Answer to Question #200077 in Electrical Engineering for McKenzie

Question

Conductor’s properties: e.g. conductivity, resistivity, corrosion resistance, tensile strength and rigidity (hardness and toughness).

Solid conducting materials: e.g. copper, aluminium, steel, brass, carbon, soil (for earth continuity).

Liquid and gas conductors: e.g. electrolytes, conductive gases in fluorescent and discharge lighting.

A. Select one solid and one liquid or gas conductor from the list above. For each of them describe their properties in terms of: conductivity, resistivity, tensile strength and rigidity (where applicable). Then give an example of an electrical use for each of them.

B. State which of its properties makes them suitable for its electrical use.

Answer 1

Solid

Aluminium is the solid electrical conductor I'm going to discuss. Aluminium (also known as Al) has the atomic number 13 and is a metal. Aluminium has a lower density than the other main metals, around one-third that of steel, and it has a strong affinity for oxygen, forming a protective coating of oxide on the surface when exposed to air. Aluminium mimics silver in appearance, both in color and in its ability to reflect light. It is pliable, nonmagnetic, and ductile. Aluminium is a great thermal and electrical conductor, with approximately 60% of the thermal and electrical conductivity of copper while having just 30% of copper's density. Aluminium is superconducting, having a superconducting critical temperature of 1.2 kelvin and a critical magnetic field of roughly 100 gauss (10 milliteslas). It is also paramagnetic, therefore it is unaffected by static magnetic fields. However, because of its high electrical conductivity, it is significantly impacted by alternating magnetic fields via the induction of eddy currents. The resistivity of a 100km piece of aluminum is 13.5m. 237 W(m-k) thermal conductivity and 26.5 nm electrical resistance (at 20 C). An aluminum atom possesses 13 electrons, 3 of which are free to travel inside it. This enables heat and electricity to be freely transported throughout the metal.

Because of their low resistance and great conductivity, copper and aluminum are the most often utilized electrical conductors in electrical cables. These metals are both ductile and corrosion-resistant, but they also have unique qualities that make them suitable for a variety of applications. Copper is the more conductive of the two metals; in fact, only silver is more conductive among the regularly available pure metals, although it is significantly more costly and not as strong.

Aluminium is plentiful and a less expensive alternative to copper for conductors. Copper's demand is changeable, therefore its price varies significantly, but aluminum's pricing is much more consistent. While an aluminum conductor is only approximately 61% as conductive as a copper conductor of the same size, it is three times lighter, making it considerably simpler to handle. As a result, aluminum is used in big size cables and cables for overhead power distribution.

Because of the difference in conductivity, a significantly bigger size aluminium conductor is required to equal the conductivity of the corresponding copper wire. Using a larger size conductor requires more insulation material to adequately cover the conductor, and the extra cross-sectional size of the cable may be restrictive in certain applications.

Tensile strength is another difference between the two - copper has around double the tensile strength of aluminum, although it is worth noting that because the corresponding aluminium conductor is larger and lighter, it frequently does not require the same degree of tensile strength. Copper is more thermally conductive than aluminum, however the differences are decreased when bigger conductor diameters are considered. The better the thermal conductivity, the better the conductor's short circuit performance.

In some cases, copper-clad aluminium conductors consisting of an aluminium core with a heavy skin of copper bonded to the aluminium can be used. Whilst not in widespread use, this conductor type does combine the advantages of the lighter weight aluminium with the more conductive

the metal copper However, the ductility is that of aluminum rather than the increased performance of copper. This conductor type has gained popularity as a lightweight center conductor in coaxial cables. Because the wire is less in weight, a lower density dielectric material may be used for improved attenuation.

Liquid or gas

Electrolytes in batteries and gasses used in fluorescent and discharge lighting are examples of liquid and gas conductor materials. Plasma has an extremely high conductivity since it is ionized. As a result, it may conduct electricity. This is accomplished by heating it or exposing it to an extremely strong electromagnetic field, which is typically generated by a laser or a microwave generator. This has an influence on the gas by increasing or decreasing the quantity of electrons within it. This process generates charged particles like ions. When there are a lot of ions in the gas, it becomes electrically conductive and reacts very strongly to electromagnetic fields. This indicates that it is an excellent conductor. Plasma has a resistivity of 0.2 – 1.5eV, indicating that it is not particularly resistant.

A plasma globe is a common use of plasma. It is a glass sphere containing a mixture of noble gases such as argon, krypton, and xenon, with a high voltage electrode in the center. Plasma filaments stretch from the electrode to the outside glass shell/insulator, creating the illusion of a continual beam of light following you when you are touched. It is powered by a high frequency (35kHz) alternating current at 2-5kV. The high voltage electrode in the center then serves as a transformer to increase the voltage, allowing the light streams to occur. Placing a finger on the glass provides an appealing location for energy to flow through. Because the human body is conductive (has a non-ohmic resistance of close to 100 ohms at ambient temperature), it is simpler to polarize than the dielectric material around the center electrode by offering an additional discharge channel with less resistance.