# Capacitance from plates

• Krushnaraj Pandya
In summary, the conversation discusses finding the equivalent capacitance between plates A and B with a distance d between them, given that there are five plates with the same area. The answer is given as 5C/3 in terms of C, and a suggestion is made to draw an equivalent circuit with four capacitors. The top and fourth plates are connected and labeled as node C.

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## Homework Statement

Five plates with same area are placed as in figure. Distance between any 2 consecutive plates is d. Find equivalent capacitance(ab). (Note-Answer is given as 5C/3, in terms of C so I suppose C is capacitance of a +ve and -ve plate separated by d). The lower letter is A, it is marked positive and upper letter is B marked negative.

All related.

## The Attempt at a Solution

numbering 1 to 5 from top to bottom. I can see 1 capacitor due to negative 2 and positive 3 and none else since 1 and 4 are uncharged so answer should be C...unless charges get induced. In that case there are 4 capacitors and answer should be 4C. I'd be grateful for some help.

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e-pie said:
I only have a inbuilt webcam...please pardon the poor quality. I'll post another one however, I've provided all information and the general outline of the figure should be enough...

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Try drawing an equivalent circuit. It should have four capacitors on it, one per gap.

The top plate and forth plate are connected together. I recommend labeling that connection node C.

Krushnaraj Pandya
CWatters said:
Try drawing an equivalent circuit. It should have four capacitors on it, one per gap.

The top plate and forth plate are connected together. I recommend labeling that connection node C.
Got it! That was very neat. Thank you very much for your help.

## 1. What is capacitance?

Capacitance is the ability of a system to store an electric charge. It is measured in farads (F) and represents the ratio of the stored charge to the potential difference between the plates of a capacitor.

## 2. How is capacitance calculated?

Capacitance is calculated by dividing the charge (Q) by the potential difference (V) between the plates of a capacitor. It can also be calculated by multiplying the permittivity of the material (ε) by the area of the plates (A) and dividing by the distance between the plates (d).

## 3. What factors affect capacitance?

The capacitance of a capacitor is affected by the distance between the plates, the area of the plates, and the permittivity of the material between the plates. It is also affected by the type of dielectric material used and the number of plates in the capacitor.

## 4. How does capacitance affect the energy stored in a capacitor?

The energy stored in a capacitor is directly proportional to the capacitance. This means that as capacitance increases, so does the amount of energy that can be stored in the capacitor. This relationship is described by the equation E = 1/2CV², where C is the capacitance and V is the potential difference between the plates.

## 5. How is capacitance used in practical applications?

Capacitors are used in a variety of practical applications, such as in electronic circuits for energy storage and filtering, in power factor correction for improving the efficiency of electrical systems, and in sensors for measuring physical properties such as humidity and pressure. They are also used in power supplies, audio equipment, and many other devices.