Exhaustible sources of energy means non-renewable sources of energy. Coal and petroleum are the two exhaustible sources of energy (or non-renewable sources of energy). This is due to the following reasons : Coal and petroleum are fossil fuels which were formed in the earth very, very slowly. The coal and petroleum which are present in the earth today have taken millions of years to form and get accumulated. So, if all the coal and petroleum present in earth get exhausted, they cannot be produced quickly in nature. We will not get any coal or petroleum in the near future.
