Related topics: power
Energy
hideIn physics, energy (from the Greek ἐνέργεια - energeia, "activity, operation", from ἐνεργός - energos, "active, working") is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law. Different forms of energy include kinetic, potential, thermal, gravitational, sound, light, elastic, and electromagnetic energy. The forms of energy are often named after a related force.
Any form of energy can be transformed into another form, but the total energy always remains the same. This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.
Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy relative to the Earth.
For more information about Energy, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with energy
Turning heat to electricity... efficiently
Nov 18, 2009 |
4.8 / 5 (62) |
9
(PhysOrg.com) -- In everything from computer processor chips to car engines to electric powerplants, the need to get rid of excess heat creates a major source of inefficiency. But new research points the way ...
Metal-Air Battery Could Store 11 Times More Energy than Lithium-Ion
Nov 05, 2009 |
4.4 / 5 (48) |
12
(PhysOrg.com) -- A spinoff company from Arizona State University plans to build a new battery with an energy density 11 times greater than that of lithium-ion batteries for just one-third the cost. With a ...
Ultracapacitors Make City Buses Cheaper, Greener
Oct 21, 2009 |
4.5 / 5 (45) |
31
(PhysOrg.com) -- A fleet of 17 buses near Shanghai has been running on ultracapacitors for the past three years, and today that technology is coming to the Washington, DC, for a one-day demonstration. Chinese ...
How a Solar-Hydrogen Economy Could Supply the World's Energy Needs
Aug 24, 2009 |
4.1 / 5 (48) |
67
(PhysOrg.com) -- As the world's oil supply continues to dry out every day, the question of what will replace oil and other fossil fuels is becoming more and more urgent. According to the World Coal Institute, ...
High-performance plasmas may make reliable, efficient fusion power a reality
Nov 02, 2009 |
4.7 / 5 (40) |
47
In the quest to produce nuclear fusion energy, researchers from the DIII-D National Fusion Facility have recently confirmed long-standing theoretical predictions that performance, efficiency and reliability ...
Is global warming unstoppable?
Nov 23, 2009 |
3.5 / 5 (49) |
70
In a provocative new study, a University of Utah scientist argues that rising carbon dioxide emissions - the major cause of global warming - cannot be stabilized unless the world's economy collapses or society builds the ...
Second Law of Thermodynamics May Explain Economic Evolution
Nov 02, 2009 |
4.3 / 5 (34) |
29
(PhysOrg.com) -- Terms such as the "invisible hand," laissez-faire policy, and free-market principles suggest that economic growth and decline in capitalist societies seem to be somehow self-regulated. Now, ...
A Theory of Dark Matter
Sep 08, 2009 |
3.6 / 5 (41) |
58
Among the most astounding, unexpected, and important achievements of the past century (or even more) have been the discoveries of dark matter and dark energy, collectively dubbed the "dark sector."
Particles are back in the LHC
Oct 26, 2009 |
4.6 / 5 (30) |
2
During the last weekend (23-25 October) particles have once again entered the LHC after the one-year break that followed the incident of September 2008.
Lower-cost solar cells to be printed like newspaper, painted on rooftops
Nanotechnology / Nanomaterials
Aug 24, 2009 |
4.2 / 5 (32) |
12
Solar cells could soon be produced more cheaply using nanoparticle "inks" that allow them to be printed like newspaper or painted onto the sides of buildings or rooftops to absorb electricity-producing sunlight.
Solar power generation around the clock
Nov 05, 2009 |
4.6 / 5 (29) |
15
(PhysOrg.com) -- A Californian company, SolarReserve, is developing a solar power system that can store seven hours' worth of solar energy by focusing mirrors onto millions of gallons of molten salt, allowing ...
Researchers create smaller and more efficient nuclear battery
Oct 07, 2009 |
4.8 / 5 (27) |
14
(PhysOrg.com) -- Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are ...
Researchers Hope to Mass-Produce Tiny Robots
Aug 28, 2009 |
4.8 / 5 (26) |
31
(PhysOrg.com) -- Tiny robots the size of a flea could one day be mass-produced, churned out in swarms and programmed for a variety of applications, such as surveillance, micromanufacturing, medicine, cleaning, ...
Renewable Energy Made by Mixing Salt and Fresh Water
Sep 02, 2009 |
4.3 / 5 (27) |
6
(PhysOrg.com) -- When a river flows into the sea, the location is more than just a haven for water commerce. The mixing of fresh and salt water that occurs at an estuary also dissipates energy, as the different ...
Could Exotic Matter Provide an Infinite Source of Energy?
Sep 15, 2009 |
3.3 / 5 (34) |
63
(PhysOrg.com) -- Generally, scientists prefer to avoid the concept of perpetual motion. The idea of a machine that could produce movement that goes on forever, and using that movement to generate an endless ...
