Energy: The Property of Objects, Unit of Energy, Forms of Energy (For CBSE, ICSE, IAS, NET, NRA 2022)

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Energy: The Property of Objects

Definition of Energy “Energy is the Ability to Do Work”

  • Physical or chemical resources are processed to generate energy which is further used to provide light or heat for domestic or industrial purposes.
  • Different types of energy which can never be created nor destroyed.
  • Energy can only be transformed from one form to another.

Unit of Energy

  • The SI unit of energy is Joules (J) which is nothing but a term for Newton-meter.
  • When a certain amount of force (Newton) is applied to an object and it moved a certain distance (meters) , then the energy applied is said to be Joules (newton-meters) .

Forms of Energy

Forms of Energy
  • There are two types of energy:
    • Kinetic energy (working)
    • Potential energy (static)
  • There are two forms of energy sources:
    • Renewable source of energy
    • Non-renewable source of energy

Following are the examples of types of energy based on their sources:

  • Renewable source:
    • Solar energy
    • Wind energy
    • Geothermal energy
  • Non-renewable source:
    • Natural gas
    • Coal
    • Petroleum products

Types of Energy

Types of Energy
  • There are different forms of energy but the distinction between them is not always clear.
  • As Richard Feynman, a famous physicist once said, “The notions of potential and kinetic energy depend on a notion of length scale.”
  • As an Example, one can speak of macroscopic potential and kinetic energy, which do not include thermal potential and kinetic energy.
  • Also, what is called chemical potential energy is a macroscopic notion, and closer examination shows that it is really the sum of the potential and kinetic energy on the atomic and subatomic scale.
  • Same remarks apply to nuclear “potential” energy and most other forms of energy.

Kinetic Energy

The energy in motion is known as Kinetic Energy. For example, a moving ball, flowing water, etc.


m = Mass of the object

v = Velocity of the object

Potential Energy

This is the energy stored in an object and is measured by the amount of work done. For example, a pen on a table, water in a lake, etc.


  • m = Mass of the object (in kilograms)
  • g = Acceleration due to gravity
  • h = Height in meters

Mechanical Energy

It is the sum of potential energy and kinetic energy that is the energy associated with the motion & position of an object is known as Mechanical energy. Thus, we can derive the formula of mechanical energy as –

Solar Energy

  • The light and heat from the sun, harnessed using technologies like, solar heating, photovoltaic՚s, solar thermal energy, solar architecture, and artificial photosynthesis is known as solar energy.
  • It is the prime source of renewable energy.

Wind Energy

  • It is one of the various forms of energy. The energy present in the flow of wind, used by wind turbines is called wind energy. This energy is a major cheap source to produce electricity.
  • In these phenomena, the kinetic energy of the wind is converted into mechanical power.

Nuclear Energy

  • The energy present in the nucleus of an atom is known as nuclear energy.
  • The particles of an atom are tiny and need the energy to hold themselves.
  • Nuclear energy is that enormous energy in the bonds of an atom which helps to hold the atom together.
  • It can be used to make electricity.

Geothermal Energy

  • The energy or heat present inside the Earth is known as geothermal energy.
  • It is a cheap & convenient heat and power resource and use of this energy don՚t have a side effect like greenhouse gas emission etc.

Tidal Energy

Tidal energy or tidal power is a form of hydropower (energy present in water) , which converts the energy present in the tides to produce electricity.

Biomass Energy

Biomass is organic matter obtained from living organisms. The energy produced from biomass is called biomass energy.

Electrical Energy

The energy caused by moving electric charges is known as electrical energy. Electric energy is a type of kinetic energy as the electrical charges moves.

Thermal Energy

  • As the name suggests, thermal energy is the energy obtained from heat. It is a microscopic, disordered equivalent of mechanical energy.
  • There may be instances where an object posses more than one type of energy. For example, boiling water, posses both kinetic and potential energy along with heat energy.

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