Wednesday, July 28, 2010

Energy, Work and Power


Energy can be defined as the capacity for doing work
.In physics we say that work is done on an object when you transfer energy to that object.

If one object transfers (gives) energy to a second object, then the first object does work on the second object.

Work can be generally defined as transfer of energy.

Work and energy are mutually connected and must be considered together as work is often defined in terms of energy and vice versa.In other words, Work shifts energy from one system to another.

The S.I. Unit of Work is the Joule(J).

In summary,

Energy is …

* a scalar quantity,
* abstract and cannot always be perceived,
* given meaning through calculation,
* a central concept in science.

Different forms of energy

Energy can exist in many different forms. All forms of energy are either kinetic or potential. The energy associated with motion is called kinetic energy. The energy associated with position is called potential energy. Potential energy is not "stored energy". Energy can be stored in motion just as well as it can be stored in position. Is kinetic energy "used up energy"?

You should be able to recognise the main types of energy. One way to remember the different types of energy is to learn this sentance where each capital and highlighted letter is the first letter in the name of a type of energy;

Most Kids Hate Learning GCSE Energy Names

Types of Energy

Magnetic - Energy in magnets and electromagnets.

Kinetic - The energy in moving objects. Also called movement energy.

Heat - Also called thermal energy.

Heat is the movement of molecules. It is the sum of the kinetic energy of an object's molecules. In many physics textbooks, they look at heat as some sort of substance and heat energy as something independent of kinetic energy. In our lessons, it is just one subset of kinetic energy.
Electrical energy

Light - Also called radiant energy.Light is the movement of waves and/or light particles (photons). It is usually formed when atoms gain so much kinetic energy from being heated that they give off radiation. This is often from electrons jumping orbits and emitting moving photons.
Nuclear energy

Gravitational potential - Stored energy in raised objects.

Chemical - Stored energy in fuels, foods and batteries.
Chemical energy is potential energy until the chemical reaction puts atoms and molecules in motion. Heat energy (KE) is often the result of a chemical reaction.
Light energy

Sound - Energy released by vibrating objects.

Electrical - Energy in moving or static electric charges.

Electrical energy is the movement of electrons. That is kinetic energy. The voltage in an electrical circuit is the potential energy that can start electrons moving. Electrical forces cause the movement to occur.
Chemical energy

Elastic potential - Stored energy in stretched or squashed objects.

Nuclear - Stored in the nuclei of atoms.

Certain elements have potential nuclear energy, such that there are internal forces pent up on their nucleus. When that potential energy is released, the result is kinetic energy in the form of rapidly moving particles, heat and radiation.

(The most commonly applied forms of energy will be discussed.)


* kinetic energy — motion
o mechanical energy — motion of macroscopic systems
+ machines
+ wind energy
+ wave energy
+ sound (sonic, acoustic) energy
o thermal energy-- motion of particles of matter
+ geothermal energy
o electrical energy — motion of charges
+ household current
+ lightning
o electromagnetic radiation — disturbance of electric and magnetic fields (classical physics) or the motion of photons (quantum physics)
+ radio, microwaves, infrared, light, ultraviolet, x-rays, gamma rays
+ solar energy
* potential energy — position
o gravitational potential energy
+ roller coaster
+ waterwheel
+ hydroelectric power
o electromagnetic potential energy
+ electric potential energy
+ magnetic potential energy
+ chemical potential energy
+ elastic potential energy
o strong nuclear potential energy
+ nuclear power
+ nuclear weapons
o weak nuclear potential energy
+ radioactive decay
Another scheme (economic)

* solar
o sunshine
o wind
o ocean currents
o ocean thermal temperature gradients
o biomass
+ food
+ wood/charcoal
+ dung
o fossil fuels
+ coal
+ petroleum
+ natural gas
* everything else
o geothermal
o tidal
o nuclear


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