Understanding energy


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A guide on understanding the basics of energy

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Understanding energy

  1. 1. A guide
  2. 2. “There is a fact, or if you wish, a law, governing all natural phenomena thatare known to date.There is no known exception to this law—it is exact so far as we know. Thelaw is called the conservation of energy.It states that there is a certain quantity, which we call energy that does notchange in manifold changes which nature undergoes.That is a most abstract idea, because it is a mathematical principle; it saysthat there is a numerical quantity which does not change when somethinghappens.It is not a description of a mechanism, or anything concrete; it is just astrange fact that we can calculate some number and when we finishwatching nature go through her tricks and calculate the number again, it isthe same.” The Feynman Lectures on Physics
  3. 3.  What is energy? A brief history of energy Types of energy Measurement of energy Uses of energy Summary
  4. 4. “Energy is the capacity of a physical system to perform work. Energyexists in several forms such as heat, kinetic or mechanicalenergy, light, potential energy, electrical, or other forms.According to the law of conservation of energy, the total energy of asystem remains constant, though energy may transform into anotherform. Two billiard balls colliding, for example, may come to rest, withthe resulting energy becoming sound and perhaps a bit of heat at thepoint of collision.” The SI unit of energy is the joule (J) or newton-meter (N * m). The joule is also the SI unit of work.” About.com
  5. 5. “The word energy derives from the Greek ἐνέργεια energeia, which possibly appears for the first time in the work ofAristotle in the 4th century BCE. Thomas Young - the first to use the term "energy" in the modern sense.The concept of energy emerged out of the idea of vis viva (living force), which Gottfried Leibniz defined as theproduct of the mass of an object and its velocity squared; he believed that total vis viva was conserved.To account for slowing due to friction, Leibniz theorized that thermal energy consisted of the random motion of theconstituent parts of matter, a view shared by Isaac Newton, although it would be more than a century until this wasgenerally accepted. In 1807, Thomas Young was possibly the first to use the term "energy" instead of vis viva, in itsmodern sense.Gustave-Gaspard Coriolis described "kinetic energy" in 1829 in its modern sense, and in 1853, William Rankine coinedthe term "potential energy". It was argued for some years whether energy was a substance (the caloric) or merely aphysical quantity, such as momentum.William Thomson (Lord Kelvin) amalgamated all of these laws into the laws of thermodynamics, which aided in therapid development of explanations of chemical processes by Rudolf Clausius, Josiah Willard Gibbs, and WaltherNernst. It also led to a mathematical formulation of the concept of entropy by Clausius and to the introduction of lawsof radiant energy by Jožef Stefan.Since 1918 it has been known that the law of conservation of energy is the direct mathematical consequence of thetranslational symmetry of the quantity conjugate to energy, namely time. That is, energy is conserved because thelaws of physics do not distinguish between different instants of time (see Noethers theorem).” Wikipedia
  6. 6. There are several different types of energy and these are the main ones that should be understood:1. Mechanical: “the energy that is possessed by an object due to its motion or due to its position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position). Objects have mechanical energy if they are in motion and/or if they are at some position relative to a zero potential energy position (for example, a brick held at a vertical position above the ground or zero height position). A moving car possesses mechanical energy due to its motion (kinetic energy)." Physics Classroom2. Electric: “ the presence and flow of an electric charge. The energy portion of electricity is found in a variety of phenomena such as static electricity, electromagnetic fields and lightning. Humans have found the ability to harness these phenomena and store the electrical charge for later use. The concept of electrical energy is defined using a variety of different terminologies such as charge, current and potential” Wisegeek3. Thermal: “A specialized term that refers to the part of the internal energy of a system which is the total present kinetic energy resulting from the random movements of atoms and molecules.” Thermal Energy.org
  7. 7. Because energy is defined via work, the SI unit for energy is the same as the unit of work – the joule (J), named inhonour of James Prescott Joule and his experiments on the mechanical equivalent of heat. In slightly morefundamental terms, 1 joule is equal to 1 newton-metre and, in terms of SI base units:An energy unit that is used in atomic physics, particle physics and high energy physics is the electronvolt (eV).One eV is equivalent to 1.60217653×10−19 J. In spectroscopy the unit cm−1 = 0.000123986 eV is used to representenergy since energy is inversely proportional to wavelength from the equation E = hν = hc / λ.In discussions of energy production and consumption, the units barrel of oil equivalent and ton of oil equivalent areoften used. Unit ConversionGcal (109) MBtu (106) GJ (109) MWh (106) toe tce10 39.6832 41.8680 11.6300 1 1.42860.2520 1 1.0551 0.2931 0.0252 0.03600.2388 0.9478 1 0.2778 0.0239 0.0341Source IEA/Unit ConverterWhen discussing amounts of energy released in explosions or bolide impact events, the TNT equivalent unit is oftenused. 1 ton of TNT equivalent is equal to 4.2 × 109 joules. Therefore, 1 kt TNT is 4.2 × 1012 joules, and 1 Mt TNT is 4.2 ×1015 joules.Note that torque, the "rotational force" or "angular force" which causes a change in rotational motion is typicallyexpressed in newton-metres. This is not a simple coincidence: a torque of 1 newton-metre applied on 1 radianrequires exactly 1 newton-metre = 1 joule of energy. Wikipedia
  8. 8. There are various energy suppliers who have different clientelewho they sell energy to for different uses.Energy can be used for: Mechanical work Heating (such as radiators and under floor heating) Heat extraction (such as air conditioning) Transportation Industrial power Residential power sourcing
  9. 9.  Energy is the capacity of a physical system to perform work There are various types of energy and different ways to measure it. Depending on what energy is needed for, it may be used differently
  10. 10.  Please click on linked sources for full articles and references  Wikipedia  Wise Geek  Physics classroom  About.com