Electrical Technology

Topics: Magnetism, Magnetic field, Magnet Pages: 6 (2127 words) Published: October 18, 2010
Electrical technology – assignment 4

Properties of electrical materials and Effective use of technology

P.5. Describe the properties and a typical application of a solid and a liquid or gas electrical conductor.

A conductor is a material that allows free movement of electrons and therefore allows easy flow of electricity. Most conductors are metals. A common metal used as a conductor in electrical technology is aluminium. It is used quite a lot as it cheap, lightweight and in abundance compared with other electrical conductors. Aluminium is used in overhead power cables as it is has many properties which make it ideal for this purpose. It is very easy to work Aluminium can be easily fabricated into various forms such as foil, sheets, shapes, rods, tubes, and wires. It also displays excellent malleability and plasticity in bending, cutting, and drawing. Aluminium does not rust as when it is open to the air a layer of aluminium oxide forms and protects it from corrosion. Earlier on transmission lines were made from copper but this was heavier and recently became more expensive. Conductive Aluminium has relatively low mechanical strength therefore it is either used with steel, or by using an aluminium alloy to help with the mechanical strength that is needed in overhead power lines. Aluminium is a very light metal with a specific weight of 2.7 g/cm3, about a third that of steel. Aluminium’s Electrical Resistivity at 20°C is at 2.69 µΩ.cm. Aluminiums conductivity is around 60% that of copper (coppers being 59.6 × 106 S/m).

Argon is a colorless, odorless, tasteless, and non-toxic gas. It is a good example of a gas that can conduct electricity. It is an inert gas this means that it is none reactive. It is used within bulbs and fluorescent lamps as a substitute for air. If the bulb/lamp is filled with air the filament would oxidise this would cause the bulb to be dimmer this would also be dangerous as the oxygen in air could Cause the filament to burn, so argon is used to prevent any of this happening. Electrical conductivity of argon: 0 mS cm-1

Argon has the ability to be

ionized (become electrically conductive) at lower voltages than most other gases. This is done by heating the gases to a temperature at which it turns to a plasma state, in this state it begins to release electrons which move independently of the atom making it electrically conductive. Argon can be used is also used in fluorescent lamps as a gas which can be conductive when ionized. When it is ionized and electrons are flowing through the argon gas the free electrons bump into gaseous mercury atoms which then get excited and when they return to their normal state the extra energy is given off as light energy (photons) these photons are in the ultraviolet spectrum so we cannot see them. So a phosphor powder coating is used this will give off visible light when the atoms are exited and return to their normal state. Also used in "Geiger" counters, which measure radiation levels.

P.6. Describe the properties and a typical application of a solid and a liquid or gas electrical insulator.

An insulator is a material that blocks the flow of electrical current. An insulator is a poor conductor as it has a high resistance against the flow of electrons. Solid Electrical insulators are commonly used to hold conductors in place such as using porcelain to hold over head cables and to insulate them from the pylon. Other electrical insulators include rubber, plastic, and mica. Porcelain is a commonly used material for the suspension of high-voltage overhead lines as it is a good insulator, but it is brittle. Porcelain insulators are made from clay, quartz or alumina and feldspar they are covered with a glaze to keep away dirt and are shaped as they are to let water run off them. Where a high durability and mechanical strength is needed a porcelain rich in alumina will be used. It has a dielectric strength of about 4–10 kV/mm.

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