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The Importance of Capacitance Formula in Engineering Applications

Capacitors are specially designed to store energy by holding opposite charges apart. These two-terminal devices are capable of storing energy. On the other hand, capacitance measures the ability of a capacitor to store energy.

The capacitance formula is needed to calculate capacitance. Also, there are various applications of the capacitance formula. This formula is applied in some engineering applications. Also, the capacitance formula is crucial in calculating some things related to capacitance.

What is Capacitance?

Capacitance refers to the capability of a circuit to absorb and store energy in an electrical charge form. Also, capacitance is an electrical property that determines how much energy is stored in a capacitor. The unit of capacitance is Farad (F).

Furthermore, capacitance is usually expressed electric charge’s ratio on each conductor to the possible difference between them. Farads (F) represent the capacitance value of a capacitor. This was named after an English physicist Michael Faraday.

A farad represents a large quantity of capacitance. The majority of household electrical appliances have capacitors that generate just a fraction of a farad often known as microfarad. Microfarad represents a thousandth of a farad while nanofarad is a unit of capacitance that represent a billionth of a farad. Picofarad represents a trillionth of a farad. To have a better understanding, the units of capacitance include;

Picofarad (pF) 1pF=1/1,000,000,000

Nanofarad (nF) 1nF=1/1,000,000,000

Microfarad (μF) 1μF=1/1,000,000

On the other hand, Supercapacitors are capable of storing large electrical charges. Supercapacitors feature high capacitance which is about 2kF. Also, these capacitors are capable of storing large amounts of energy. They provide advanced technological possibilities in applications such as regenerative braking in automobiles and electrical motors.

What are Capacitors?

Capacitors are electronic components that store are energy. They are usually available in a wide range of shapes and sizes. Furthermore, they comprise two plates of conducting material which is usually sandwiched between an insulator made of materials like glass, film, and ceramic. A capacitor can store electrical charge and electrical energy.

The insulator is an electronic component that enhances the charging capacity of a capacitor. It is also known as a dielectric. The aviation, automotive and marine industries sometimes refer to capacitors as condensers in the automotive, marine and aviation industries. The internal plates of the capacitor are usually wired to two outer terminals. You can plug these terminals into a circuit.

Furthermore, batteries and capacitors store energy. However, capacitors quickly discharge energy while batteries gradually release energy.

Generally, capacitors have two electrical conductors in which distance separates them. These electrical conductors can sometimes be called “electrodes.”However,  they are widely known as more correctly, “capacitor plates.”Also, if the space between capacitors is a vacuum, such a capacitor is referred to as a “vacuum capacitor.”

However, a dielectric usually fills up the space. The dielectric is simply an insulating material. Capacitance determines how much energy is stored in a capacitor. Capacitors serves various functions ranging from radio reception to filtering static and storage of energy in heart defibrillators. Commercial capacitors usually comprise two conducting parts which are close to one another but not in contact.

Most times, engineers use a dielectric is used between the two plates. The battery moves some amount of charge of magnitude Q to the negative plate when you connect battery terminals to an initially uncharged capacitor.

How Do Capacitors Work?


To have a better understanding of how capacitors work, we will need to take the most basic structure of a capacitor into consideration.  Parallel plate capacitor can be described as the most basic structure of a capacitor. It comprises two parallel plates in which a dielectric separates them.

One plate (plate I) connects to the positive end while the other plate (Plate II) connects to the negative end when a DC voltage source is connected across the capacitor. The plate I is positive in respect to the second plate when you apply the battery potential across the capacitor. At this point, the current attempts to pass through the capacitor from its positive plate to its negative plate. However, it cannot pass through since an insulating material is separating the plates.

There is an electric field across the capacitor. Plate I will store positive charges from the battery while the plate II which connects to the negative end stores negative charges from the battery.  At a point in time, the capacitor will absorb the highest amount of charge as regards its capacitance in accordance to this voltage. This time span is usually referred to as the capacitor’s charging time.

The two plates will hold a positive and negative charge for a particular period when you remove the battery from the capacitor. Therefore, the capacitor functions as a source of electrical energy.

What are the Functions of Capacitors?

Capacitors serve various functions. Therefore, they are widely used in various applications and circuits like preventing the flow of DC current while allowing the transmission of audio signals, pulses, or other time different wave forms. The ability of capacitors to prevent the flow of DC currents makes capacitors ideal for smoothing out the output voltages of power supplies.

Also, capacitors can get rid of unwanted spikes that are in signals which could cause damage to components. These unwanted spikes could result in false triggering of digital components. Capacitors can as well help in adjusting an audio circuits’ frequency response. These components can couple together individual amplifier stages that need protection from DC current’s transmission.

A capacitor features infinite impedance when integrated on DC supplies. However, it features no impedance when integrated at extremely high frequencies. Also, it is important to know that all capacitors feature a maximum working DC voltage rating. Therefore, ensure you select a capacitor that has a higher voltage rating than the supply voltage.

Capacitors function as sensors. In this case, they measure various things which include fuel levels, humidity, and mechanical strain. Furthermore, capacitors condition power supplies. They enable the flow of AC signals when charged, thereby, preventing the flow of DC signals. A capacitor helps to decouple different parts of a circuit. This helps to minimize noise due to increasing efficiency. In utility substations, capacitors play a crucial role as they counteract inductive loading caused by transmission lines.

Capacitor Formula

Capacitors have many equations and calculation. To get the value of capacitance, you need to know the capacitor formula. The capacitor reactance equations are very common. However, you need to perform more capacitor calculations.

Capacitor calculations and capacitor equation have several aspects of capacitor operation. This includes the capacitance reactance calculations, capacitor charge, and more. The basic capacitor equation or capacitor formula is very useful in several areas of electronic circuit design. These calculations may seem useful only for theoretical purposes, but these calculations can also be useful in practical scenarios.

What is the Basic Capacitance Formula?

Capacitors in Series

Basic capacitor equations connect the capacitance with the charge the capacitor is holding. Capacitance is simply the capability of an electronic component to absorb and store energy in the form of an electrical charge. Also, it is how much electric charge a conductor can store for a defined difference in electric potential.

The basic equation for capacitance is C=Q/V

In this equation:

  • C represents capacitance in Farads
  • Q represents the charge on the plates
  • V represents the possible difference across the plates

It is crucial to always know the basic equation for capacitance. This is because it is usually integrated in a wide range of electrical circuit design. You can always remember this equation by using a memory triangle.

How to Calculate Capacitance of a Parallel Plate Capacitor

The calculation of the capacitance of a parallel plate capacitor is another basic calculations associated with capacitance. With the formula that was earlier given, you can predict the capacitance of a capacitor based on the area of the plates or the dielectric constant (Dk) between the two plates.

You can understand the levels of stray capacitance on PCBs and other aspects of electronic circuit design by using this basic theory and equation. As the speeds on electronic circuits keep rising fast as the technology for ICs , the levels of stray capacitance of the tracks increases and this can have a significant impact on the operation of the circuit. Therefore, it is important to take this factor into account for many circuit designs.

We can deduce capacitance equation below;

C=εr  ε0  A/d


 C is the capacitance

εr  is the relative permittivity for that medium

ε0  is the permittivity of space

A is the area of one plate

d is the distance between two plates

It is important to calculate the capacitance of a plate capacitor where you need to make use of flat capacitors. However, it is crucial to calculate the capacitance for a tubular capacitor.

How to Calculate the amount of Energy Stored in a Capacitor

Calculating the energy stored in a capacitor is another crucial equation related with capacitors. The amount of energy in the capacitors equals the work needed to pace the charge in a capacitor.

The energy stored in a capacitor is calculated using the formula;

W=∫Q0V dQ 

W=∫Q0qC dQ 


These formulae are important to determine the charge level in a capacitor. They are widely used in several areas of electronic circuit design. Also, calculating the amount of energy stored in a capacitor can be very useful in various scenarios like power supply design.

The capacitance equation helps in calculating the levels if capacitance and as well as the stored energy in them.

Voltage Rating in Capacitors

There is a maximum voltage rating in all capacitors. Therefore, you need to consider the amount of voltage applied to the capacitor when selecting a capacitor. The highest amount of voltage you can apply to the capacitor without any form of damage to its dielectric material is given as: WV DC, (DC working voltage).

There will be a breakdown in the dielectric if high voltage is applied across the capacitor. This is usually referred to as electrical breakdown. The breakdown will result in arcing between the capacitor plates and as such there is a short-circuit. The thickness of the dielectric material and the type of dielectric material determine the capacitor’s working voltage.

Dielectric leakage is another crucial factor that has a direct impact on the operation of a capacitor. Also, dielectric leakage occurs when an unwanted leakage current moves through the dielectric material. It is usually assumed that the dielectric’s resistance is very high and the dielectric is a good insulator that prevents the flow of DC current via the capacitor from one plate to another.

If excessive temperature or voltage causes a damage to the dielectric material becomes, this will result in a high leakage current flowing through the dielectric. Therefore, this makes the plates to loose charge quickly and also an overheating of the capacitor which causes the capacitor to have premature failure in the long run. Avoid using a capacitor in a circuit whose voltages are higher than the capacitor it is rated for. Otherwise, the capacitor may explode due to overheating.

Frequently Asked Questions

What is a variable capacitor?

The capacitance of a variable capacitor can vary to a particular range of values depending on necessity. A variable capacitor has two plates in which these plates are made of metals. One of the plates is movable while the other is fixed.

What type of energy does a capacitor store?

Electrical potential energy is the energy stored in a capacitor, which is related to the voltage V and charge Q on the capacitor.

How do you calculate the capacitance of a spherical capacitor?

A spherical capacitor comprises concentric conducting spherical shells of Radii R1 and R2. R1 has +Q while R2 has –Q charges. The electric field between these shells are radially outward.

The capacitance formula of a spherical capacitor is


With this capacitance equation, you can calculate the capacitance of a spherical capacitor.


A capacitor features infinite impedance when integrated on DC supplies. However, it features no impedance when integrated at extremely high frequencies. Capacitance is an electrical property that determines how much energy is stored in a capacitor. The unit of capacitance is Farad (F).




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