Answer to Question #200078 in Electrical Engineering for Mckenzie

Question

Insulators properties: e.g. resistivity, breakdown voltage, operating temperatures, mechanical strength.

Solid insulating materials: plastics (e.g. PVC), butyl-rubber, glass, varnishes, paper.

Liquid and gas insulating materials: oil, air, sulphur hexafluoride gas.

A. From the list of insulators above select one solid and one liquid or gas. Describe it in terms of resistivity, maximum voltage capacity, operating temperature and mechanical strength.

B. Give an example of where each one is used and state which of its properties makes it useful for the purpose

Answer 1

Solid

Plastic is a form of PVC. This implies it is an excellent insulator. The dielectric strength is measured in terms of how much voltage it can endure without being destroyed. As illustrated in the chart to the right, a greater number indicates better electrical qualities (greater resistivity). The volume resistivity is lower than that of olefin resin products. However, because stronger fire-resistant materials are required for electrical applications, it is extensively employed in a broad range of electrical items such as electrical cables, cars, insulating tapes, wire covers, and much more!

PVC is commonly used in electrical wiring as one example of typical use. This is because it will protect someone from receiving an electric shock. Also, as you know, electrons within a wire, such as copper, flow along and generate heat. This heat can start a fire, but happily, PVC is incredibly heat resistant and will not catch fire when wrapped around a wire.

Liquid or gas

Gases, by definition, are poor conductors and excellent insulators. The air is an example of an excellent gas insulator. Because it keeps current from leaking out of objects like conductor cables. The electrical resistance of air (once ionized) is 21.1 kV/cm or 30kV/cm (peak), which implies that the electrical field required to ionize 1cm of air, allowing electrons to jump into the air, causes it to conduct. We breathe unionized air, which is nonconducting, which is why we do not get electrocuted when we breathe. So, while there are no ions in the air, its conductivity is infinite, but it becomes 21.2 kV/cm when ionized. Another feature is the velocity distribution. Collisions typically result in a Maxwellian velocity distribution of all gas particles, with a few fast particles. This indicates that extremely few particles clash with one another, implying that they cannot conduct electricity.

It is utilized for electrical transmission in one application. The open-air acts as an electrical insulator, preventing electricity from flowing out of the conducting line and onto the ground. Because air is inherently non-ionized, it has little trouble preventing electricity from completing a circuit and electrocuting everything.