Insulator vs Dielectric
An insulator is a material which does not allow the flow of electric current under the influence of an electric field. A dielectric is a material with insulating properties, which polarizes under the effect of an electric field.
More about Insulator
Resistance to the flow electrons (or current) of an insulator is due to the chemical bonding of the material. Almost all the insulators have strong covalent bonds inside, so the electrons are tightly bound to the nucleus heavily restricting their mobility. Air, glass, paper, ceramic, Ebonite and many other polymers are electric insulators.
As opposed to the use of conductors, insulators are used in situations where current flow has to be stopped or restricted. Many conducting wires are insulated with a flexible material, to prevent electrical shock and interference with another current flow directly. Base materials for printed circuit boards are insulators, allowing controlled contact between the discrete circuit elements to be made. Supporting structures for the power transmission cables, such as bushing are made out of ceramic. In some cases, gases are used as insulator, most commonly seen example is high-power transmission cables.
Every insulator has its limits to withstand a potential difference across the material, when the voltage reaches that limit the resistive nature of the insulator breaks, and the electric current starts to flow through the material. The most common example is lightening, which is an electrical breakdown of air due to enormous voltage in thunderclouds. A breakdown where the electrical breakdown occurs through the material is known as a puncture breakdown. In some cases, air outside a solid insulator might get charged and break down to conduct. Such a breakdown is known as a flashover voltage breakdown.
More about Dielectrics
When a dielectric is placed inside an electric field the electrons under the influence move from its average equilibrium positions and align in a way to respond the electric field. Electrons are attracted toward the higher potential and leaves the dielectric material polarized. Relatively positive charges, the nuclei, are directed towards the lower potential. Because of this, an internal electric field is created to the direction opposite to the direction of the external field. This results a lower net field strength inside the dielectric than the outside. Therefore, Potential difference in the dielectric is also low.
This polarization property is expressed by a quantity called dielectric constant. Material which has a high dielectric constant are known as dielectrics, while materials with low dielectric constant are usually insulators.
Mainly dielectrics are used in capacitors, which increase the capacitor’s ability store surface charge, hence giving a greater capacitance. Dielectrics that are resistant to ionization is chosen for this, to allow greater voltages across the capacitor electrodes. Dielectrics are used in electronic resonators, which exhibit resonance in a narrow frequency band, in the microwave region.
What is the difference between Insulators and Dielectrics?
• Insulators are material which are resistant to electric charge flow, while dielectrics are also insulating materials with special property of polarization.
• Insulators have a low dielectric constant, while dielectrics have relatively high dielectric constant
• Insulators are used to prevent charge flow while dielectrics are used to improve the charge storage capacity of capacitors.