# Relative dielectric constant - More than one dielectric in a capacitor

• Gabry89
In summary, the conversation discusses calculating the capacitance of a parallel plate capacitor with two different dielectric materials. The key is to calculate the voltage drop across each dielectric separately and then add them together. For a more complex capacitor with multiple dielectrics, it can be broken down into simpler components, such as two capacitors in parallel or in series.
Gabry89

## Homework Statement

A parallel plane capacitor with conducting plates area $$\Sigma$$= 400cm2, distant d=5mm, is half filled of mica (k1=5) and half filled of paraffin (k2=2). Calculate:

a) C (Capacitance of the capacitor)

...others

None

## The Attempt at a Solution

I haven't got too many problems solving this exercise but i just don't know how to get to the correct result of k (relative dielectric constant) when there's more than one dielectric in a parallel plate capacitor.

Calculate the voltage drop across the two dielectrics separately. Their sum will equal the voltage drop across the capacitor.

Ok, then:

V=(E*d)/k ; V1=(E*(d/2))/k1; V2=(E*(d/2))/k2;

V=V1+V2;

(E*d)/k=((E*d)*(k1+k2))/(2k1k2)

k=(2k1k2)/(k1+k2)

this should be correct thanks.

-------------------------------------------------------

Another question: if i would have had a capacitor like this:

i can't find k like i did before 'cause k would be like (k1*k2)/k1+k2 while it should be like
(k1+k2)/2

Last edited:
You can think of it as two capacitors in parallel.

ok, thanks i got it now, the sum of the capacitances of the two capacitors (cause they are in parallel) gives me the total capacitance.

So, in the first exercise I've asked you, the capacitors can be considered as connected in series?

Yes, effectively it's two capacitors in series.

vela said:
Yes, effectively it's two capacitors in series.

ok, thank you very much.

## 1. What is relative dielectric constant?

Relative dielectric constant, also known as relative permittivity, is a measure of the ability of a material to store electrical energy in an electric field. It is the ratio of the electric flux density in a vacuum to the electric flux density in the material.

## 2. How does the presence of more than one dielectric in a capacitor affect its relative dielectric constant?

The presence of more than one dielectric in a capacitor can increase its relative dielectric constant. This is because the electric flux density is affected by the properties of each dielectric material, resulting in a higher overall relative dielectric constant.

## 3. What are some examples of materials with high relative dielectric constants?

Some examples of materials with high relative dielectric constants include ceramics, glass, and certain plastics. These materials are often used in capacitors to increase their ability to store electrical energy.

## 4. How is relative dielectric constant calculated?

Relative dielectric constant is calculated by dividing the capacitance of a capacitor with a dielectric material by the capacitance of the same capacitor with a vacuum as the dielectric material. This ratio is also known as the dielectric constant.

## 5. Why is relative dielectric constant important in capacitor design?

Relative dielectric constant is important in capacitor design because it affects the overall capacitance of the capacitor. A higher relative dielectric constant means a higher capacitance, which can lead to increased energy storage and improved performance in electronic devices.

• Introductory Physics Homework Help
Replies
6
Views
619
• Introductory Physics Homework Help
Replies
2
Views
806
• Introductory Physics Homework Help
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
3
Views
1K
• Introductory Physics Homework Help
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
9
Views
2K
• Introductory Physics Homework Help
Replies
20
Views
2K
• Introductory Physics Homework Help
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
17
Views
2K
• Introductory Physics Homework Help
Replies
10
Views
3K