# Parallel plate capacitor and insulating material

• tarellan
In summary, for a parallel-plate capacitor with plates of 10 cm^2 area separated by a 0.10mm layer of glass insulation with resistivity rho = 1.2x10^13 omega*m and dielectric constant k= 5.6, the time constant for discharging through its insulation is 590s. This shows that the dependence is not on the dimensions, but rather on the properties of the insulating material. This is evidenced by the fact that the RC value does not vary significantly with changes in cross sectional area.

## Homework Statement

A parallel-plate capacitor has plates of 10 cm^2 area separated by a 0.10mm layer of glass insulation with resistivity rho = 1.2x10^13 omega*m and dielectric constant k= 5.6. Because of the finite resistivity, current can leak through the insulation.

How do I Show that it depends only on the properties of the insulating material and not on its dimensions?

C= emf(A/d)

## The Attempt at a Solution

I found the time constant for this capacitor to discharge through its insulation. T= 590s

tarellan said:

## Homework Statement

A parallel-plate capacitor has plates of 10 cm^2 area separated by a 0.10mm layer of glass insulation with resistivity rho = 1.2x10^13 omega*m and dielectric constant k= 5.6. Because of the finite resistivity, current can leak through the insulation.

How do I Show that it depends only on the properties of the insulating material and not on its dimensions?

C= emf(A/d)

## The Attempt at a Solution

I found the time constant for this capacitor to discharge through its insulation. T= 590s

Consider the resistivity

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html#c2

Consider too the equation you have for capacitance.

Notice anything about how - when you combine the 2 - the RC has a tendency not to be dependent on the cross sectional area?