Introduction to Energy

Energy is the capacity of doing work. Whenever an object is capable of doing work, we understand it has some energy. We are capable of doing any kind of work only if we have some energy. In the same way, a machine can also perform any work if it has some energy.

A simple machine such as lever, pulley, inclined plane etc. uses our muscular energy to do work. However, if the machine is complicated they need some sources of energy such as coal, petroleum, electricity, etc.

All present sources of energy such as coal, diesel, petrol, hydroelectricity, solar energy, tidal energy, nuclear energy, geothermal energy are classified into primary energy sources and secondary energy sources.

Sources of energy:

Primary energy sources:

The sources of energy, which are used directly from nature, is known as primary sources of energy.

Secondary energy sources:

The sources of energy, which are derived from primary sources, are called secondary sources.

Based on replacing period, the sources of energy are classified as:

1. Non-renewable source of energy
   The sources of energy that is stored in nature from several million years and cannot be replaced if it is used once are called the non-renewable source of energy. Some examples are coal, petroleum, natural gas, nuclear energy, etc.
2. Renewable source of energy
   The sources of energy, which can never be exhausted and can be replaced quickly if it is used once is called the renewable source of energy. For example Hydropower or hydroelectricity, wind energy, solar energy, tidal energy, geothermal energy, etc.