Technical Aspects of Energy

  Energy is the  capacity  to  do  work - to  exert a force 'F' 
  through a distance 'd'; to  accelerate a mass 'm' from  rest 
  to some  velocity 'v'; to move an electric charge 'q' across 
  a voltage  difference 'V';  to lift a mass 'm' to height 'h'. 
  In  each  case, a specific  amount of energy  - Fd, (1/2)mv2,
  qV or mgh- is required. Energy comes in many different forms: 

  Potential energy  -   objects,  because  of  their  position, 
                        capable of doing work on other objects 
                        are said to possess potential energy; 
  Kinetic energy    -   the energy of moving body,proportional 
                        to its mass and the square of its speed; 
  Heat energy       -   the  kinetic  energy of random thermal 
                        motion of matter on an atomic scale; 
  Mechanical energy -   the kinetic energy of organised motion 
                        of bulk matter; 
  Electrical energy -   the  energy  due  to the  forces  that 
                        charged bodies exert on one another; 
  Chemical energy   -   the energy of chemical  bonds, due  to 
                        electrical forces acting at the atomic 
                        level in accord with quantum mechanics; 
  Nuclear energy    -   the  energy of nuclear  binding due to 
                        nuclear forces; 
  Gravitational energy -the energy due to the force of gravita-
                        tional attraction-such as the potential 
                        energy that a body of water has because 
                        of its height above sea level; 
  Light energy      -   the  energy  of  visible,  ultraviolet, 
                        infrared, electromagnetic radiation, etc. 

  Energy  undergoes  transformations  from one form to another. 
  These transformations are governed by the laws of thermodyna-
  mics, which state:
  (i)   Energy is a conserved quantity- while it can move from 
        one  place  to  another, it  is  neither  created  nor 
        destroyed. That is, the total amount  of  energy  does 
        not change.
  (ii)  In energy transformations, energy  tends to pass  from 
        concentrated  forms  to  dilute forms. It  changes  in 
        such  a  way  that  the  amount of work  that  can  be 
        obtained from it decreases.
  The first law of  thermodynamics is  based on laws of motion 
  of  Isaac  Newton, whose work was  instrumental in providing 
  theoretical  view  of  the  universe, in which energy is the 
  central  concept  linking  the  whole   range  of   observed 
  phenomena. Einstein  later, through his theory of relativity 
  was  able  to  transcend  Newtonian  concept of the physical  
  universe, widening  the perception of the nature of physical 
  reality.  Einstein's  special  theory of relativity  equated 
  mass  and energy and expressed it as E= mc2, that is, energy 
  is  equal  to  the  square  of  velocity  of  light .  Joule, 
  electronvolt, kilocalories, kilowatt-hour  and kilogram mass 
  are the units commonly used in the different disciplines  of 
  electricity, atomic  physics, dietetics  and  engineering to 
  express  energy. All  these  units that can be  expressed in 
  terms of each  other, can also be  reduced to units  of mass. 
  For  example, 1 kilowatt-hour is 3.6 Giga joules, 859.8 kilo 
  calories,  2.247x1025 electronvolt or 4.007 x 10-11 kilogram 
  mass. This  highlights the  unifying power of the concept of 
  energy. 
  Accounting  of  energy, using  the first  law, allows one to 
  translate  energy  from   various   sources   into   thermal 
  equivalent  units  such as kcal, while energy measured using 
  units (such as MTOE: million tonnes of oil equivalent, MTCE: 
  million tonnes of coal equivalent)based on the second law of 
  thermodynamics  takes into account  efficiency of conversion, 
  as well as, differing efficiencies of combustion. 

  Usefulness and  transformability  of energy are explained in 
  terms of  "entropy" by Clausis. Energy at a high temperature 
  is obviously  more  useful, or transformable, than energy at 
  low  temperature. This  leads to the  definition of  'energy 
  efficiency'. Efficiency  is  defined as the amount of useful 
  energy  produced  by a  system as a proportion  of the total 
  energy  input. In  assessing  the  resources as alternatives, 
  limitations  imposed  by  the  second law need to be clearly 
  appreciated.