Category Electricity

What is a superconductor?



               When electrons flow through a conductor they collide with atoms and electrical energy is gradually lost in the form of heat. This process is called electrical resistance. However, when some substances become very cold, all electrical resistance is lost and the current flows freely without loss of energy. These substances are called superconductors. Their use allows some devices to work faster and more efficiently than ever before. Because of the difficulty in keeping superconductors cold, their use is limited. In the future, superconductors may be used to make efficient computers.

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What is alternating current?


                Electrical currents normally flow in one direction through an electrical conductor. This kind of electricity, which is produced by batteries for example, is called direct current. When the electrical current is made to reverse its direction rapidly, it is known as alternating current. This kind of electrical current is used in domestic wiring, and it usually switches direction and back again about 50 to 60 times per second. This is the cause of the hum that you can sometimes hear near electrical equipment such as fluorescent lights.

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How does electricity produce heat and light?

            A good conductor such as copper has only very low electrical resistance. It does not get very hot when electricity flows through it, making copper suitable for household wiring.

            Other metals such as iron and nickel have much greater resistance to the passage of electricity, so they become hot. A very thin wire has more resistance than a thick one, and a long wire has more resistance than a short wire. In an electric fire, coils of thin, high-resistance wire glow and produce heat when an electrical current passes though them.

            In a light bulb, coils of an extremely thin conductor ensure that heat cannot be radiated away quickly enough and some of the energy is converted to light.

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How do batteries work?

               Batteries produce electricity by means of chemical action. A battery contains two different conductors, or electrodes. Usually, one of these is the metal case of the battery. The electrodes are separated by a conducting liquid or paste, called the electrolyte. The substances in the battery react chemically with each other to produce an electrical current. As a result of chemical activity a positive charge builds up at one electrode, and this can flow through a conductor such as a wire to the other (negative) electrode. Eventually the chemical energy runs out and the battery becomes exhausted.

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How is electricity made?

               Energy cannot be created. An electrical generator is simply a means of converting mechanical energy into electrical energy. In its simplest form, a generator spins coils of wire in a magnetic field, causing the flow of electrical current in the conducting wire. The power to spin the generator comes from other forms of energy. This energy might be stored energy in fossil fuels such as coal or oil, hydroelectric power from dams, wind power from turning huge windmills, or nuclear power produced by the radioactive decay of elements. In all these cases, one form of energy is simply converted into electrical energy.

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