Energy

The capacity of a body to do work is called the energy of the body. The SI unit of energy is joule (J). Energy can exist in various forms. Different forms of energy are:

1. Mechanical energy: Energy by the virtue of which a body can do some mechanical work directly, is called mechanical energy. The common forms of the mechanical energy are:

• Kinetic energy:The energy possessed by a body due to its motion is called kinetic energy. Kinetic energy (K. E) of a body having mass m, and velocity v, is equal to equation That is, K. E = ^mv2

• Potential energy:The energy possessed by a body due to its position or configuration is called potential energy. Potential energy (P.E) of a body is P.E = m x g x h

Where, m is a mass of the body, g is the acceleration due to gravity and h is height.

2. Electrical energy: A form of energy created by the movement of electrons is called electrical energy. I.e. hydropower, generator, etc.

3. Light energy: Light is also form of energy that makes things visible. We use light in the different process like lightening the houses, running industries, etc. Plants use energy to make food.

4. Heat energy: Heat energy is obtained by burning combustible substances like coal, gas, kerosene, firewood, etc. We use heat energy to keep warm and to cook food.

5. Sound energy: Sound energy is also a form of energy which is produced by vibrations. We hear the sound when the vibrations travel through the air around it to vibrate.

6. Chemical energy: The energy stored in the matter such as the energy stored in food and fuels, is chemical energy.

7. Nuclear energy: The neutrons and protons exert an attractive force on each other when present in the nucleus. The energy associated with them is called nuclear energy.

8. Magnetic energy: The energy can also be produced by a magnet. A magnet is the source of energy. Electricity can be produced with the help of the magnet. It is more powerful and also can be used to lift a heavy weight.

Transformation of energy

Conversion of energy from one form to another form is called the transformation of energy.

When a candle burns, chemical energychangesinto light and heat energy. When a fan is switched on, it converts an electrical energy into mechanical energy. Similarly, when a lamp glows, it changes electrical energy into light and heat energy. These examples show that one type of energy can be changed into another type.

Examples:

1. A steam engine changes heat energy into mechanical energy.
2. Solar car converts solar energy into mechanical energy.
3. A microphone converts sound energy into electrical energy.

Conservation of energy

Energy can neither be created nor be destroyed but can only be changed from one form to other. This is called the principle of conservation of energy.