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Define Energy ?

I know, all the school books say energy is the ability to do work. But what does that

mean? Well it sort of means the ability to make something happen (the nearly-well-

known Dave Watson definition). Everytime a force is exerted on something through

a distance (which is the definition of work) something had to move, which meanssomething happened. But is that the definition of Energy? My thermo books say

work is a process of energy transfer. Not a single one of my numerous

thermodynamics text books says energy is "the ability to do work"

For the purpose of explaining energy to beginners, I think the best description is

the following nearly-well-known Dave Watson definition:

Energy is a property or characteristic (or trait or aspect?) of matter that makes

things happen, or, in the case of stored or potential energy, has the "potential" to

make things happen.

Without energy, nothing would ever change, nothing would ever happen. You might

say energy is the ultimate agent of change, the mother of all change agents.

Knowing how to define chemical energy requires both an understanding of the basic

concepts of energy as well as the specific characteristics of chemical energy. We are all

dependent on many types of energy to accomplish the tasks of the day, and most of them

are based on chemical energy. A quick examination of what chemical energy is and how it is

used is thus helpful in giving us a better understanding of its many uses.

Energy is the ability to do work. It is measured in Joules.

TYPES OF ENERGY

Potential Energy is stored energy. There are 3 types of potential energy - Chemical potential energy (in

food, batteries and dynamite), Elastic potential energy (in rubber bands and springs), and Gravitational

potential energy (of objects some height above the ground)

Kinetic Energy is the energy of moving objects.

Light or Radiant Energy

Heat or Thermal Energy

Sound Energy

Electrical EnergyNuclear Energy

kinetic energy

Kinetic energy is the energy of motion, observable as the movement of an object, particle, or set of particles. Any object in motion is using kinetic energy: a person walking, a thrown baseball, a crumbfalling from a table, and a charged particle in an electric field are all examples of kinetic energy at work.

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Objects that are not in motion possess potential energy (the other main type of energy), which isconverted to kinetic energy when some force , such as gravity , acts upon the object to set it in motion.Elastic potential energy, for example, is stored in a stretched rubber band; when the rubber band isreleased, the stored energy is converted to kinetic energy.

Definition: Potential energy, or stored energy, is the ability of a system to do work due to its positionor internal structure. For example, gravitational potential energy is a stored energy determined by anobject's position in a gravitational field while elastic potential energy is the energy stored in a spring.

Radiant EnergyThe radiant energy from the sun is the source of both light and heat energy to photosynthesis. Light energy isharvested by the pigments in order to carry out the breaking down of water molecule into hydrogen and oxygen. Thisis an energy-intensive process. Sunlight can be split into seven different colours which is called the spectrum.

Definition: Heat energy (or just heat ) is a form of energy which transfers among particles in asubstance (or system) by means of kinetic energy of those particle. In other words, under kinetictheory, the heat is transfered by particles bouncing into each other.

Sound energy is energy produced by sound vibrations. Sound vibrations cause waves of pressure. These waves lead to some level of compression and refraction through which the

waves travel. So, sound energy is a form of mechanical energy. Sound energy is energyproduced by sound vibrations. Sound vibrations cause waves of pressure. These waves lead tosome level of compression and refraction through which the waves travel. So, sound energy is aform of mechanical energy.

Electrical energy or Electromagnetic energy is a form of energy present in any electric

field or magnetic field, or in any volume containing electromagnetic radiation. The SI unit of electrical

energy is the joule, while the unit used by electrical utility companies is thewatt-hour  (Wh) or the kilowatt-

hour (kWh.)

Electrical energy is related to the position of an electric charge in an electric field. The electrical energy of 

a charge Q situated at theelectric potential V equals to the product QV . If V  is a potential difference, the

same expression gives the energy transformed when the charge moves through the potential difference.

A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a

steady rate (as opposed to a nuclear explosion, where the chain reaction occurs in a split second).

Currently all commercial nuclear reactors are based on nuclear fission. For experiments on reactors

based on nuclear fusion, see fusion power .

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nuclear 

reactor  

Electrical energy

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sound

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Light

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