Story Behind Discovering Energy

Today we all use the term energy. But did we ever stop to think when was this term introduced or what is the meaning of energy? The word energy is derived from the Greek word energeia. The term energy was first used by Thomas Young. The common symbol that is used for denoting energy is E. Joules is the SI unit of energy. Erg, kiloWatt hour, BTU, the foot-pound, and calories are the other units of energy.

The sun is believed to be the first source of energy that is ever known to mankind. The energy obtained from the sun was in the form of heat and light. The second source of energy is fire. The fire was discovered by striking two stones which generated heat and light. The fire was first discovered by the cavemen. After a few years, humans realized that energy can be obtained from the wind as well as water. Today we are familiar with them as wind energy and hydro energy. 

Common sources of energy

There are many different sources of energy and some of them are listed below:

Solar energy

This was the first source of energy from the sun and also a natural source. Solar energy is harvested by storing the energy in the solar panels which are then converted into electricity. Solar energy is renewable energy in which the heat and light from the sun is converted into electricity. These days people prefer solar energy as it is an abundant source. It is environment friendly, and it is easy to generate electricity using solar energy. 

Wind energy

Wind energy is obtained from the air that is moving around us. Wind energy is converted into electricity by installing wind turbines. The best part of these turbines is that they can work at sea as well as on land. The kinetic energy of the wind is converted to the motion of the blades which are further connected to the low-speed shaft. This low-speed shaft is connected to the small gears which connect the high-speed shaft. The high-speed shaft is connected to the generator which produces electricity. 

The advantage of wind energy is that it is environmentally friendly, renewable energy as well as sustainable energy. While the disadvantages of wind energy are that the fluctuation in the wind pattern can affect the overall efficiency of the plant. Also, it causes noise pollution.


Hydropower is also known as hydroelectricity which refers to the conversion of energy from the flowing water. The potential energy of the flowing water is converted into mechanical energy which runs the turbine for the production of electricity. In the 21st century, hydropower is the most widely used source of energy. It is renewable energy and eco-friendly. A typical hydropower plant consists of three parts and they are:

  • Place where the electricity produced
  • A dam which can be opened and closed so as to control the flow of water
  • A reservoir where the water is stored

To learn more about the types of energy and their applications, stay tuned with BYJU’S. Also, subscribe to our YouTube channel for more information. 

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