What is a Capacitor and Different Types of Capacitors?
The capacitor is a device that has the ability or "power" to store energy in the form of an electrical charge that creates a potential difference (Static Voltage) through its plates, much like a small rechargeable battery. There are many types of capacitors available from very small capacitor beads that use resonance circuits to large power factor correction capacitors, but they all do the same, they store charge. In other words, the capacitor is an electronic component whose function is to store electrical charges. It is made of two conductors separated by a dielectric film. These plates accumulate electrical charges when connected to a power source.
They are often storage sites for analogue signals and digital data. In general, comparisons between the different types of capacitors are made concerning the dielectric used between the plates. Some capacitors look like tubes, small capacitors are often made from ceramic materials and then dipped into an epoxy resin to seal them. Below are some of the more common types of capacitors available.
Capacitor Types
The types of capacitors available range from very small, delicate trimming capacitors used in oscillators or radio circuits, to large-scale metal-type capacitors used in high-voltage power correction and smoothing circuits.
The comparison between the different types of capacitors is generally made concerning the dielectric used between the plates. Unlike resistors, there are also various types of capacitors that allow us to vary their capacitance value for use in radio or "frequency tuning" style circuits.
Some of the capacitors appear like tubes since the metal foil plates are rolled up into a circle to make a small bundle with the insulating dielectric layer sandwiched between them.
Small capacitors are often made from ceramic materials and then immersed in epoxy resins to seal them. Either way, capacitors play an important role in electronic circuits, so here are some of the more "common" types of capacitors available.
Applications of Capacitors
Capacitors have been used in both physical and electronic devices. They are used in filter applications, energy storage systems, engine starters, and signal processing equipment.
Four Types of Capacitors
Film Capacitors:
Film capacitors are the most widely prepared of a variety of types of capacitors, consisting of a relatively expansive category of capacitors defining their dielectric properties. They are available in almost any weight and voltages up to 1500 volts. They vary in any tolerance from 10% to 0.01%. In addition, film capacitors come in a variety of shapes and case types. There are two types of film capacitors, the type of radial lead and the type of axial lead. The film capacitor electrodes may be metallic aluminum or zinc, mounted on one or both sides of the plastic film, resulting in metallic film capacitors called film capacitors. The film capacitor is shown in the following figure:
Ceramic Capacitors:
Ceramic capacitors are used in high-frequency circuits such as RF audio. They are also the best alternative for high-frequency compensation for audio circuits. These capacitors are also called disk capacitors. Ceramic capacitors are made by coating two sides of small silver porcelain or ceramic disk and then stacked together to make a capacitor. Low capacitance and high capacitance in ceramic capacitors can be achieved by changing the thickness of the ceramic disk used.
Electrolytic Capacitors:
These are the most widely used capacitors with a wide tolerance capacity. Electrolytic capacitors are obtainable with working voltages of up to 500V, although high capacitance values are not accessible at high voltage and higher temperature units are not normal. Two types of electrolytic capacitors, Tantalum, and Aluminum are common. Electrolytic capacitors are categorized based on their dielectric.
Aluminum electrolytic capacitors – aluminum oxide ( dielectric).
Tantalum electrolytic capacitors – tantalum pentoxide (dielectric).
Niobium electrolytic capacitors – niobium pentoxide ( dielectric).
Variable Capacitors:
Among the different types of capacitors are a Variable Capacitor, which is one whose capacity can be changed mechanically intentionally, and repeatedly. This type of capacitor was used to set the resonance frequency in LC circuits, e.g. to adjust the radio for impedance matching in antenna tuner devices.
What are Common Capacitors?
Capacitors are mainly divided into two mechanical groups:
Fixed capacitors
Variable capacitors
Some common capacitors and their names are mentioned in the table below.
Capacitor Types and Use
The easiest design of the capacitor is the use of two parallel metal plates separated by an insulation layer called a dielectric.
How Capacitor Works
To begin, we can see that a metal contains an equal number of positively and negatively charged particles, indicating that it is electrically neutral. When we connect a power source or a battery to the capacitor's metal plates, a current or electrons will attempt to travel from the plate connected to the positive lead of the battery to the plate connected to the negative lead of the battery. However, because of the dielectric between the plates, electrons will not be able to travel through the capacitor and will begin to accumulate on the plate. Because of the repulsion of those electronics that are already on the plate, the battery will have insufficient energy to push any more electronics into the plate once a certain number of electronics have collected on the plate. The capacitor is fully charged at this stage. The first plate has generated a net negative charge, and the second plate has produced an equal net positive charge, resulting in an electric field with an attractive office between them that maintains the capacitor's charge.
Main Functions of Capacitor
A capacitor is an electrical component that stores and releases electricity in a circuit. It frequently sends alternating current instead of direct current. As a fundamental component of electrical equipment, a capacitor is usually always present in electronic circuits. The capacitor’s fundamental function is to store electrostatic energy in an electric field and, if feasible, to supply this energy to the circuit. To avoid a fatal circuit failure, they allow the AC to flow but restrict the DC from flowing. A capacitor can store electric energy when connected to its charging circuit. When unplugged from its charging circuit, it will discharge the collected energy, allowing it to be used like a temporary battery. The most typical application for capacitors is energy storage. Other uses include power condition, signal coupling or decoupling, electrical noise filtering, and remote sensing. Because of their numerous applications, capacitors are employed in a wide range of sec optics and have become an essential part of daily life.
FAQs on Capacitor Types
1. What is a capacitor and what is its primary function in an electronic circuit?
A capacitor is a fundamental passive electronic component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material called a dielectric. Its primary function is to store and release electrical energy, which allows it to perform various roles such as filtering out voltage fluctuations, blocking direct current (DC) while allowing alternating current (AC) to pass, and timing in circuits.
2. How are the different types of capacitors classified?
Capacitors are primarily classified based on the dielectric material used between their conductive plates. The choice of dielectric determines the capacitor's characteristics, such as capacitance value, voltage rating, and stability. Common types include:
- Electrolytic Capacitors: Use an electrolyte to form a very thin oxide layer as the dielectric (e.g., Aluminum, Tantalum).
- Ceramic Capacitors: Use a ceramic material as the dielectric. They are widely used for high-frequency applications.
- Film Capacitors: Use a thin plastic film as the dielectric (e.g., Polyester, Polypropylene).
- Paper Capacitors: Use paper as the dielectric, often impregnated with oil or wax.
3. What are the key differences between a fixed capacitor and a variable capacitor?
The key difference lies in their ability to change capacitance. A fixed capacitor has a constant, unchangeable capacitance value that is set during manufacturing. Examples include ceramic and electrolytic capacitors. In contrast, a variable capacitor is designed so that its capacitance can be intentionally and mechanically changed, typically by adjusting the overlapping area of its plates. These are often used in tuning circuits, like in analog radios, to select a specific frequency.
4. How is a basic parallel plate capacitor constructed?
A basic parallel plate capacitor is constructed using a simple arrangement of two flat, parallel conductive plates, often made of metals like aluminum. These plates are separated by a small distance, and the space between them is filled with a dielectric medium, which can be air, paper, mica, or ceramic. Electrical contacts or leads are attached to each plate to connect the capacitor into a circuit.
5. Which types of capacitors are suitable for AC circuits and why?
Non-polarised capacitors, such as ceramic capacitors and film capacitors, are suitable for AC circuits. This is because AC voltage continuously reverses its polarity. Polarised capacitors, like electrolytic types, have a specific positive and negative terminal and are designed to work with DC voltage. Applying an AC voltage or reversing the polarity on a polarised capacitor can damage or destroy its dielectric layer, leading to component failure.
6. How does inserting a dielectric material between the plates of a capacitor increase its capacitance?
When a dielectric is placed in the electric field between the capacitor's plates, its molecules become polarised. This polarisation creates an internal electric field within the dielectric that opposes the main electric field of the capacitor. This opposition effect reduces the overall potential difference (V) across the plates for the same amount of charge (Q). According to the formula for capacitance, C = Q/V, a decrease in voltage for the same charge results in an increase in the overall capacitance.
7. Why are electrolytic capacitors polarised while ceramic capacitors are not?
The polarisation of electrolytic capacitors is a result of their construction. They use an extremely thin oxide layer as the dielectric, which is formed through an electrochemical process on one of the plates. This layer provides insulation only when voltage is applied in the correct direction (polarity). Reversing the voltage can break down this fragile layer. In contrast, ceramic capacitors use a solid, stable ceramic material as the dielectric, which is inherently non-polar and functions identically regardless of the direction of the applied voltage.
8. How can a capacitor be compared to a rechargeable battery, and what are the key differences?
Both capacitors and batteries store and release electrical energy. However, they differ significantly:
- Storage Mechanism: A capacitor stores energy in an electric field, while a battery stores it through chemical reactions.
- Charge/Discharge Speed: Capacitors can charge and discharge almost instantly, which is ideal for applications needing quick bursts of energy. Batteries charge and discharge much more slowly.
- Energy Density: Batteries have a much higher energy density, meaning they can store significantly more energy for their size or weight compared to a capacitor.
- Lifespan: Capacitors can typically endure hundreds of thousands or millions of charge-discharge cycles with minimal degradation, whereas batteries have a limited cycle life.
9. What is the real-world role of a capacitor in a simple power supply filter circuit?
In a power supply, after AC is converted to pulsating DC by a rectifier, a capacitor acts as a smoothing filter. It is connected in parallel with the load. The capacitor charges up during the voltage peaks of the pulsating DC and then discharges its stored energy during the voltage troughs. This action fills in the gaps between pulses, significantly reducing the voltage variations (known as ripple) and providing a much smoother, more stable DC output required by most electronic devices.
10. Does a capacitor technically store charge or energy?
This is a common point of confusion. While a capacitor accumulates an equal amount of positive and negative charge on its opposite plates, it does not store net charge (the total charge is zero). More accurately, a capacitor stores potential energy in the electric field created between these separated charges. The work done to separate the charges is stored as energy, which is given by the formula U = ½ CV². Therefore, its primary function is to store energy.
