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Electricity. Direct current and alternating current.

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Electrical energy is the most common form of energy because it is easy to obtain,

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it can be transported over long distances, and it can easily be transformed into many

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other forms of energy, like light, heat, sound and movement.

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Last year, you learned that all materials are made up of atoms, and, in turn, atoms are made

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up of other particles that are even smaller. We can classify these tiny particles according to

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their charge into three types, protons, positive charge, electrons, negative charge, and neutrons,

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uncharged particles. Generally, atoms are neutral. This is because they have the same

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number of protons as electrons, so their electrical charge is balanced.

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When the charge becomes unbalanced, the bodies become electrically charged,

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either with a negative charge, if there are more electrons than protons, or with a positive charge,

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if there are more protons than electrons. This creates forces between the atoms,

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and these forces tend either to draw the atoms together or to repel them,

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depending on their electrical charge. As a result, voltage is generated.

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Electric current, flow of electrons from one atom to others.

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The voltage produced supplies the electrons in an atom with the energy that they need to shift

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towards other atoms through conductive materials. Direct current is produced by cells, batteries,

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photovoltaic panels, dynamos, etc. It is a continuous current in which the electrons always

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move in the same direction, from the negative terminal to the positive terminal of the cell

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or power source. It provides low voltage values. Alternating current is produced by power plants

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and alternators. The direction of this current changes cyclically. In this type, the terminals

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of the power source periodically change polarity. Therefore, the movement of the electrons,

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which is always from the negative to the positive terminal, also changes periodically.

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Alternating current is easier to produce and transmit. It is the electric current in our

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homes and it is used by most electrical appliances. It supplies high voltage values.

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All these electric devices can be usually found in your homes. Some of them are plugged directly

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to the current, for example toasters and lamps, and the washing machine. The majority of them

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are using alternating current because it is the most common and you can get the high voltages.

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But others, like the laptops and the TV, they use a transformer so they transform the usual

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alternating current that is given by in the voltage of 235 volts into the normal 15 volts

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that you need in this kind of devices. And of course, all the devices that use

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batteries or cells, they are using direct current.