1. Introduction

Electricity means all the phenomena that result from the interaction of electrical charges. Electric and magnetic effects are caused by the relative positions and movements of charged particles of matter. When a charge is stationary (static), it produces electrostatic forces on charged objects, and when it is in motion it produces additional magnetic effects. So far as electrical effects are concerned, objects can be electrically neutral, positively charged, or negatively charged. Positively charged particles, such as the protons that are found in the nucleus of atoms, repel one another. Negatively charged particles, such as the electrons that are found in the outer parts of atoms, also repel one another (see Atom). Negative and positive particles, however, attract each other. This behavior may be summed up as: like charges repel, and unlike charges attract. [pic]

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Lightning Charges between clouds or between a cloud and the ground produce atmospheric electrical discharges—lightning. The flow of electricity from one discharge point to another also produces a sound wave heard as thunder.

2. Short History

Before the concept of electricity appeared people were aware of it by shocks from an electric fish called "Thunderer of the Nile". Similar reports appeared a few thousand years later, in the works of ancient Greek, Roman and Arabic naturalists and physicians. Arabs are thought to be the first ones to discover the identity of lightning, and electricity from any other source, as they had the Arabic word for lightning (raad) applied to the electric ray before the 15th century. In 1600 the English physician William Gilbert made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber.

He used the New Latin word electrics to refer to the property of attracting small objects after being rubbed and, in time, this association gave rise to the English words "electric" and "electricity". In the 18th century, Benjamin Franklin conducted extensive research in electricity and, in June 1752, his work paid off as he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky.A succession of sparks jumping from the key to the back of the hand showed that lightning was indeed electrical in nature.

From that point on things developed at a superior speed: in 1791 Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles; Alessandro Volta's battery, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used; Hans Christian Ørsted and André-Marie Ampère's research made it possible that concepts like electromagnetism, the unity of electric and magnetic phenomena to be officially recognized in 1819-1820 ; Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analyzed the electrical circuit in 1827.

Through such people as Nikola Tesla, Thomas Edison, Ottó Bláthy, Sir Charles Parsons, George Westinghouse, Ernst Werner von Siemens, Alexander Graham Bell and Lord Kelvin, electricity was turned from a scientific curiosity into an essential tool for modern life, becoming a driving force for the Second Industrial Revolution.

3. Definition

Electricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic induction.

4. Electricity sources

People have been trying to solve the electricity issue when faced with an acute shortage of electricity, so every country wants to increase power production in all possible ways. The most prolific source of electric energy are the nuclear power plants, but the risk of a catastrophic event, such as Chernobyl in 1986, makes people think twice before accepting this kind of energy source. Of course there are other ways of acquiring electrical energy, called alternative sources of energy. Wind energy, solar energy, sea waves energy are the latest resources, but the technology for them is still developing so they can be used only in a few countries. There are many reasons we are looking towards alternative energy sources. With many countries, and US cities, signing the Kyoto Treaty, efforts to reduce pollutants and greenhouse gases are a primary focus in today's culture.

Alternative, or renewable energy, sources show significant promise in helping to reduce the amount of toxins that are by-products of energy use. Not only do they protect against harmful by-products, but using alternative energy helps to preserve many of the natural resources that we currently use as sources of energy. To understand how alternative energy use can help preserve the delicate ecological balance of the planet, and help us conserve the non-renewable energy sources like fossil fuels, it is important to know what types of alternative energy is out there. - Wind Power

Wind energy harnesses the power of the wind to propel the blades of wind turbines. The rotation of turbine blades is converted into electrical current by means of an electrical generator. In the older windmills, wind energy was used to turn mechanical machinery to do physical work, like crushing grain or pumping water. Wind towers are usually built together on wind farms. Now, electrical currents are harnessed by large scale wind farms that are used by national electrical grids as well as small individual turbines used for providing electricity to isolated locations or individual homes. In 2005, worldwide capacity of wind-powered generators was 58,982 megawatts, their production making up less than 1 of world-wide electricity use.


* Wind power produces no pollution that can contaminate the environment, Since no chemical processes take place, like in the burning of fossil fuels, in wind power generation, there are no harmful by-products left over. * Since wind generation is a renewable source of energy, we will never run out of it. * Farming and grazing can still take place on land occupied by wind turbines which can help in the production of bio fuels. * Wind farms can be built off-shore.

* Wind power is intermittent. Consistent wind is needed for continuous power generation. If wind speed decreases, the turbine lingers and less electricity is generated. * Large wind farms can have a negative effect on the scenery. - Solar Power

Solar energy is used commonly for heating, cooking, the production of electricity, and even in the desalination of seawater. solar power works by trapping the sun's rays into solar cells where this sunlight is then converted into electricity. Additionally, solar power uses sunlight that hits solar thermal panels to convert sunlight to heat water or air. Other methods include using sunlight that hits parabolic mirrors to heat water (producing steam), or simply opening a rooms blinds or window shades to allow entering sunlight to passively heat a room.

Properties: * Solar power is a renewable resource. As long as the Sun exists, its energy will reach Earth. * Solar power generation releases no water or air pollution, because there is no chemical reaction from the combustion of fuels. * Solar energy can be used very efficiently for practical uses such as heating and lighting. * The benefits of solar power are seen frequently to heat pools, spas, and water tanks all over. * Solar power does not produce energy if the sun is not shining. Nighttime and cloudy days seriously limit the amount of energy produced. * Solar power stations can be very expensive to build.