What does a conductor do to the overall dielectric constant? (see details)?

Question

If I had a +ve metal plate and a -ve metal plate, separated by a sandwich construction of insulator, conductor, insulator; then what would be the effective dielectric constant of the sandwich construction?

Would the inclusion of the conductor increase or decrease the effective dielectric constant (compared to just having the insulator alone)?

I have a list of dielectric constants:

http://www.clippercontrols.com/info/dielectric_constants.html#S

but no conductors there.

Please note that the conductor in the "sandwich" is not short circuited in any way.

Please go easy on the maths, cause that's not really my strong point!!!!!!

This may be a stupid question; but I won't know that till I read the answers!

I hope this makes sense!

Answer 1

Okay simply enough, you can't find conductors in the list because dielectric contants apply only to electrical insulators and so have a constant of 0.

I don't remember exactly but i think dielectric constant was originally defined by faraday as the abilily of a material to change the capcitance when placed in an electric field.

therfore since your putting something in between the plates with a constant of 0 if will have no effect.....however, if i've got my head screwed on right today, i think you may see a very minor change simply because by putting the conductor there you are displacing air which has a permability of 1. but it would be a very minor change...If you do see a change in capacitance then there's probally something wrong with your setup.

Answer 2

Since the pieces of metal are not connected to anything, they have no current flow and have no charge separation, they might as well not be there. In other words, they have no effect at all.

If you took them out and moved the two end plates closer (by the thinckness of the removed plates) to compensate, nothing would change, except possibly some edge effects. Capacitance would be the same, dielectric constant would be the same.

Answer 3

Well thickness of the conductor is a part of the equation.  

If you take a stack like you have that has all the conductors  connected to voltage and compare it to a solid chunk of conductor connected to voltage, your stack will have a signifigantly higher dielectric.

The more stacking you can get with the same height, the higher the dielectric.

If your voltage is high enough you might get some inductance going on with your stack if the sandwiched condoctors aren't connected to a voltage.  I'm not sure what would happen then.

Answer 4

If the inner conductors are not connected to anything, but simply support the physical structure, you essentially have a collection of small capacitors in series.  I'd predict the total dielectric constant to be unaffected by the addition of unconnected conductors.

If, on the other hand, you alternately wire conductive plates to +ve and +ve, you've got the equivalent of a collection of small capacitors in parallel, effectively increasing the total plate area.

Either way, my instinct is no change in dielectric.

Answer 5

You cant change the dielectric constant of a material.  the dielectric constant is used to work out the proportions of the conductor and insulator for certain line impedances etc. an example of this is 75ohm tv ariel cable ptfe and air are common dielectrics (air being 1 and ptfe being 2.  the different constants mean different size insulators to get the same impedance