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| Sunday, 26 June 2005 |
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Junior Observer |  |
| News Business Features Editorial
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The many uses of electricity
The electricity that we get from power outlets and batteries can power all kinds of different devices. Electricity can be used in a thousand different ways. Electricity starts with electrons. If you already know how atoms work, you know that every atom contains one or more electrons. You also know that electrons have a negative charge. In many materials, the electrons are tightly bound to the atoms. Wood, glass, plastic, ceramic, air and cotton are all examples of materials in which electrons stick with their atoms. Because the electrons don't move, these materials cannot conduct electricity very well, if at all. These materials are electrical insulators. Most metals have electrons that can detach from their atoms and move around. These are called free electrons. Gold, silver, copper, aluminum and iron all have free electrons. The loose electrons make it easy for electricity to flow through these materials, so they are known as electrical conductors. They conduct electricity. The moving electrons transmit electrical energy from one point to another. One important fact about electricity is that it needs a conductor in order to move. There also has to be something to make the electricity flow from one point to another through the conductor. One way to get electricity flowing is to use a generator. A generator uses a magnet to get electrons moving. There is a definite link between electricity and magnetism. If you allow electrons to move through a wire, they will create a magnetic field around the wire. Similarly, if you move a magnet near a wire, the magnetic field will cause electrons in the wire to move. A generator is a simple device that moves a magnet near a wire to create a steady flow of electrons. A simple way to think about a generator is to imagine it acting like a pump pushing water along. Instead of pushing water, however, a generator uses a magnet to push electrons along. In an electrical circuit, the number of electrons that are moving is called the amperage or the current, and it is measured in amps. The "pressure" pushing the electrons along is called the voltage and is measured in volts. Whether you are using a battery, a fuel cell or a solar cell to produce electricity, there are three things that are always the same: * The source of electricity will have two terminals: a positive terminal and a negative terminal. * The source of electricity (whether it is a generator or battery) will want to push electrons out of its negative terminal at a certain voltage. For example, an AA battery typically wants to push electrons out at 1.5 volts. * The electrons will need to flow from the negative terminal to the positive terminal through a copper wire or some other conductor. When there is a path that goes from the negative to the positive terminal, you have a circuit, and electrons can flow through the wire. * You can attach a load of any type (a light bulb, a motor or a TV) in the middle of the circuit. The source of electricity will power the load, which will function (create light, spin a shaft or generate moving pictures). Electrical circuits can get quite complex. But at the simplest level, you always have the source of electricity (i.e. a battery), a load (a light bulb or motor) and two wires to carry electricity between the battery and the load. Electrons move from the source, through the load and back to the source. Moving electrons have energy. As the electrons move from one point to another, they can do work. In an incandescent light bulb, for example, the energy of the electrons is used to create heat, and the heat in turn creates light. In an electric motor, the energy in the electrons creates a magnetic field, and this field can interact with other magnets (through magnetic attraction and repulsion) to create motion. The three most basic units in electricity are voltage (V), current (I) and resistance (r). Voltage is measured in volts, current is measured in amps and resistance in ohms. There is a basic equation in electrical engineering that states how the three terms relate. It says that the current is equal to the voltage divided by the resistance. I = V/r Batteries, fuel cells and solar cells all produce something called direct current (DC). The positive and negative terminals of a battery are always positive and negative respectively. Current always flows in the same direction between those two terminals. The power that comes from a power plant, on the other hand, is called alternating current (AC). The big advantage that alternating current provides for the power grid is the fact that it is relatively easy to change the voltage of the power, using a device called a transformer. By using very high voltages for transmitting power over long distances, power companies can save a lot of money. ########## Advantages of fibre optics We introduced you to fibre optics in a recent issue of the Junior Observer. Today we'll tell you more about their advantages. * Less expensive - Several miles of optical cable can be made cheaper than the same amount of lengths of copper wire. This saves the provider (cable TV, Internet) and you money. * Thinner - Optical fibres can be drawn to smaller diameters than copper wire. * Higher carrying capacity - Because optical fibres are thinner than copper wires, more fibres can be bundled into a given-diameter cable than copper wires. This allows more phone lines to go over the same cable or more channels to come through the cable into your cable TV box. * Less signal degradation - The loss of signals in optical fibre is less than in copper wire. * Light signals - Unlike electrical signals in copper wires, light signals from one fibre do not interfere with those of other fibres in the same cable. This means clearer phone conversations or TV reception. * Low power - Because signals in optical fibres degrade less, lower-power transmitters can be used instead of the high-voltage electrical transmitters needed for copper wires. Again, this saves your provider and you money. * Digital signals - Optical fibres are ideally suited for carrying digital information, which is especially useful in computer networks. * Non-flammable - Because no electricity is passed through optical fibres, there is no fire hazard. * Lightweight - An optical cable weighs less than a comparable copper wire cable. Fibre-optic cables take up less space in the ground. * Flexible - Because fibre optics are so flexible and can transmit and
receive light, they are used in many flexible digital cameras in medical
imaging and mechanical imaging. |
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| Politics | Produced by Lake House |
Can you think of a life without electricity? Imagine reverting to
fireplaces for heat, wood-fire stoves for cooking and candles for light.
There is no doubt that for most of us, life would be impossible without
electricity. But how many of us actually know what this mysterious stuff
we call electricity is? Where does it come from, and why is it able to do
so many different things? 
