# About Electrostatic Forces on Parallel Plate Capacitor

• hanley93
In summary, the conversation discusses the concept of parallel plate capacitors and how people maintain the distance between the plates to prevent them from touching. This is achieved by using a solid or liquid dielectric material between the plates. Additionally, the potential difference is maintained as long as the charge remains on the plates. Variable capacitors allow for changes in the capacitance and therefore the potential difference.
hanley93

In parallel plate capacitor, we charge the capacitor by connecting a power supply/battery. Then, after few minutes, the capacitor is fully charged with different signs, + and -. With that difference in signs, there must be forces, same magnitude, acting on both plates which draw them closer. What I want to ask is, how do people maintain the distance between the plates? I mean, there are attractive forces, so, there must be another force with different direction right? If not, then the plates will be accelerated toward each other.

I am confused by this. Many lectures I've watched never talk about electrostatic forces again after they get to parallel plate capacitor.

Ah, another one, how do people maintain potential difference? Doesn't the same problem apply? I just haven't fully understood the concept of voltage yet. Because voltage is generated by point charge and then suddenly it is there by itself, can someone explains to me?

Last edited:
hanley93 said:
how do people maintain the distance between the plates?

Real capacitors usually have some kind of solid material (called a "dielectric") between the plates. Sometimes the dielectric is liquid, in which case the plates have to be rigid enough to withstand the attractive force between them.

jtbell said:
Real capacitors usually have some kind of solid material (called a "dielectric") between the plates. Sometimes the dielectric is liquid, in which case the plates have to be rigid enough to withstand the attractive force between them.

Thanks for the answer, so the dielectric is used to keep the distance so that the plates won't touch each other right?

"the plates have to be rigid enough to withstand the attractive force between them", is there any normal forces that help this process?

The force between the plates is pretty small anyway and for fixed value capacitors it is the mechanical structure,including any dielectrics etc as mentioned by jtbell,that maintains the separation.
The potential difference is proportional to the charge build up on the plates and is maintained as long as the charge remains.If the charge leaks away the pd drops.
There are variable capacitors where either the overlap plate area can be changed or the plate separation changed.When these are charged and disconnected from the circuit then changing the capacitance changes the pd.

The force between the plates is pretty small anyway and for fixed value capacitors it is the mechanical structure,including any dielectrics etc as mentioned by jtbell,that maintains the separation.
The potential difference is proportional to the charge build up on the plates and is maintained as long as the charge remains.If the charge leaks away the pd drops.
There are variable capacitors where either the overlap plate area can be changed or the plate separation changed.When these are charged and disconnected from the circuit then changing the capacitance changes the pd.

Ah got it now, thank you! thank you!

## 1. What is a parallel plate capacitor?

A parallel plate capacitor is a device that stores electrical energy by creating an electric field between two parallel conductive plates. It consists of two plates made of a conducting material, separated by a dielectric material, and connected to a power source.

## 2. How do electrostatic forces work in a parallel plate capacitor?

Electrostatic forces occur between charged particles, such as the electrons and protons in an atom. In a parallel plate capacitor, when a voltage is applied to the plates, one plate becomes positively charged and the other becomes negatively charged. This creates an electric field between the plates, causing electrostatic forces to act on any charged particles in the vicinity.

## 3. What factors affect the strength of electrostatic forces in a parallel plate capacitor?

The strength of electrostatic forces in a parallel plate capacitor depends on the distance between the plates, the amount of charge on each plate, and the type of dielectric material used. The closer the plates are together, the stronger the electric field and therefore, the stronger the electrostatic forces. Similarly, the greater the charge on the plates, the stronger the forces. The type of dielectric material used can also affect the strength of the forces, as some materials have a higher dielectric constant than others.

## 4. How is the capacitance of a parallel plate capacitor calculated?

The capacitance of a parallel plate capacitor is calculated using the formula C = εA/d, where C is the capacitance, ε is the permittivity of the dielectric material, A is the area of the plates, and d is the distance between the plates. This formula shows that the capacitance is directly proportional to the area of the plates and inversely proportional to the distance between them.

## 5. What are some practical applications of parallel plate capacitors?

Parallel plate capacitors are commonly used in electronic circuits to store and regulate electrical energy. They are also used in various types of sensors, such as accelerometers and touch screens, and in high voltage equipment, such as power supplies and particle accelerators. Additionally, parallel plate capacitors are used in the production of electrolytic capacitors, which are widely used in consumer electronics.

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