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Sources of Energy

Good source of energy

We are familiar with the term energy. Everyday, we hear about the scarcity of energy and a looming crisis caused by the rapid depletion of energy reserves. Energy can be neither created nor destroyed. Hence, it should be conserved.

Energy is the ability or the capacity of a physical system to do work.

Are there different forms of energy? Can each form of energy be changed into another form?

Yes, energy exists in various forms such as kinetic energy, heat energy, chemical energy, etc. We can change energy from one form to another. For example, when a candle is burned, it produces heat and light. Here, we can see that the chemical energy in the candle is converted to light and heat energy.


Thus, we can say that a candle is a source of both light and heat. On the other hand, burning of coal produces heat. Does it also produce light?

What makes some forms of energy good while others bad?

Let us answer the question using light and coal as examples. Which of the two will you use as a source of heat energy to cook food? 

You will use coal as a source of heat energy to cook food. But, why coal and not candle? After all, both sources of energy produce heat. 

This is because the heat from the candle is not sufficient to cook.

This implies that specific sources of energy are used for specific purposes, which we refer to as good sources of energy for that particular task.

Good sources of energy exhibit some special characteristics that are listed below.

  • It should possess a high calorific value, i.e., the amount of energy obtained by burning one kilogram of the fuel should be high
  • It should not leave residue after burning, i.e., it should burn completely
  • It should burn without producing too many pollutants
  • It should be easily available and accessible
  • It should be economical
  • It should be easy to store and transport

Coming back to our earlier discussion,

When we compare coal and candle as sources of heat energy, we find that both are easily available, economical, and easy to store. However, coal is more efficient than candle, i.e., coal has a higher calorific value. One kilogram of coal will provide more energy as compared to one kilogram of candle-wax. Therefore, we prefer coal to candle when we require heat energy.

Let us further understand some characteristics of a good fuel.

In addition to a high calorific value, a good fuel must also have a fairly low ignition temperature. What will happen if the ignition temperature of a substance is lower than the normal room temperature? 

The fuel will be very difficult to store and transport. Any thermal contact with the atmosphere will ignite the fuel and it may result in an explosion.

Calorific value is defined as the amount of heat energy obtained by burning one gram of a substance. The unit of calorific value is kJ/g.

The ignition temperature of a substance is defined as the temper...

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