what is a dielectric?? how is it related to dielectric strength?(water's dielectric strength is 81 ... what does it mean?

what is a dielectric?? how is it related to dielectric strength?(water's dielectric strength is 81 ... what does it mean?


2 Answers

kushagra abhishek
23 Points
13 years ago
Ramesh V
70 Points
13 years ago

A dielectric is a material that restricts the flow of current. Dielectrics are defined by their dielectric constant, current leakage, and breakdown voltage. They are mainly used in capacitors, allowing charge to build up on the conductive plates. An insulator is a dielectric than can withstand a high electric field without letting current flow through it.

Dielectric strength:
Dielectric strengthis the ability of an insulator to withstand potential difference. It is usually expressed in terms of the voltage at which the insulation fails because of the electrostatic stress. Maximum dielectric strength values can be measured only by raising the voltage of a TEST SAMPLE until the insulation breaks down.

Water as dielectric:

Water does indeed have a very high dielectric constant(81) - this is because the water molecule has a dipole moment and so water can be polarized.  That is, under a given electric field, water tends to polarize strongly, nearly canceling out the effect of the field.  However,water also conducts electricity (why it is dangerous to play with electrical equipment in the bath for instance) because it always contains ions (OH- and H+ are always there, and also things like Cl- and Na+ are usually present) which are highly mobile.

Capacitors have a dielectric layer between their conductive layers to increase their capacitance, and are defined by the type of material used. Typical dielectrics include paper, polyester film, mica, polystyrene, polypropylene, ceramic, and tantalum oxide.


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Naga Ramesh
IIT Kgp - 2005 batch

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