Capacitors, Capacitance and Dielectrics

In summary, parallel-plate capacitors are made up of two parallel plates with opposite polarities and a distance d between them. The purpose of a capacitor is to store potential energy, which is done by doing work to establish the distance between the plates. A dielectric can increase the capacitance of a capacitor but also decreases the stored potential energy. However, the value of capacitance alone does not determine the amount of energy stored in a capacitor. Other equations, such as Energy = 0.5CV2, show that energy can also be proportional to the capacitance.
  • #1
Peter G.
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Hi,

So I am learning about parallel-plate capacitors.

The way my book puts it is that it is basically two parallel plates of opposite polarities, separated by a distance d. In order to establish that distance, work must be done and the energy is stored as electric potential energy.

From that description, I understand that the purpose of a capacitor is to store potential energy.

I then learn that a dielectric can increase the capacitance of a capacitor by decreasing the potential difference but, in the process, it diminishes the stored potential energy, according to the equation:

Energy = Q2/C

Why, then, is a dielectric used if it decreases the potential energy (what I thought as the function of the capacitor)? The purpose of a capacitor is to store more charge? There must be a connection I am not seeing. :redface:

Can anyone elucidate me?

Thanks!
 
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  • #2

Related to Capacitors, Capacitance and Dielectrics

1. What is a capacitor and how does it work?

A capacitor is an electronic component that stores electrical energy in an electric field. It is made up of two conductive plates separated by a dielectric material. When a voltage is applied to the plates, one plate becomes positively charged and the other becomes negatively charged, creating an electric field between them. This electric field stores the energy in the capacitor.

2. What is capacitance and how is it measured?

Capacitance is a measure of a capacitor's ability to store electrical energy. It is measured in farads (F) and is calculated by dividing the amount of charge on one plate by the voltage difference between the plates. Capacitance can also be affected by the physical characteristics of the capacitor, such as the distance between the plates, the size of the plates, and the type of dielectric material used.

3. What are some common applications of capacitors?

Capacitors have many different uses in electronic circuits. They are commonly used in power supplies to filter out noise and provide a steady DC voltage. They are also used in audio circuits to block certain frequencies and in timing circuits to control the frequency of oscillations. Capacitors are also used in electric motors, flash photography, and many other electronic devices.

4. What is a dielectric and how does it affect capacitance?

A dielectric is an insulating material that is placed between the two conductive plates of a capacitor. It is used to increase the capacitance of the capacitor by reducing the electric field between the plates. The type of dielectric used can affect the capacitance of a capacitor, with some materials having a higher dielectric constant and thus increasing the capacitance.

5. Can capacitors store an infinite amount of charge?

No, capacitors have a maximum capacitance and can only store a finite amount of charge. The maximum capacitance is determined by the physical characteristics of the capacitor, such as the size of the plates and the type of dielectric material used. Additionally, capacitors have a breakdown voltage, which is the maximum voltage that can be applied before the dielectric breaks down and the capacitor becomes damaged.

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