In electrical engineering, different types of materials are used for manufacturing of electrical products and equipment. Any material in real life can have different properties and characteristics, which can be used appropriately for better utilization. But electrically a material can be classified as either insulator or conductor and semi-conductor.
The property which makes a material insulator, conductor or semiconductor is called electrical resistivity. The electrical resistivity is the measure of how difficultly a material passes a current. Which depends upon the availability of free electronic or ions. The more free-electrons/ion available at a body the more it will be a conductor and fewer electrons/ions mean insulator.
Electrical resistivity is the resistance of a one-meter cube volume wire, its SI unit is Ohm-Meter (Ω-m) and represented with Greek letter ρ (ROH). Electrical conductivity is the reciprocal of resistivity and means measure the ability to conduct an electric current and SI unit is Siemens/meter (S/m). The resistivity/conductivity of material varies from material to material.
What is Conductor?
Conductors are type materials which pass electric current in it because of availability of free electrons. An electrical conductor has low resistivity and high conductivity. The resistivity of a conductor is from zero to 10-4 Ohm-meter. The conductor has plenty of free electrons in it, a small potential can cause the flow of electrons.
One of a good example of a conductor is metal, where there are very few valence electrons in the outermost shell of each atom and they are loosely attracted to the nucleus. A very little energy can extract them out of the atom orbit and make them free electrons.
Electrical wire is made of conductors which carry current from source to load. Best electrical conductor examples are copper, silver, gold, etc.
What is Insulator?
Insulators are the type of electrical material which possesses high resistivity more than 104 Ohm-meter, or inversely low conductivity. There almost no free electrons available for carrying current in insulators. A large voltage in insulator may not cause current but in some cases a very small leakage current because of unavailability of free electrons.
Most non-metals are insulators, where bonds have the desire to catch more electrons. Therefore, a significant amount of external energy may not able to extract an electron free. In ionic material, all the ions are arranged together such that there are no carries available for current to carry.
Insulators are used to support conductor, avoid electric shock and all those paths where no current is intended. The best insulators are ceramics, plastic, wood, etc.
What is Semiconductor?
The semiconductor has the resistivity between 10-4 and 104 ohm-meters. At normal temperature, the resistivity of a semiconductor is comparatively high but as temperature increase, the resistivity decreases. A semiconductor is mostly having four electrons in its valence shell and belong to coulomb 3 and 4 of the periodic table.
The number of free electrons in a semiconductor are very few at ambient temperature, where external energy i.e. increase in temperature can increase the number of free electrons. A semiconductor is the basis of modern electronics. The best example of a semiconductor is Germanium, Silicon and Gallium Arsenide etc.