, the word is used to describe someone acting or speaking in a lively and vigorous way.
In science, energy is the capacity to do work; the maximum amount of change that can be made to a system.
Basic forms of energy include:
- Kinetic energy - energy which is in moving objects.
- Potential energy - stored energy.
- Heat - thermal energy
- Electrical energy
Conservation of EnergyEdit
Energy is a property that is not created or destroyed, although energy can change in form. This is a rule that is commonly understood as the "conservation law of energy". In respects to this rule, the total amount of energy that exists within an isolated system will always be the same, no matter what changes have been made to it.
In the early 20th century, scientist were able to discover that matter itself can be created from energy and vice versa. This is just another change of form. After these discoveries, the conservation law of energy was extended to become the conservation law of matter and energy: matter and energy can neither be created from nothing nor destroyed to the point of complete erasure from reality. Albert Einstein was the first to mathematically derive this in the formula E = mc2.
A stone is thrown upwards and falls to the ground.
- human throws the stone: energy store in muscles = chemical energy
- stone moves upwards = kinetic energy
- stone at the highest point = potential energy
- stone falls to ground = kinetic energy
- stone hits ground = thermal energy/sonic energy
Types of energyEdit
Scientists have identified many types of energy, and found that they can be changed from one kind into another. For example:
- Light energy
- Sound energy
- Renewable energy
- Solar energy
- Nuclear energy
- Elastic energy
- Gravitational potential energy
- Kinetic energy
- Dark energy
- Hamiltonian mechanics
- Internal energy
As in other kinds of measurements, there are measurement units. The units of measurement for measuring energy are used to make the numbers meaningful.
The SI unit for both energy and work is the joule (J). It is named after James Prescott Joule. 1 joule is equal to 1 newton-metre. In terms of SI base units, 1 J is equal to 1 kg m2 s−2. It is most often used in science, though particle physics often uses the electronvolt.