Capacitor and Capacitance | Definition, Types and Applications

Capacitors are known for their ability to store and release electrical energy. In this article, we will explore what are capacitors and its difinition, what capacitance means, and the difference between Capacitor and Capacitance. Capacitors and capacitance are intricately linked, as capacitance essentially represents the capacity of a capacitor to hold an electric charge. Capacitors, crucial elements in electronic circuits, function as storage units for electrical energy in the form of a charge. Their widespread application spans power supplies, filtering circuits, timing circuits, and coupling circuits. In this article we will also discuss the applications of capacitors, type of Capacitor and How Capacitors Work.

A capacitor’s capacitance, an important statistic, quantifies its ability to store electrical energy. It denotes the amount of charge that the capacitor can hold per unit of applied voltage. Individuals working in electrical circuitry or those interested in the subject of electronics need to understand the fundamental ideas around capacitors and capacitance.

What is a Capacitor? | Definition of Capacitor

Definition of  Capacitor

– A capacitor is an electronic component that stores and releases electrical energy. It consists of two conductive plates separated by an insulating material known as a dielectric. When a voltage is applied across the plates, an electric field is created, causing charge to accumulate on the plates. The amount of charge that a capacitor can store is determined by its capacitance. The capacitance of a capacitor is directly proportional to the surface area of its plates, inversely proportional to the distance between them, and also influenced by the dielectric constant of the material separating the plates.

On a larger scale, capacitors feature prominently in the power supplies of various electronic devices, including computers and peripherals. In these systems, capacitors play a vital role in smoothing out rectified utility AC, ensuring a steady and battery-like supply of DC power. The diverse uses of capacitors underscore their significance in both miniaturized integrated circuits and larger-scale electronic systems.

PCB Capacitors

A PCB capacitor is a two-terminal electrical component that stores electric charges and enables the flow of alternating current (AC). Capacitors, like resistors and inductors, are fundamental passive components found in a wide range of circuits. When it comes to the amount of components on a circuit board, it is second only to resistors.

It is necessary to note that when we mention PCB capacitors in this article, we are referring to the Printed Circuit Board capacitors that are commonly used these days, not to be confused with PCB (Polychlorinated Biphenyls Capacitors), which has been prohibited in some countries.

Please read this article for the details: PCB Capacitors: Why Is It Important and How to Choose?

What is Capacitance?

Capacitance is the property of a capacitor that determines its ability to store charge. It is a measure of how much charge a capacitor can hold per unit of voltage. The unit of capacitance is the farad (F), named after the physicist Michael Faraday. However, farads are typically too large for most electronic applications, so capacitors are usually measured in microfarads (μF), nanofarads (nF), or picofarads (pF).

Capacitance is measured in farads (F), with more practical units including the microfarad (µF) and picofarad (pF). Capacitors find applications in integrated circuit (IC) chips, notably in dynamic random access memory (DRAM) alongside transistors. Here, capacitors play a crucial role in preserving memory content, necessitating rapid recharging to prevent data loss.

Difference between Capacitor and Capacitance

The main difference between a capacitor and capacitance lies in their definitions. A capacitor is a physical electronic component, while capacitance is a property of that component. In other words, a capacitor is the actual device that stores and releases electrical energy, whereas capacitance refers to the amount of charge that the capacitor can store.

Another way to understand the difference is to think of capacitance as the capacity of a capacitor. It is similar to how a bucket has a certain capacity to hold water. The bucket is the capacitor, while the capacity is the capacitance.

Capacitance is the effect of the capacitor. Capacitance is defined as the ratio of electric charge Q to the voltage V and it is expressed as

C = Q/V


  • Q is the electric charge measured in coulombs
  • C is the capacitance measured in farad
  • V is the voltage across the plates measured in volts

How Capacitors Work

A capacitor is similar to a battery. Capacitors and batteries both store electrical energy, but in very different ways. You are aware that the battery has two connections. When you make a circuit inside the battery, chemical reactions produce electrons on one terminal and absorb them on the other. A capacitor is significantly simpler than a battery because it does not generate new electrons but merely stores them. A capacitor gets its name from its “capacity” to store energy.

The terminals of a capacitor connect to two metal plates separated by a non-conducting material, or dielectric. the dielectric can be any non-conductive substance. Some specific materials are used that best suit the capacitor’s function. Non-conductive materials include mica, ceramic, cellulose, porcelain, Mylar, Teflon, and even air. The dielectric determines what type of capacitor it is and for what applications it is best suited. Some capacitors are better suited for high-frequency applications, while some are better for high-voltage applications, depending on the size and kind of dielectric.

Capacitor Circuit

Here’s what happens when you connect a capacitor to a battery:

  • The plate on the capacitor that connects to the battery’s negative terminal absorbs electrons produced by the battery.
  • The plate on the capacitor that connects to the battery’s positive terminal loses electrons to the battery.

The capacitor has the same voltage as the battery once it has been charged (1.5 volts on the battery equals 1.5 volts on the capacitor). The capacity of a tiny capacitor is low. Large capacitors, on the other hand, can hold a lot of charge. Capacitors the size of soda cans can contain enough charge to light a flashlight for a minute or longer.

Even nature, in the form of lightning, demonstrates the capacitor at operation. The cloud represents one plate, the ground is another, and the lightning is the charge that is released between these two “plates.” Obviously, a capacitor of that size can carry a massive charge!

how capacitor work

How Are Capacitors Classified?

According to structure, classification of Capacitors are as follows:Fixed Capacitors

Fixed capacitors are electronic components that store electrical energy in an electric field. They consist of two conductive plates separated by an insulator called a dielectric. The value of capacitance is fixed during manufacturing and cannot be changed.

Variable Capacitors

Variable capacitors, also known as tuning capacitors or variable trimmers, are electronic components that allow the capacitance value to be adjusted manually. This is achieved by varying the distance between the two conductive plates or the area of overlap between them.

Trimmer Capacitors

Trimmer capacitors are a special type of variable capacitor that is designed for fine adjustment of capacitance. They are typically small and have a limited range of adjustment. Trimmer capacitors are often used to calibrate circuits after they have been assembled.

The capacitors are classified into two types according to polarization:

What is polarized capacitor?

A polarized capacitor is a type of capacitor that has a positive and a negative terminal. Unlike non-polarized capacitors, which can be connected in either direction, polarized capacitors must be connected with the correct polarity. If connected incorrectly, the capacitor can be damaged or even explode. Polarized capacitors typically use electrolytic or tantalum dielectrics. These dielectrics are formed by a thin layer of oxide on the surface of the anode (positive terminal). These capacitors are used to achieve high capacitive density.

What is Unpolarized capacitors?

Unpolarized capacitors, also known as non-polarized capacitors, are electronic components designed to store and release electrical energy without a specific orientation. Unlike polarized capacitors such as electrolytic capacitors, which have a positive and a negative terminal, unpolarized capacitors lack a predefined polarity. This makes them suitable for use in AC (alternating current) circuits where the voltage periodically changes direction. Unpolarized capacitors come in various types, including ceramic capacitors and film capacitors, and find applications in audio circuits, coupling and decoupling circuits, and other instances where a non-directional capacitance is required. Their versatility and ability to handle AC signals make them valuable in a wide range of electronic devices and systems.

After understanding the classification of capacitors, let us learn about capacitor types. So we are going to discuss some common types of Capacitors.

Types of Capacitors

There are various types of capacitors available, each with its own characteristics and applications. Some of the common types of Capacitors are as follows:

Ceramic capacitors:

A ceramic capacitor is one of the most prevalent types of capacitors. This capacitor type is made of dielectric material. Ceramic capacitors are also non-polar, which means they can be utilized in any direction in a circuit.

Electrolytic capacitors:

Electrolytic capacitors are electronic components commonly used for energy storage in circuits. They feature a unique construction with an electrolyte, typically a liquid or gel, that enhances their capacitance. The two primary types are aluminum electrolytic capacitors and tantalum electrolytic capacitors, each with distinct characteristics. Due to their polarity, it is crucial to observe proper orientation during installation, as reversing the voltage can lead to capacitor failure or even damage. Electrolytic capacitors find widespread use in power supply circuits and applications where high capacitance values are essential for smoothing voltage and ensuring stable operation.

Tantalum capacitors:

Tantalum capacitors are a type of electrolytic capacitor known for their high capacitance values and compact size. They utilize tantalum metal as the anode material, which allows for a thin dielectric layer, resulting in a higher volumetric efficiency compared to other electrolytic capacitors. Tantalum capacitors are often used in electronic devices where space is a critical factor, and their stable capacitance makes them suitable for applications requiring reliable and long-term performance.

Film capacitors:

Film capacitors are a type of electronic component used for storing and releasing electrical energy. They are characterized by a dielectric film that separates the capacitor’s conductive layers. This dielectric film can be made from materials such as polyester, polypropylene, or polycarbonate, contributing to the capacitor’s stability and reliability. Film capacitors are commonly employed in various applications, including filtering, coupling, and smoothing circuits in electronic devices and systems.

Variable capacitors:

Variable capacitors, also known as tuning capacitors, are unique components that allow you to adjust their capacitance within a specific range. This ability to “tune” their electrical properties makes them essential for many electronic applications.

These are some capacitor types. We can used different capacitors for different application. Do you know “Which capacitor used in ceiling fan?” Answer is “The capacitor used in a ceiling fan is a non-polarized electrolytic AC capacitor”.

Applications of Capacitors

Capacitors have a wide range of applications in various industries. They store electrical energy in an electric field and can release it when needed. This unique property allows them to be used in a wide variety of applications. Some of the common applications are as follows:

Energy storage:

  • Electronics: Capacitors are used to store short-term energy in electronic devices, such as computers, smartphones, and cameras. This allows the devices to function properly even when the power supply is interrupted momentarily.
  • Uninterruptible power supplies (UPS): Large capacitors are used in UPS systems to provide backup power during outages. This ensures that critical equipment, such as computers and servers, can continue to operate uninterrupted.
  • Defibrillators: Capacitors store the electrical energy needed to shock a patient’s heart back into rhythm in the event of a cardiac arrest.

Power conditioning:

  • Power factor correction: Capacitors are used to improve the power factor of electrical loads. This reduces the amount of current drawn from the power supply, which can improve efficiency and reduce energy costs.
  • Smoothing power supplies: Capacitors are used to smooth out the voltage output of power supplies. This is especially important for sensitive electronic devices that require a steady voltage supply.
  • Voltage regulation: Capacitors can be used to regulate the voltage output of a power supply. This is done by using a capacitor in conjunction with a voltage regulator circuit.

Signal processing:

  • Filters: Capacitors are used in filters to block unwanted frequencies from an electrical signal. This is important for applications such as audio and radio where it is necessary to separate different signals.
  • Tuning circuits: Capacitors are used in tuning circuits to select a specific frequency from a radio signal. This allows you to tune your radio to a particular station.
  • Coupling and decoupling: Capacitors are used to couple and decouple circuits. This allows you to transfer signals between circuits without interfering with the operation of other circuits.

Other applications:

  • Motor starters: Capacitors are used to start electric motors. They provide the initial surge of current needed to get the motor spinning.
  • Sensing: Capacitors can be used to sense changes in physical parameters, such as pressure, temperature, and humidity. This is done by measuring the change in capacitance caused by the change in the physical parameter.
  • Weapons: Capacitors are used in some weapons to store the energy needed to fire a projectile.

These are only a few of the many uses for capacitors. They play critical roles in a wide range of electronic devices and systems. As technology advances, we can anticipate even more creative applications for capacitors in the future.

Timing circuits:

Timing circuits are widely used in various electronic devices, including oscillators, timers, and clocks. Capacitors play a crucial role in these circuits by controlling the timing intervals and ensuring accurate and precise timekeeping.

Noise filtering:

Noise, in the context of electronic circuits, refers to unwanted electrical signals that can interfere with the proper functioning of devices. Capacitors are commonly used for noise filtering purposes, helping to eliminate or reduce undesirable noise from power supplies and signal lines.

Recommended: Please read this article “The Role of Capacitors in Timing Circuits and Noise Filtering“for find more details about the role of Capacitors in Timing circuits and Noise filtering.


Are capacitor and conductor the same?

It is an electrical device, which store electricity in the form of electrostatic charges or Any two metallic plates, separated by a di-electric (Insulator) constitute a capacitor or condenser. An electrical conductor is a substance in which electrical charge carries, usually electrons move easily from atom to atom with the application of voltage.

Can capacitor reduce electricity bill?

No, it does not. For the bill, the meters read actual power. The capacitors are used to restore the current and voltage to their original phases, allowing the meter to read more genuine power.

Which capacitor used in ceiling fan?

The capacitor used in a ceiling fan is a non-polarized electrolytic AC capacitor.

Why capacitor blocks dc?

DC current no longer flows through the capacitor once the power source has fully charged it. Because the electrode plates of the capacitor are separated by an insulator (air or a dielectric), no DC current can flow unless the insulation dissolves.

What is symbol of Capacitor? | Capacitor Symbol

Capacitor Symbol


Capacitors and capacitance are fundamental concepts in the world of electronics. Capacitors store and release electrical energy, while capacitance determines their ability to store charge. Understanding these concepts and their applications is essential for anyone working with electronic circuits and systems.

By exploring the different types of capacitors, applications and its working, we can gain a deeper understanding of how these components contribute to the functionality of various electronic devices.

Harshvardhan Mishra

Hi, I'm Harshvardhan Mishra. Tech enthusiast and IT professional with a B.Tech in IT, PG Diploma in IoT from CDAC, and 6 years of industry experience. Founder of HVM Smart Solutions, blending technology for real-world solutions. As a passionate technical author, I simplify complex concepts for diverse audiences. Let's connect and explore the tech world together! If you want to help support me on my journey, consider sharing my articles, or Buy me a Coffee! Thank you for reading my blog! Happy learning! Linkedin

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