What is Energy?

  • (noun): (physics) the capacity of a physical system to do work; the units of energy are joules or ergs.
    Example: "Energy can take a wide variety of forms"
    See also — Additional definitions below

Energy

In physics, energy (Ancient Greek: ἐνέργεια energeia "activity, operation") is an indirectly observed quantity that is often understood as the ability of a physical system to do work on other physical systems. However, this must be understood as an overly simplified definition, as the laws of thermodynamics demonstrate that not all energy can perform work. Depending on the boundaries of the physical system in question, energy as understood in the above definition may sometimes be better described by concepts such as exergy, emergy and thermodynamic free energy. Therefore, in the words of Richard Feynman, "It is important to realize that in physics today, we have no knowledge what energy is. We do not have a picture that energy comes in little blobs of a definite amount." However, it is clear that energy is always an indispensable prerequisite for performing work, and the concept has great importance in natural science.

Read more about Energy.

Some articles on Energy:

Enthalpy - Applications
... Internal energy, U, must be supplied to remove particles from a surrounding in order to allow space for the creation of a system, providing that environmental variables, such as pressure (p ... This internal energy also includes the energy required for activation and the breaking of bonded compounds into gaseous species ... within enthalpy calculations as U + pV, to label the amount of energy or work required to "set aside space for" and "create" the system describing the work done by ...
Nuclear Power - Nuclear Decommissioning
... The price of energy inputs and the environmental costs of every nuclear power plant continue long after the facility has finished generating its last useful electricity ... The total energy required for decommissioning can be as much as 50% more than the energy needed for the original construction ...
Obesity
... by a combination of excessive food energy intake, lack of physical activity, and genetic susceptibility, although a few cases are caused primarily by genes, endocrine disorders, medications or ... yet gain weight due to a slow metabolism is limited on average obese people have a greater energy expenditure than their thin counterparts due to the energy required to maintain an ... Diet quality can be improved by reducing the consumption of energy-dense foods such as those high in fat and sugars, and by increasing the intake of dietary fiber ...
Enthalpy Versus Internal Energy
... The U term can be interpreted as the energy required to create the system, and the pV term as the energy that would be required to "make room" for the system if the pressure of the environment remained constant ... T, is created or brought to its present state from absolute zero, energy must be supplied equal to its internal energy U plus pV, where pV is the work done in pushing against the ambient (atmospheric) pressure ... of the system and therefore the internal energy is used ...
Transformations of Energy
... One form of energy can often be readily transformed into another with the help of a device- for instance, a battery, from chemical energy to electric energy a dam ... the case of a chemical explosion, chemical potential energy is transformed to kinetic energy and thermal energy in a very short time ... At its highest points the kinetic energy is zero and the gravitational potential energy is at maximum ...

More definitions of "Energy":

  • (noun): A healthy capacity for vigorous activity.
    Example: "Jogging works off my excess energy"
    Synonyms: vim, vitality
  • (noun): Enterprising or ambitious drive.
    Example: "Europeans often laugh at American energy"
    Synonyms: push, get-up-and-go
  • (noun): An imaginative lively style (especially style of writing).
    Example: "His writing conveys great energy"
    Synonyms: vigor, vigour, vim
  • (noun): An exertion of force.
    Example: "He plays tennis with great energy"
    Synonyms: vigor, vigour

Famous quotes containing the word energy:

    Children are intensely invested in getting their way. They will devote more emotional and intellectual energy to winning arguments than parents ever will, and are almost always better rested.
    Jean Callahan (20th century)

    Three elements go to make up an idea. The first is its intrinsic quality as a feeling. The second is the energy with which it affects other ideas, an energy which is infinite in the here-and-nowness of immediate sensation, finite and relative in the recency of the past. The third element is the tendency of an idea to bring along other ideas with it.
    Charles Sanders Peirce (1839–1914)

    Much of the modern resistance to chastity comes from men’s belief that they “own” their bodies—those vast and perilous estates, pulsating with the energy that made the worlds, in which they find themselves without their consent and from which they are ejected at the pleasure of Another!
    —C.S. (Clive Staples)