Conductors and Insulators in Solid State

What is a Conductor?

Conductors refer to certain kind of materials or objects that permits the flow of electric current (charge) in one or more than one direction. The materials which are made up of metals are the common conductors of electricity. Electrical current is produced by the flow of positively charged holes, negatively charged electrons and +ve or –ve ions in few cases.

For the flow of current, a charged particle does not need to move from a system or machine generating the current to the one consuming it. Rather, transfer of a long chain of momentum takes place between mobile charge carriers. Due to this momentum transfer, metals are the ideal choice for conductors. Metals hold a sea of electrons which are delocalised, thereby giving the latter ample mobility for collision and so momentum transfer occurs.

As said before, electrons are considered the fundamental mover in metals, but some other devices like a proton conductor's mobile protons or cationic electrolytes of batteries rely on +ve charge carriers.

Next, let us proceed with the materials and uses of conductors.

Conductor Materials and its Uses

The materials used as conductors include:

• Metals

• Electrolytes

• Superconductors

• Semiconductors

• Plasmas

Some nonmetallic conductors are:

• Graphite

• Conductive polymers

A high conduction metal is copper. The international standard used to compare other electrical conductors is annealed copper. Conductivity of Internal Annealed Copper Standard is 58 MS/m. However, ultra-pure copper can exceed 101% IACS. Electrolytic tough pitch (ETP) copper is the main grade copper which is utilised in making building wires, cables, motor windings, busbars, etc.

The conductivity of silver is 6 per cent more than that of copper, but because of its high price, it is practically not used in maximum cases. Though, silver metal is used in special pieces of equipment like satellites and thin platings to reduce skin effect losses at elevated frequencies.

Another common metal used as a conductor is aluminium. Wires made of aluminium are widely used in electric power distribution and transmission. However, it has a disadvantage as well. Aluminium quickly gives rise to an insulating oxide which heats the connections.

Pure water is a bad electrical conductor, but if a bit of ionic impurity is added to it (like salt), water becomes a conductor.

Did You Know?

14,700 short tons of silver were taken on loan from Treasury to make calutron magnets in the time of World War II as there was a shortage of copper.

Now that you have read about conductors, let us move to the next topic – insulators.

What is an Insulator?

A material which does not allow the free flow of electrons or the atom of the material hold tightly bound electrons, whose charges cannot flow freely, is called an insulator. In these types of materials, electric current at a very low amount can flow under the effect of an electric field. Insulators are just the opposite of conductors and are also known as bad conductors of heat and electricity. The fundamental property that separates an insulator is resistivity. Insulators are highly resistant, and non-metals are the common examples that fall under this category.

There is no existence of an ideal insulator because insulators also contain small amounts of charge carriers which help in carrying current. Moreover, when there is an application of a large voltage on insulators, it becomes electrically conductive because the electrical field pulls apart the electrons from atoms. This is called a breakdown voltage of insulators. Some examples of electrical insulators that have high resistivity are:

• Glass

• Paper

• Teflon

• Rubber-like polymers

• Maximum plastics (thermoplastic or thermoset)

Applications of Insulators

Insulators are mainly used to separate and support electrical conductors to restrict the flow of current through themselves. Insulation is the process of wrapping up of electrical cables or other types of equipment using an insulating material in bulk. These materials are also utilised to fasten electric power transmission or distribution lines to transmission towers and utility poles. They hold the weight of hanging wires without permitting current flow through the tower to the ground.

There are few wires which have mechanical coverings where there is no voltage rating given like service drop, doorbells, welding, thermostat wire, etc. A wire which is insulated holds a voltage rating and the highest conductor temperature rating. However, it may not have a current-carrying capacity rating because this type of rating is dependent on the surrounding environment.

Apart from using in wires, the following are some other uses of bad conductors of heat and electricity.

1. In electronic units, printed circuit boards are constructed from fibreglass and epoxy plastic. These insulating boards assist the conductive copper foil layers. Moreover, the delicate and small active components are inserted within insulating phenolic or epoxy plastics or inside ceramic coatings or baked glass.

2. The silicon matter inside microelectronic components like integrated circuits and transistors is a conductor due to doping. However, it can be feasibly converted into an insulator by applying oxygen and heat. Silicon on oxidisation becomes quartz which is silicon dioxide, the fundamental element of glass.

3. Liquid insulator oil in high voltage units consisting of capacitors and transformers prevents arcs. The spaces are replaced by oil that supports considerable voltage without electrical breakdown. Some other insulation materials used in high voltage devices are glass or ceramic wire holders, vacuum, gas, etc. Placing wires at a significant distance so that air can be used as insulation is another commonly used method.

Besides conductors and insulators, there is another type of a solid known as semiconductors. By going through the next section, you will get an idea about semiconductors in chemistry.

What is a Semiconductor?

A material whose electrical conductivity value falls between an insulator like glass and a conductor like metallic copper is called a semiconductor. The resistance of these kinds of materials reduces with a rise in temperature. The conducting properties of semiconductors can be modified in productive ways by doping (introducing impurities) into the structure of the crystal. When there is an existence of two distinctively doped regions, a semiconductor junction is formed. At these joints, the traits of charge carriers like ions, electrons and electron holes are based on transistors, diodes and modern electronics.

Semiconductor Materials

Silicon and gallium arsenide are the two most widely used semiconductor materials which are used in solar cells, laser diodes, microwave frequency circuits, etc. Moreover, silicon is a crucial material in making of most electronic circuits.

Silicon's conductivity is enhanced by adding a small quantity of trivalent (gallium, indium and boron) and pentavalent (phosphorus, arsenic or antimony) atoms. The resulting semiconductors are called extrinsic or doped semiconductors. Other than the process of doping, a semiconductor's conductivity can be increased by escalating its temperature. This is just the opposite property of a metal where conductivity reduces when the temperature is increased.

Apart from silicon and gallium arsenide, germanium, specific ternary compounds, alloys, oxides, and organic compounds are examples of semiconductor materials.

The common semiconducting substances are crystalline solids, but liquid and amorphous semiconductors are also available. They include mixtures of selenium, tellurium and arsenic in various proportions, and hydrogenated amorphous silicon.

Did You Know?

The first real-life semiconductor application in electronics was the construction of cat's whisker detector in 1904, which was used in traditional radio receivers.

Uses of Semiconductors

Semiconductor tools can exhibit various useful properties like easy passing of current in one direction, showing varying resistance and vulnerability to heat or light, etc. Since the electrical characteristics of a semiconductor substance can be changed by doping, or by applying light or electrical fields, tools made from semiconductors can be utilised for switching, amplification and energy conversion.

Do It Yourself

1. Choose the Correct Option about Insulators and Conductors.

1. A conductor allows the flow of electricity and insulator does not.

2. An insulator allows the flow of electricity and conductor does not.

3. Conductors are magnetic, and insulators are not.

4. Insulators are magnetic, and conductors are not.

The above discussion on conductors, insulators and semiconductors are vital topics of your curriculum. You can access detailed notes on them from Vedantu website. For more related topics, you can download our Vedantu app too and get easy access to our online interactive sessions as well.