Capacitance of point charge electrode

In summary, a capacitor is a physical structure that holds point charges and the energy is based on the force between these charges. The capacitance of the system can be calculated by using the formula V=Q/C. However, in the case of a point charge being the upper electrode, the potential difference and capacitance will be 0 due to the infinite potential near the point charge. Therefore, this system cannot be considered a capacitor.
  • #1
shomey
30
0
Consider a capacitor which is just like a plate capacitor, but instead of the upper electrode being a plate it is a point charge Q. the lower plate is held at a fixed potential V=0.

how could you calculate the capacitance of the system?

when trying to calculate - it looks like it will be 0 since the potential near the point charge is inifinite and so is the potential difference between the two electrodes, and the C=Q/V is 0...
 
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  • #2
The energy of a capacitor is based on force between point charges. The physical structure that holds the charges is called a capacitor. As point charges are added to a capacitor, voltage increases (V=Q/C).

A point charge is neither a conductor, nor an insulator. A magnetic field cannot add kinetic energy to a point charge, but a (changing) magnetic field can add magnetism to a conductor. The electron environment makes a difference.

In other words, a point charge near a conductive plate is not a capacitor.
 
  • #3
pzlded said:
The energy of a capacitor is based on force between point charges. The physical structure that holds the charges is called a capacitor. As point charges are added to a capacitor, voltage increases (V=Q/C).

A point charge is neither a conductor, nor an insulator. A magnetic field cannot add kinetic energy to a point charge, but a (changing) magnetic field can add magnetism to a conductor. The electron environment makes a difference.

In other words, a point charge near a conductive plate is not a capacitor.

OK thanks.
I was asked to calculate the capacitance of such a system...
so you're saying that the question is problematic right?
 

1. What is the capacitance of a point charge electrode?

The capacitance of a point charge electrode is the ability of the electrode to store electric charge. It is a measure of the amount of charge that can be stored on the electrode for a given potential difference. It is typically measured in units of Farads (F).

2. How is the capacitance of a point charge electrode calculated?

The capacitance of a point charge electrode can be calculated using the formula C = Q/V, where C is the capacitance, Q is the charge on the electrode, and V is the potential difference between the electrode and its surroundings. This formula assumes that the electrode is a perfect conductor and that the charge is evenly distributed on its surface.

3. What factors affect the capacitance of a point charge electrode?

The capacitance of a point charge electrode is affected by several factors, including the distance between the electrode and its surroundings, the size and shape of the electrode, and the dielectric constant of the material between the electrode and its surroundings. Generally, a larger electrode or a smaller distance between the electrode and its surroundings will result in a higher capacitance.

4. How does the capacitance of a point charge electrode impact its performance?

The capacitance of a point charge electrode can impact its performance in several ways. A higher capacitance means that the electrode can store more charge, which can be beneficial in applications where the electrode needs to hold a large amount of charge. However, a high capacitance can also lead to a slower response time and increased energy consumption.

5. Can the capacitance of a point charge electrode be adjusted?

Yes, the capacitance of a point charge electrode can be adjusted by changing the factors that affect it, such as the distance between the electrode and its surroundings or the size and shape of the electrode. In some cases, a dielectric material may also be added between the electrode and its surroundings to increase the capacitance. However, the capacitance of a point charge electrode also depends on its design and materials, which cannot be easily changed.

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