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.
The sources of energy, which are used directly from nature, is known as primary sources of energy.
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:
The natural sources that are used in their primary form i.e. without any conversion are called primary sources of energy. For example wood, coal, natural gases etc.
|Renewable source||Non-renewable source|
|They are somewhat found abundantly.||They are found in limited quantity.|
|They can be replenished within a human life.||They take millions of years to form.|
|They are continuously formed in nature||They are not produced continuously by nature.|
Those resources that can be reused after it is used once are called renewable resources.
Coal is nonrenewable source of energy because it cannot be used more than once. Once used its existance is lost from this world. So it cannot be replaced.
The sources of energy, which are not produced continuously in nature and are exhaustible are called non-renewable sources of energy. Example: coal, petrol,etc.
The four renewable source of energy are:
Which one of the following is the factor that doesnot affect the pressure exerted by a liquid?
Value of acceleration due to gravity
Density of the liquid
volume of the liquid
Depth or height of the liquid column
The capacity of doing work is ______.
The type of energy possessed by a simple pendulum, when it is at the mean position is ______.