Energy
Example: In a plant that furnishes pumped-storage hydroelectricity, mechanical work and electrical work is done by machines like electric pumps and electrical generators. The pumped water stores mechanical work. The amount of energy put into the system equals the amount of energy which comes out of the system, less that amount of energy used to overcome friction.
Such examples suggested the derivation of some unifying concepts: Instead of discerning (transferred) forms of work or stored work, there has been introduced one single physical quantity called energy. Energy is assumed to have substance-like qualities; energy can be apportioned and transferred. Energy cannot be created from nothing, or to be annihilated to nothing, thus energy becomes a conserved quantity, when properly balanced.
Describing the transfer of energy two dictions, two ways of wording are used:
(energy carriers exchanging energy) Physical interactions occur by carriers (linear momentum, electric charge, entropy) exchanging energy. For example, a generator transfers energy from angular momentum to electric charge.
(energy forms transforming energy) Energy forms are transformed; for example mechanical energy into electrical energy by a generator.
Often the energy value results from multiplying two related quantities: (a generalized) potential (relative velocity, voltage, temperature difference) times some substance-like quantity (linear momentum, electrical charge, entropy). — Thus energy has to be measured by first choosing a carrier/form. The measurement usually happens indirectly, by obtaining two values (potential and substance-like quantity) and by multiplying their values.
- (see any measurement device for energy below)
For the ranges of energy-values see: Orders of magnitude (energy)
Read more about this topic: Measuring Instrument
Famous quotes containing the word energy:
“There are no accidents, only nature throwing her weight around. Even the bomb merely releases energy that nature has put there. Nuclear war would be just a spark in the grandeur of space. Nor can radiation “alter” nature: she will absorb it all. After the bomb, nature will pick up the cards we have spilled, shuffle them, and begin her game again.”
—Camille Paglia (b. 1947)
“Violence among young people ... is an aspect of their desire to create. They don’t know how to use their energy creatively so they do the opposite and destroy.”
—Anthony Burgess (b. 1917)
“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)