Conducting materials are the materials that are used for the conduction or passage of electrical current from one point to the other in order to get some gainful work done. These materials are of extreme importance because electricity today is a basic need and a fundamental raw material in almost all industries and production units.
Classification of materials based on their conductivity is important to differentiate them as good conductors, bad conductors, or insulators and semiconductors. Each of them has its own specified functional importance.
The most important and major classification of conducting materials can be done based on their conductivity. The conductivity of a given material is the ease with which an electric current can pass through it at a given voltage. Mathematically, the conductivity can be represented as
Where σ is the conductivity of a material, R is the Ohmic resistance of the material, L is the length of the material in meters and A is the area of cross-section of the material in meter2.
For a given material of a certain length and area of cross-section, conductivity is inversely proportional to the resistance of the material which impedes the flow of current through the material. Conductivity is also denoted by
Where G=1/R is the conductance of the material in Siemens.
Resistivity is the reciprocal of the conductivity of a material.
Classification of Conducting Materials
Now as we have understood conductivity, we can classify conducting materials into three types.
- High Conductivity Materials
- Semi Conductive Materials
- Low Conductivity Materials
1. High-Conductivity Conducting Materials
High Conductivity Materials, as the name says, are the materials that fall under good conductor specifications. These high-conducting materials have low resistance and greater conductance. Low resistance causes lesser voltage drop and heat loss across these materials when a certain amount of electric current passes through them. This is because the heat loss and the voltage drop within a material are directly proportional to the resistance the material offers to the flow of current.
Low voltage drops within these materials make them efficient conductors and these materials are used in places where continuous flow of electric current is required over a given period of time.
Examples of High Conducting Materials: All metals like Copper, Aluminium, gold, etc. fall under high conductivity materials. Copper and Aluminium are extensively used in the field of Electrical Engineering owing to their economic value and performance.
Metals have good conductivity because all metals have loosely bound electrons in the outer shell of their atomic structure which can be detached easily by application of a certain voltage. These electrons come out of their shells and roam around as free electrons. Electrons are charge carriers and hence these electrons help in the flow of electric current over a given period of time. Graphite is the only non-metal which has good conductivity like that of metals.
Places, where materials of high conductivity are required, are the Transmission and Distribution of power through conductors, Household appliances and wiring, electrical machines like Motors and Generators, Industrial robotics, etc.
Examples of High- Conductivity Conducting Materials
Copper
It will be an incomplete discussion if high conductivity conductive materials are discussed without taking the example of Copper. Copper is the most used conducting material and one of the best conductive materials available. It is readily available from the mines and cheaper in cost than other metals. Apart from that, the excellent physical properties of the material make it an ideal choice for manufacturers.
There are chiefly two types of Copper that are used in industrial applications – Annealed Copper and Hard-drawn Copper.
Annealed Copper: It is flexible in nature and has a resistivity of 1.72 X 10-8 Ohm-m. Hence it is used in places where higher flexibility is required like the winding of electrical machines, Transformers, flexible links in busbars, etc.
Hard-drawn Copper: It has higher tensile strength although with higher resistivity as compared to Annealed Copper( 1.77 X 10-8 Ohm-m). These are used in places where higher tensile strength is required and resistivity is not a particular concern like in Transmission and Distribution lines.
Silver
It is the best-conducting material among the metals known to us as of now and even better than Copper. However, it is costlier than copper and it oxidizes easily when comes in contact with the air which is why it is not used in place of copper in various applications.
Silver is much harder than copper and is more resistant to corrosion as compared to Copper. Hence it is used to coat or encase the copper wire to improve the overall durability of the system.
Gold
Gold is an excellent conducting material for electricity. However, its limited availability and ornamental value limit its usage in industrial applications.
Gold is used in making connectors, switches, and semiconductor devices to improve their speed and durability against corrosion.
Brass
An alloy of Copper(60%) and Zinc(40%). Brass is resistant to corrosion and doesn’t get oxidized easily while being exposed to air. However, its conductivity is less as compared to pure copper.
Brass is used in making switches, connectors, rheostats, socket outlets, etc.
Bronze
Bronze is an alloy of Copper(90%) and Tin(10%). It has better corrosion resistance than that Brass but has lower conductivity as compared to Copper.
Bronze is used in making current-carrying springs and contacts, brush-holders, sliding and boiler parts, etc.
Aluminum
Aluminum is the most preferred conducting material followed by copper. It is ductile and malleable and has a lower weight per unit length as compared to copper. Hence it is used in making transmission lines instead of copper because lower weight causes lower sag in the lines, as well as the stress on the contact points, is low.
2. Semi-Conductive Materials
Semi-conductive materials are the ones that have their conductivity lying between the conductors and the non-conductors or the insulators. These materials have conductivity lower than the conductors but higher than non-conductors. Semi-conductive materials are made up of metalloids which have the characteristics of both metals as well as non-metals.
Semiconductor materials are Silicon, Germanium, Galium Arsenide, etc.
Semiconductive materials are used in making power-electronic devices like MOSFET, IGBT, GTO, and BJT as well as other electronic switches like transistors and integrated circuit chips which require high-frequency two-stage switching.
Semi-conductive materials are used to make them because their conductivity can be changed within a very small fraction of time. This allows them to act as high-frequency switches. The table of resistivity of different materials is shown in the below pic.
3. Low-Conductive conducting Materials
The Low-conductive material has lower conductivity compared to high-conductive materials. The followings are the low-conducting materials.
Manganin
It is an alloy of 84.2% Copper, 12.1% Manganese, and 3.1% Nickel. It is a high-resistivity material used for making standard resistance coils and shunts for measuring devices.
Constantan
Constantan is the result of improvement over Manganin. It is an alloy of 55% Copper and 45% Nickel. It has a low thermal variation of resistivity which makes it ideal for making thermocouples and low-temperature heating resistance materials.
Nichrome
Nichrome is an alloy of Nickel and Chromium with a trace amount of iron. It is commonly used for making resistance wires and in heating elements like electric heaters, kettles, and toasters.
Tungsten
Tungsten or Wolfram is a metal with an excellent melting point which makes it an ideal choice for making bulb filaments and cathode-ray tubes. Tungsten has a melting point of 3422 deg.C in an inert or vacuum medium and above 1650 deg.C, it has the highest tensile strength.
This is all about the classification of electrical conducting materials.