gauthamtechie,
What is the difference between the terms insulator and dielectric? what do they mean?
An insulator is a substance that holds onto its valance electrons tightly, so very few charge carriers are available to support conduction. A dielectric is capable of being polarized, i.e., one side of its molecule has a different charge than the opposite side. This forms a electrostatic dipole that increases the capacitance of a capacitor. Those terms are not interchangable. A dielectric must also be an insulator within its voltage range or the cap is considered "leaky". I don't know of any really good insulators that are also really good dielectrics.
Is capacitor as a whole a dielectric or the air between the plates alone called dielectric? And how is semiconductor related to either dielectric of insulator??
thanks in advance! .
As a whole, no. A cap has plates, leads and a protective coating besides a dielectric. A vacuum, also known as "free space", has a relative dielectric constant (also known as relative permittivity) of 1. The dielectric of vacuum is the standard for which other materials are compared. Air has a dielectric constant close to 1, mica is 6.0. A material that polarizes easily makes a better dielectric. In a parallel plate capacitor, the capacitance is directly proportional to the dielectric constant.
A semiconductor is ultra pure crystalline silcon to which a controlled relatively small amount of "dopant" is added. This makes it conduct it better than a insulator but less than a metallic conductor. It would not be a very good dielectric because it would leak badly. It goes beyond the scope of your question to discuss semiconductors further.
Is it then right to say an insulator always remains a "non-conductor" of electricity/heat, Whereas a dielectric can store charge if maintained at the right potential??
ANd so is Air an insulator or dielectric? .
Any insulator will pass a minute amount of charge if the voltage is high enough. A dielectric does not store charge. As part of a capacitor, it stores energy. The amount of charge carriers in a cap at 100 volts is the same as at 0 volts, but the energy stored is much higher. A capacitor is never "charged", it is energized.
poluekt ,
Therefore, dielectric materials with high dielectric constants are considered insulators." (from wiki)
Nope, the dielectric constant and conductivity are two independant parameters. If Wiki said that, they are wrong. A high dielectric constant means the material polarizes easily.
Air is a good insulator, but not much better than vacuum for dielectric constant value.
Ratch