# The behaviour of an uncharged dielectric particle in a capacitor

• kololo
In summary, the conversation discusses the effects of polarisation on a dielectric particle placed between parallel plate electrodes. It is established that the particle, being similar to an insulator, will not be charged. However, when the particle is placed off-center, there will be a net force acting on it due to the distribution of surface charges and electric field lines. Further resources are recommended to gain a better understanding of the topic.
kololo
Homework Statement
What happens to an uncharged particle with a dielectric constant (lower conductivity) when it is placed in a pair of parallel plate electrodes (charged)?
Relevant Equations
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I understand that the particle will be polarised according to its dielectric constant and the electric field across the capacitor.
However, since it is similar to an insulator and electrons do not move in and out of the particle easily, the particle will not be charged.
How then will polarisation cause the particle to move in a pair of parallel plate electrodes? Appreciate it if anyone could guide me/ direct me to any related books/ materials. I am a beginner in this topic, and have been looking through the internet but it's of little avail.

Did you make some sketches of the field and charge distributions?

Let the particle be a sphere of dielectric material. You might start with a sketch where the particle is placed precisely halfway between the charged parallel plates. What does the surface polarization charge distribution look like on the sphere? What does the surface charge distribution look like on each plate? (It won't be uniform.) Roughly, what does the pattern of electric field lines look like? Is there a net force on the particle in this case?

Now suppose the particle is not halfway between the plates. For example, let the particle be placed very close to the positive plate. Sketch the charge distributions and field lines. Can you see that there will now be a net force on the particle? What is the direction of the net force?

kololo
If you google "Dielectric sphere in a uniform electric field" you will find quite a bit of information including videos. It is a standard problem in electrostatics and is a standard solved example in most intermediate level E&M textbooks as an application of the Uniqueness theorem to boundary value problems.

The question is, what is your level? If you don't quite understand what I'm talking about in the paragraph above, then @TSny's approach is the way to proceed. On the surface of the particle, draw teeny-tiny polarized football-shaped atoms with a ##+## and a ##-## at the two ends, all oriented in the same direction (which direction should this be?), then see what you can say about the net force on the particle.

kololo

## 1. How does an uncharged dielectric particle behave in a capacitor?

The behaviour of an uncharged dielectric particle in a capacitor depends on the properties of the dielectric material and the electric field within the capacitor. Generally, the particle will align itself with the electric field, causing a redistribution of charges on the capacitor plates.

## 2. What is the role of a dielectric particle in a capacitor?

A dielectric particle is used in a capacitor to increase the capacitance, or the ability to store electric charge. The particle acts as an insulator, reducing the electric field between the capacitor plates and allowing for a higher charge to be stored.

## 3. How does the size of the dielectric particle affect its behaviour in a capacitor?

The size of the dielectric particle can affect its behaviour in a capacitor. Generally, larger particles will have a greater effect on the electric field and can lead to a higher capacitance. However, if the particle is too large, it may not fit between the capacitor plates and can cause a decrease in capacitance.

## 4. What is the difference between a polar and non-polar dielectric particle in a capacitor?

A polar dielectric particle has a permanent dipole moment, meaning it has a positive and negative charge separated by a small distance. This can enhance the effects of the electric field in a capacitor. Non-polar dielectric particles do not have a dipole moment and may have a smaller effect on the electric field.

## 5. How does the dielectric constant of a particle affect its behaviour in a capacitor?

The dielectric constant, also known as the relative permittivity, represents the ability of a material to store electric charge. A higher dielectric constant means the particle has a greater ability to reduce the electric field and increase the capacitance of the capacitor. Therefore, particles with higher dielectric constants will have a greater effect on the behaviour of a capacitor.

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