1) Electricity is a form of energy. Electricity is the flow of electrons. All matter is made up of atbins , and an atom has a center, called a nucleus. The nucleus contains positively charged particles called protons and uncharged particles called neutrons. The nucleus of an atom is surrounded by negatively charged particles called electrons. The negative charge of an electron is equal to the positive charge of a proton, and the number of electrons in an atom is usually equal to the number of protons. When the balancing force between protons and electrons is upset by an outside force, an atom may gain or lose an electron. When electrons are “lost” from an atom, the free movement of these electrons constitutes an electric current.Electricity is a basic part of nature and it is one of our most widely used forms of energy. We get electricity, which is a secondary energy source, from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources as hydropower, geothermal power, wind power which are called primary sources. Many cities and towns were built alongside waterfalls ( a primary source of mechanical energy ) that turned water wheels to perform work. Before electricity generation began slightly over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves. Beginning with Benjamin Franklin’s experiment with a kite one stormy night in Philadeelphia, the principles of electricity gradually became understood. In the mid-1800s, Thomas Edison changed everyone’s life -- he perfected his invention – the electric light bulb. Prior to 1879, electricity had been used in arc lights for outdoor lighting. Edison’s invention used electricity to bring indoor lighting to our homes.2) A circuit breaker (CB) is an automatically operated electrical switch, which is designed to protect an electrical circuit from damage caused by oyerload or short circuit. Unlike a fuse, which has to be replaced when it blows, a circuit breaker can be reset, then switched on after the fault in the circuit has been cleared. Circuit breakers have current ratings from a few amperes to thousands of amperes. Notice that the breaker has a toggle, which can be used manually, like a switch. The difference is that an internal mechanism can also open the switch if the current is too high. Miniature circuit breakers (most common type for 240V circuits) are classified by the method used to cause the the mechanism to trip open. The methods are: thermal, magnetic, thermal-magnetic, electronic. There are many different technologies used in circuit breakers and they do not always fall into distinct categories. The following types are common in domestic, commercial and light industrial applications for low voltage (less than 1000V) use.
3) The electricity produced by a generator travels along cables to a transformer, which changes electricity from low voltage to high voltage. Electricity can be moved long distances more efficiently using high voltage. Transmission lines are used to carry the electricity to a substation. Substations have transfomers that change the high voltage electricity into lower voltage electricity. From the substation, distribution lines carry the electricity to homes, offices and factories, which require low voltage electricity.
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