Energy

Energy is the ability or capacity to do work. The S.I unit of work done and energy is a joule (J).

Sources of energy:
The raw material for the production of energy is called the energy source.
There are two types of energy sources.

(a) Non-renewable sources of energy
These are energy sources, which cannot be replaced when they get used up.

Examples of non- renewable sources of energy
(i) Fossil fuels; these are formed from plant remains that died million years ago. They include; coal, petroleum oil, natural gas, e.t.c.
(ii) Nuclear fuels; these are fuels found in radioactive elements which may be occurring naturally such as Uranium.
These fuels can be used in nuclear reactions to produce electricity.

Advantages of non-renewable source of energy.
They have high energy density. I.e a lot of energy can be produced from a small quantity.
They are readily available as demand increases.

Disadvantages of non-renewable source of energy.
They are highly polluting.

(b) Renewable sources of energy
These are energy sources which can be replaced when they get used up. They can never get exhausted.
Advantage:
They are non-polluting.
Examples of renewable sources of energy.

(i) Solar energy: This is the form of energy which reaches the earth in form of heat and light.
It can be harvested using solar panels and transformed into electrical energy, which is used for many purposes.
It is also used in direct low temperature heating.
(ii) Wind: Wind can be harvested using giant windmills, which can turn electrical generators to produce electrical energy, which is a more useful form.
(iii) Running water: Running water is used in hydro- electricity plants to turn giant turbines, which produce electrical energy.
The water will always flow hence a renewable source. Tides can also be used to generate electricity in this way.
(iv) Geothermal energy: Water is pumped to hot under ground rocks where it’s heated and then forced out through another shaft where it can turbines.

Forms of energy

Energy can exist in the following forms;

a) Chemical energy:
Chemical energy is the form of energy a body has due to the nature of its atoms and molecules and the way they are arranged.
In the combination of atoms to form compounds, there is gain or loss of energy. This energy is stored in the compound as chemical energy.
If the atoms in such compounds are rearranged to form a new compound, this energy is released. E.g If sugars in the human body are burnt, a lot of chemical energy is released.

b) Nuclear energy:
This is the energy released when atomic nuclei disintegrate during nuclear reactions.
In nuclear reactions, the energy, which holds the nuclear particles together (Binding energy), is released.

There are two types of nuclear reactions i.e. fission (Where large nuclei break to form smaller ones) and fusion (Where smaller nuclei combine to form larger ones). In both cases, large amounts of energy are released.

c) Electrical energy (Electricity):
This is the form of energy which is due to electric charges moving from one point of a conductor to another.
This form of energy is most easily converted to other forms, making it the most useful form.

d) Light energy:
This is the form of energy which enables us to see. Light is part of a wider spectrum of energy called the electromagnetic spectrum. Light consists of seven visible colours, of red, orange, yellow, green, blue, indigo and violet. We are able to see because the eye is sensitive to the colours.

e) Heat energy:
Heat is a form of energy, which results from random movement of the molecules in the body.
It is responsible for changes in temperature.
When a body is heated or when heat energy of the body increases;

(i) The internal kinetic energy of the molecules increases leading to a rise in temperature.
(ii) The internal potential energy of molecules increases leading to expansion and change of state of the body.

f) Sound energy:
This is the energy which enables us to hear.
Like light, sound is also a form of wave motion, which makes particles to vibrate. Our ears are able to detect sound because it produces vibrations in the ear.

g) Mechanical energy:
This is the energy of motion.

Mechanical energy = kinetic energy + Potential energy

There are two forms of mechanical energy.
(i) Kinetic energy:- This is the energy possessed by a body due to its velocity or motion.

There are two forms of mechanical energy.
(i) Kinetic energy:- This is the energy possessed by a body due to its velocity or motion.

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(ii) Potential energy:– This is the energy possessed by a body due to its position or condition.
It is equal to the work done in putting the body in that position or condition.
A body above the earth’s surface has an amount of gravitational potential energy equal to the work done against gravity.
Weight is the force of gravity acting on a body.
Weight = mg.

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