Dialectric inserted into capacitor => creation of a double-capacitor

In summary, the dialectic of width d is inserted into a capacitor made up of two plates, with the plates being a distance D apart. D>d. Afterwards, the capacitor acts like it is two capacitor connected in series. Why? I mean how the heck is the dialectic supposed to get induced charges equivalent to the ones on the capacitor-plates?The situation is illustrated in the solution manual. Look for assignment 4b ("Oppgave 4 b", page 4) http://folk.ntnu.no/sveinoll/ov/TFY/4155%20Elektrisitet%20og%20Elektromagnetisme/V11/LF/
  • #1
Nikitin
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A dialectic of width d is inserted into a capacitor made up of two plates, with the plates being a distance D apart. D>d. Afterwards, the capacitor acts like it is two capacitor connected in series. Why? I mean how the heck is the dialectic supposed to get induced charges equivalent to the ones on the capacitor-plates?

the situation is illustrated in the solution manual. Look for assignment 4b ("Oppgave 4 b", page 4) http://folk.ntnu.no/sveinoll/ov/TFY/4155%20Elektrisitet%20og%20Elektromagnetisme/V11/LF/Ov06los.pdf [Broken]. The situation as described is like A, and the capacitor acts like in B.
 
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  • #2


I mean how the heck is the dialectic supposed to get induced charges equivalent to the ones on the capacitor-plates?
It is not, why do you expect this?

You can imagine adding an additional conducting plate of "0" thickness between the dielectric and the air (or whatever) without changing the capacity. But then you just have two different capacitors in series.
This is possible without dielectric, too, by the way.
 
  • #3


A dialectric in series has equal charges on all the plates. Why doesn't this dialectric have that?
 
  • #4


I'm not 100% certain what your question is. But putting a dielectric in-between the plates causes the permittivity in-between the plates to change. And this means that the capacity of the capacitor will change. So by selecting a material of a certain permittivity, you can choose the capacitance of the capacitor. pretty neat.
 
  • #5


With or without a layer of metal between the dielectric and the air, I think the same situation exists. There will be a potential gradient across the air gap and a different (shallower) potential gradient across the dielectric because the molecules of the dielectric can polarise. It's just like two capacitors in series, sharing the total PD. The equivalent capacitance will be greater than for an air gap and less than when full of dielectric.
 
  • #6


Nikitin said:
A dialectric in series has equal charges on all the plates. Why doesn't this dialectric have that?

its spelt ... Dielectric :)

It seems you don't realize or understand what a dielectric is
its the non-conductive layer between 2 plates of a capacitor
it may be composed of air, paper or ceramic amongst other things

The thickness and composition of which, as others have said, will have an effect on the value of capacitance


Dave
 

1. What is a dielectric material?

A dielectric material is an insulating substance that can store electrical energy by polarizing in an electric field. It is commonly used in capacitors to increase their capacitance.

2. How does a dielectric inserted into a capacitor create a double-capacitor?

When a dielectric material is inserted into a capacitor, it increases the capacitance by reducing the electric field between the plates. This allows more charge to be stored on the plates, effectively creating a double-capacitor with a higher capacitance than before.

3. What are the benefits of using a double-capacitor?

A double-capacitor has a higher capacitance than a single capacitor, which allows it to store more energy. This makes it useful in applications where a higher energy storage capacity is required, such as in electronic devices.

4. Can any dielectric material be used in a capacitor?

No, not all dielectric materials are suitable for use in capacitors. The material must have a high dielectric constant and be able to withstand high electric fields without breaking down. Common dielectric materials used in capacitors include ceramic, paper, and plastic.

5. What factors affect the capacitance of a double-capacitor?

The capacitance of a double-capacitor is affected by the material and size of the capacitor plates, the distance between the plates, and the type of dielectric material used. It is also influenced by the voltage applied to the capacitor and the temperature of the surrounding environment.

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