UNIT 2 What is Energy?

UNIT 2

WHAT IS ENERGY?

In the language of science energy is the ability to do work. There are various forms of energy, such as heat, mechanical, electrical, atomic and so on.

Energy is needed for all our activities. Energy is needed to make anything happen. It makes the sun shine, it makes cars and buses move, it even keeps you alive!

However, energy is very hard to explain. We know we have to 'save it' if we want to keep our bills down. We know that the glucose in a Mars bar is 'for energy'. If somebody is very active, we might say that he is 'energetic'. But exactly what is energy? Where does it come from?

We can store energy in different forms. It is then released and used. Food, oil, petrol, gas and electric batteries all produce useful energy.

Our largest energy source is the Sun. It supplies us with free energy. But we can't use solar energy for many of our activities, e.g. eating, driving, flying or communicating by radio or television. We have to use energy from other sources, such as fossil fuels. This costs money.

Energy is always changing from one form to another. So the chemical energy in food changes in our bodies to heat. This enables us to do work. If we climb stairs, the chemical energy changes to potential energy. If we run, the chemical energy changes to kinetic energy.

The total amount of energy remains the same. Energy is neither created nor destroyed. This is called conservation of energy.

However, when energy changes from one form to another, some of the energy is wasted. So the amount of useful energy is always less after a change.

Finally, our present sources of energy are limited. We must use less energy. We also need to find ways of using alternative energy sources.