Energy
Understanding Energy
Rakesh Mohan Hallen
ENERGY is often confusing. While we often come across phrases like "Save Energy"; "Energy Crisis", "Energetic Person", in physics texts energy is said to be conserved. Students often ask: If energy is conserved, why is there an energy crisis?
One needs to delve into the etymology of the word energy to get a satisfactory answer. The word energy has its roots in the Latin word ergo which meant work, with the addition of the prefix en- it leads to another word energia which meant activity. So energy from very ancient times has been associated with activity and work. But what we mean by the term has also simultaneously undergone changes. Initially it was only associated with motion, then with the developments in technologies and science during past few centuries heat , light and chemicals also became associated. The word "energy" in the above phrases, then, refers only to the resources available to do activities. These resources as we all know are depleting and need to be conserved by our conscious efforts. What, then is the energy which is conserved naturally?
The word "energy" used by the physicist today has a different connotation. In most contemporary texts and those of past several decades it is defined as "the capacity or ability to do work', which can be in several different forms, and is conserved, i.e. it can neither be created nor destroyed". Work, in physics, is said to be done when a mass is moved under the influence of a force. A small stone with zillions of atoms vibrating within it has energy according to this definition. But, as we all know, this energy cannot be used in the sense electricity, or a piece of coal can be used. Thus the definition of energy in physics does not refer to resources available for doing useful work alone.
The Energy Concept
The definition of energy mentioned above leads to several questions from youngsters:
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