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Comprehensive Explanation of Capacitors

Author: Apogeeweb
Date: 21 Dec 2017
capacitor tutorial

Warm hints: The word in this article is about 5200 and the reading time is about 30 minutes.


Along with the electronic information technology changing rapidly, digital electronic product updates faster and faster, with the flat-panel TV (LCD and PDP) products, notebook computer, digital cameras, and other consumer electronic products production and sales continued to grow, driven by growth in the capacitor industry. In this article we will learn something about capacitors including what a capacitor is; the features of the capacitor, capacitor function; capacitor types; classification; capacitor formula; charging and discharging and etc.



Ⅰ Capacitor Introduction

Ⅱ Capacitor Features

Ⅲ Capacitor Function

Ⅳ Capacitor Model

Ⅴ Capacitor Clasification

Ⅵ Capacitor Types

Ⅶ Capacitor Capacitance

Ⅷ Charging and discharging

Ⅸ Attentions

Ⅹ Troubleshooting

Ⅺ New development

Ⅻ Super-capacitors




Ⅰ Capacitor Introduction

What are capacitors? The capacity to hold the charge is called usually the capacitance, we use the letter C to express it. Definition 1: The capacitor, as its name implies, is a 'container for electricity, a device that holds a charge. Capacitors are widely used in electronic devices, which are widely used in electronic devices. They are widely used in direct circuit switching, coupling, bypass, filtering, tuning loop, energy conversion, control and so on. Definition 2: A capacitor can be made up of two insulated and closely spaced conductors(Including wires).



About capacitance: The capacitance is different from the capacitor. The capacitance is the basic physical quantity, the symbol C, the unit is F (Fala).

Formula: The special formula of the general formula C=Q/U parallel plate capacitor: the electric field strength between the plates E=U/d, the capacitor's capacitive determinant C= S/4 PI KD


Along with the electronic information technology change rapidly, digital electronic product updates faster and faster, with the flat-panel TV (LCD and PDP) products, notebook computer, digital cameras and other consumer electronic products production and sales continued to grow, driven by growth in the capacitor industry.

various capacitors


Ⅱ Capacitor Features

Capacitors are composed of a layer of insulating dielectric between two metal electrodes. When a voltage is added between the two metal electrodes, the charge is stored on the electrode, therefore, the capacitor is an energy storage element. Any two conductors, which are insulated from each other and close to each other, make up a capacitor. The parallel plate capacitor consists of the pole plate and the dielectric of the capacitor. It has the following features:

  • 1. It has the capacity of charging and discharging characteristics and preventing the passing of DC current, allowing the passing of AC current.

  • 2. In the process of charging and discharging, the charge on the two plates has a process of accumulation, that is, the voltage has a process of establishment. Therefore, the voltage on the capacitor can not be mutated.

  • Capacitor Charging: two plates have equal different kinds of charge respectively, the absolute value of the charge of each plate is called the charge of the capacitor.


Capacitance charging process


  • Capacitor discharging: the positive and negative charge of the two poles of the capacitor is balanced out through the conductor. There is a short current on the wire during the discharge.

  • 3. The Capacitance of capacitor is inversely proportional to the frequency and capacity of the capacitor. So we say that analyzing capacitance size need to know the frequency and capacitance size of the signal.

  • 4. The capacitance formula of a parallel plate capacitor


The capacitance formula of parallel plate capacitor


Dielectric constant vacuum epsilon r=1, K as a static electric constant, S as two-plate positive pair area, D for two plate distance.

Attention: the electric field in the parallel plate capacitor is a uniform electric field


Ⅲ Capacitor Function

In a DC circuit, the capacitor is equivalent to a circuit breaker. The capacitor is a kind of element that can store the charge, as well as one of the most commonly used electronic components.


This has to be said from the structure of the capacitor. The simplest capacitor is made up of polar plates at both ends and dielectric (including air) in the middle. After electrifying, charged plate forming voltage (potential difference), but, due to the middle insulating material, so the capacitor is not conductive. However, this situation is under the condition that the critical voltage(breakdown voltage) of the capacitor is not exceeded. As we all know that any substance is relatively insulated. When the voltage at both ends of the material is increased to a certain extent, the matter can conduct electricity. We call this voltage breakdown voltage.


The capacitance is no exception, and when the capacitor is knocked out, it is not an insulator. But in the middle school stage, such voltage is not seen in the circuit, so it works below the breakdown voltage and can be seen as an insulator.




However, in the DC circuit, the direction of the current is changed with time to a certain degree of function. But the process of charging and discharging is time. At this time, the electric field which also a function of time is formed between the poles. Actually, the current pass by capacitors in the form of an electric field. The capacitor’s function is as follows:


1. Coupling: the capacitance used in the coupling circuit is called the coupling capacitance, which is widely used in the resistance-capacitance coupled amplifier and other capacitive coupling circuits, and it acts as a direct flow and alternating current.


2. Filtering: the capacitor used in the filter circuit is called the filter capacitor. In the power filter and various filter circuits, the capacitor circuit is used. The filter capacitor removes the signal from the total signal in a certain frequency band.


3. Decoupling: the capacitor used in the decoupling circuit is called a decoupling capacitor. The capacitor circuit is used in the DC voltage supply circuit of the multistage amplifier, and the decoupling capacitor eliminates the harmful low-frequency interconnection between the amplifiers.


4. High-frequency vibration elimination: capacitance used in high-frequency damping circuit is called high-frequency damping capacitor. In the audio negative feedback amplifier, in order to eliminate high-frequency self-excitation, we use this capacitance circuit to eliminate the possible high-frequency whistle of the amplifier.


5. Resonance: the capacitor used in the LC resonant circuit is called the resonant capacitance, and this capacitance circuit is required in both LC parallel and series resonant circuits.


6. Bypass: capacitor used in bypass circuit called the bypass capacitor in the circuit, if you need to remove the signal of a certain frequency from the signal, you can use a bypass capacitor circuit according to the signal frequency, a frequency domain (all AC signal) bypass capacitor circuit and a high-frequency bypass capacitor circuit.


7. Neutralization: the capacitor used in the neutralization circuit is called neutralization capacitance. In radiofrequency and medium frequency amplifiers, high-frequency amplifiers in TV sets, this neutralization capacitor circuit is used to eliminate self-excitation.


8. Timing: the capacitor used in the timing circuit is called the timing capacitance. The use of a timing capacitance circuit in a circuit that needs to charge and discharge the time by capacitor charging and discharging, and the function of the capacitor to control the time constant size.


9. Integral: the capacitor used in an integrated circuit is called an integral capacitor. In the synchronous separation circuit of the potential field scanning, the field synchronous signal can be taken out of the field compound synchronous signal by using this integral capacitor circuit.


10. Differential: a capacitor used in a differential circuit is called a differential capacitance. In order to get spike trigger signal in trigger circuit, we use this differential capacitance circuit to get spike pulse triggering signal from all kinds of (mainly rectangular pulse) signals.


11. Compensation: compensation capacitors used in the circuit are called the compensation capacitor, the compensation circuit card in the bass, the low-frequency compensation capacitor circuit, in order to improve the low-frequency signal, a playback signal in addition to this, there is a high-frequency compensation capacitor circuit.


12. Bootstrap: the capacitor used in bootstrapping circuit is called the bootstrap capacitor. The output circuit of the OTL power amplifier usually uses this bootstrap capacitor circuit to enhance the positive half-width of the signal by positive feedback.


13. Frequency division: the capacitor in the frequency divider is called the frequency divider capacitor. In the loudspeaker frequency divider, the frequency divider circuit is used to make the high-frequency loudspeaker work in the high-frequency section, the intermediate frequency loudspeaker operates in the middle frequency band, and the low-frequency loudspeaker works in the low-frequency section.


14. Load capacitance: it refers to the effective external capacitance of the quartz crystal resonator to determine the resonant frequency of the load. The standard values of load capacitors are 16pF, 20pF, 30pF, 50pF and 100pF. The load capacitance can be adjusted properly according to the specific conditions. By adjustment, the working frequency of the resonator can be adjusted to the nominal value.


Ⅳ Capacitor Model

Model Naming

The type of capacitor made in China is generally composed of four parts (not suitable for pressure-sensitive, variable, vacuum capacitors). In turn, they represent names, materials, classifications and ordinal numbers.

The first part: the name, the alphabet, the capacitor used in C.

The second part: material, expressed in letters.

The third part: classification, generally represented by numbers, and individual letters.

The fourth part: the serial number, which is represented by the number.

With the letter said the product material air conditioner fittings: A- tantalum electrolytic capacitor B-, polystyrene and other non-polar films, C-, D-, high-frequency ceramic aluminum electrolysis, E- other materials of G- alloy and H- composite medium, I- glass glaze, J- metalized paper and L- polyester and other polar organic thin film, electrolytic niobium N- O- film, Q- film, glass, ceramics, V- T- low-frequency Y- Z-, mica paper, mica paper


 Capacity Marking

  • 1. direct method

  • Use the number and unit symbol to mark directly. 1uF represents 1 Micro method, some capacitors use "R" to represent decimal points, such as R56 for 0.56 Micro methods.

  • 2. word symbol method

  • Capacity is represented by a regular combination of numeric and literal symbols. For example, P10 indicates that 0.1pF, 1p0 means 1pF, 6P8 means 6.8pF, 2u2 is 2.2uF.

  • 3. color standard method

  • The main parameters of the capacitor are expressed with a color ring or a color point. The color mark method of the capacitor is the same as the resistance.

  • Capacitor bias sign symbols: +100%-0--H, +100%-10%--R, +50%-10%--T, +30%-10%--Q, +50%-20%--S, +80%-20%--Z

  • 4.mathematical counting method

  • the mathematical counting method is generally three-digit numbers, the first and second digit numbers are valid numbers, and the third digit numbers are multiple. If the value is 272,the capacity: 27X10^2=2700pf. In other words, if the value is 47X10^3=47000pf (473, 2, 3 behind, said many times 10). The same as 332=33X10^2=3300pf. Look at the following cable:

First part(name, Use letter C to express)

Second part(material Use letters to express)

Third part(Classified, use numbers to express, as well as alphabetical terms)

Fourth part(symbol, use number to express to distinguish the size and performance)


letters meanings




Ceramic capacitor

Mica capacitance

Organic capacitance

Electrolytic capacitor


A - Tantalum electrolysis






B - polystyrene and other nonpolar films










Sintered powder solid


C-high frequency ceramics






D-aluminum electrolysis


Pierce the heart


Pierce the heart



E - other materials electrolysis


Prop, etc.




G - alloy electrolysis






H - composite medium





Non polarity

I - glass glaze


high pressure

high pressure

High pressure


J metalized paper






L - polyester and other polar organic films


High power





N - niobium electrolysis




O - glass film


Q - lacquer film


metalized paper


T-low frequency ceramics


V - mica paper


High pressure








Ⅴ Capacitor Clasification

According to the analysis and statistics, the capacitor can be divided into the following 10 categories:

  • 1. according to the structure, it is divided into three major categories: fixed capacitor, variable capacitor and micro capacitor.

  • 2. classified by electrolytes: organic dielectric capacitors, inorganic dielectric capacitors, electrolytic capacitors, electric capacitors and air dielectric capacitors.

  • 3. It is divided into high-frequency bypass, low-frequency bypass, filtering, tuning, high-frequency coupling, low-frequency coupling, small capacitor.

  • 4. according to the production of different materials can be divided into ceramic capacitors, polyester capacitors, electrolytic capacitors, tantalum capacitors, and advanced polypropylene capacitor, etc.

  • 5. high-frequency bypass: ceramic capacitor, mica capacitor, glass film capacitor, polyester capacitor, glass glaze capacitor.

  • 6. low-frequency bypass: paper capacitor, ceramic capacitor, electrolytic capacitors, polyester capacitors.

  • 7, filter: aluminum electrolytic capacitor, capacitor, composite paper capacitor, wet tantalum capacitors.

  • 8. tuning: ceramic capacitor, mica capacitor, glass film capacitor, polystyrene capacitor.

  • 9. low coupling: paper capacitor, ceramic capacitor, electrolytic capacitors, polyester capacitors, solid tantalum capacitors.

  • 10. small capacitors: Metallized paper capacitor, ceramic capacitor, electrolytic capacitors, polystyrene capacitors, solid tantalum capacitors, glass glaze capacitors, metalized polyester capacitors, polypropylene capacitors, mica capacitor.


Capacitor Types

Aluminum electrolytic capacitor

Soaked with water or paste electrolyte in two aluminum foil intermediate winded thin oxide film for capacitor medium. Because of the unidirectional conductivity of the oxide film, the electrolytic capacitor has polarity. It has a large capacity and can withstand a large pulsating current.

Large capacity error, large leakage current, common unfit for high frequency and low-temperature application, it is not appropriate to use the frequency above 25kHz. Low-frequency bypass, signal coupling, power filter.


Tantalum electrolytic capacitor

The sintered tantalum block is used as the positive pole, and the electrolyte is made of solid manganese dioxide.

The temperature characteristics, frequency characteristics and reliability are better than those of common electrolytic capacitors, especially the leakage current is very small. The storage capacity is good, the life is long, the capacity error is small, and the volume is small, and the maximum capacitance-voltage product can be obtained under the unit volume.

The resistance to the pulsating current is poor, and if the damage is easy it is short-circuited. In super small and high-reliability parts.


Self-healing shunt capacitor

The structure is similar to the paper capacitor, but it is medium with a low-loss plastic material such as polystyrene and polystyrene. The frequency characteristic is good and the dielectric loss is small. It can not make large capacity, poor heat resistance.

Filters, integrals, oscillations, timing circuits. Ceramic capacitor bushing type or pillar structure ceramic capacitor, an electrode which is a mounting screw. The inductor of the lead is very small. The frequency characteristic is good, the dielectric loss is small, and it has the effect of temperature compensation.

It can not make large capacity, vibration will cause capacity change. It is especially suitable for high-frequency bypass.


Single stone capacitor (multilayer ceramic capacitor)

A number of ceramic thin film billets are coated with electrode paddle materials, which are folded and formed into an inseparable whole, and the outside is encapsulated with resin.

New capacitors with small volume, large capacity, high reliability and high-temperature resistance as well as low dielectric constant monolithic capacitors with high dielectric constant also have a stable performance with small volume and high Q value. The capacity error is big. Bypass, noise filter, an oscillator circuit, integral capacitor

Generally, two aluminum foil is used as the electrode, and the capacitor paper with a thickness of 0.008~0.012mm is separated and coiled in the middle. The manufacturing process is simple, the price is cheap, and the capacity is larger.


Metalized polypropylene capacitor

Generally, in low-frequency circuits, it is usually not used at a frequency above 3 to 4MHz. The oil-immersed capacitor has higher withstand voltage than an ordinary paper capacitor and good stability. It is suitable for high-voltage circuit trimming capacitor (semi-variable capacitor) capacitance can be adjusted in a small range, and it can be fixed to a capacitance value after adjustment.

The ceramic capacitor has a high Q value, and a small size usually can be divided into the cylindrical tube and disc type two. The mica and polystyrene medium usually adopt spring East, with simple structure but poor stability. Wire wound ceramic capacitor is removed to change the "outer" wire electrode capacitance, so the capacity can only become small, not suitable for repeated debugging on the occasion to use.


Ceramic capacitor

A high permittivity capacitor ceramic, BaTiO3 titanium oxide, was extruded into circular tubes, wafers, or discs as a medium, and silver was plated on ceramics as an electrode by means of burning infiltration. It is divided into high frequency and low frequency of two kinds of ceramic.

A capacitor with a small positive capacitance temperature coefficient, used in high stability oscillating circuits as loop capacitors and cushions. A low-frequency ceramic capacitor is limited to a relatively low-frequency circuit for bypass or DC blocking, or loss of stability and less demanding situations, including the "high frequency". This capacitor should not be used in pulse circuits because they are easily breakdown by pulse voltage.


High-frequency ceramic capacitor

A high-frequency ceramic capacitor is suitable for a high-frequency circuit mica capacitor.

As far as the structure is concerned, it can be divided into chaff and silver, the silver electrode is directly deposited on the mica sheet by vacuum evaporation or burning infiltration method. Because the air gap is eliminated, the temperature coefficient decreases greatly, and the capacitance stability is higher than that of the foil type.

The frequency characteristic is good, the Q value is high, the temperature coefficient is small. It’s not suitable to make large capacity. It is widely used in high-frequency electrical apparatus and can be used as a standard capacitor glass glaze capacitor A special mixture suitable for spraying is sprayed into a film, and the medium is then sintered with a silver layer electrode to form a "single stone" structure.

The performance is comparable to the mica capacitor, and it can withstand all kinds of climatic conditions. It can work at 200 500V or higher. The rated working voltage is up to 500V, and the loss is TG to 0.0005 ~ 0.008.


Air pump capacitor

Capacitors: electronic devices serve as rectifiers like smoothing filters, power supply and decoupling, bypass of AC signal, AC and DC circuit coupling are called capacitors.

The capacitor comprises a fixed capacitor and a variable capacitor two categories, including fixed capacitors can be used according to the material is divided into mica capacitors, ceramic capacitors, paper / plastic film capacitors, electrolytic capacitors and glass glaze capacitors; variable capacitors can also be glass, ceramic or air medium structure.

There is a great relationship between the loss of the capacitor and the temperature of the electric leakage and the use of the environment!


The detection method of fixed capacitor

  • A. detects the small capacitance below 10pF because the capacity of the fixed capacitor below 10pF is too small to measure with a multimeter. It can only qualitatively check whether it has leakage, internal short circuit, or breakdown. When measurements can be used multimeter R * 10K block, two-pin two probes are respectively arbitrary capacitance, resistance should be infinite. If the resistance is measured (the pointer swings to the right) to zero, the leakage damage or internal breakdown of the capacitor is explained.

  • B. detection of 10PF ~ 001 mu F fixed capacitor charging phenomenon, and then judge it's good or bad. R x 1K gear is selected for the multimeter. The beta values of the two triodes are more than 100, and the penetration current is small. 3DG6 and other types of silicon triode can be used to make a composite pipe. Multimeter red and black pen respectively with the composite pipe emitter and collector e c. Because of the magnification of the compound triode, the charging and discharging process of the measured capacitance is magnified, so that the swing of the pointer of the multimeter is increased, so it is easy to observe. 


It should be noted that when testing operation, especially when measuring capacitance with smaller capacitance, it is necessary to repeatedly change the measured capacitance pin contacts A and B two points to see the swinging of the multimeter pointer clearly. C, for a fixed capacitance of more than 001 F, it can directly test whether the capacitor is charging or not and whether it has an internal short circuit or electric leakage by using the R R 10K of the multimeter. It can also estimate the capacitance of the capacitor according to the magnitude of the swing of the pointer to the right.


See the introduction and dis-assembly of capacitors intuitively, click the following video: 


Ⅶ Capacitor Capacitance

Since the capacitor is a "container" for storing charge, there is a problem of "capacity". In order to measure the capacity of the capacitor to store the charge, the physical quantity of the capacitance is determined. The capacitor must be able to store the charge under the effect of an applied voltage. The amount of charge stored by different capacitors under the action of voltage may also be different. Internationally, the amount of electric charge that a capacitor can add to 1 volt DC voltage is regulated by the letter C. The basic unit of capacitance is Fala (F).


Under the action of 1 volt DC voltage, if the charge of the capacitor is 1 Coulomb, the capacitance is fixed to 1 Fala, and Fala is represented by the symbol F, 1F=1Q/V. In practical application, the capacitance of the capacitor is much smaller than the 1 Fala, commonly used in small units, such as millifarad (mF), micro method (F), neffa (nF), skin (pF), the relationship between them is: 1 micro method is equal to one-millionth of Fala; 1 the skin was equal to one-millionth of a micro method, namely :

  • 1 Fala (F) =1000 (mF) millifarad

  • 1 millifarad (mF) =1000 micro method (F)

  • 1 micromethod (mu F) =1000 nano method (nF)

  • 1 Nana method (nF) =1000 skin method (pF)

  • That is:

  • 1F=1000000 mu F

  • 1μF=1000000pF


Ⅷ Charging and discharging

When the capacitor is switched on, under the action of electric field force, free electrons and positive power supply are connected through the power capacitor plate will move to the plate is connected with a power supply anode, cathode and positively charged due to the loss of negative charge, negative due to a negative charge and a negative charge, positive and negative plates with an equal charge, on the contrary, the symbol. The directional movement formed charge current, due to rejection of the same charge, so start current maximum, then gradually decreased, the charge transfer process, charge storage capacitor plate increasing, capacitor two inter plate voltage of Uc is equal to the supply voltage U charge to stop moving, the switch is closed, the current of I=0.


Connecting wire, capacitor charge neutralization of positive and negative plates. When the K is closed, the capacitor C cathode positive charge can move in and out of the negative, negative charge can be moved to it In extreme neutralization, the charge decreases gradually, the performance current decreases, and the voltage decreases to zero.


Ⅸ Attentions

Because the two poles of the capacitor have the characteristics of the remaining residual charge, the electric charge should be put out first, otherwise, the electric shock accident will occur easily. Handle the faulted capacitor, first opened circuit breaker capacitors and upper and lower isolating switch, such as the use of fuse protection, you should remove the fuse tube. At this point, although the capacitor bank has been discharged by the discharge resistance, there will still be some residual charge.


Therefore, the artificial discharge must be carried out. When discharging, it is necessary to fix the grounding terminal and grounding grid of the grounding wire first, then discharge the capacitor repeatedly to the capacitor until the spark and the discharge sound is released. Finally, the grounding wire is fixed. At the same time, we should also notice that if the capacitor has internal disconnection, fuse or lead contact is not good, there may be residual charge between the poles, while the residual charge will not be released when automatic discharge or artificial discharge occurs.


So the operation or maintenance personnel should wear insulated gloves before contact with the faulty capacitor and connect the two poles of the faulted capacitor in a short route to discharge them. In addition, the capacitor that uses series connection mode should be discharged separately.




Ⅹ Troubleshooting

1.Some common faults of capacitors are listed as following. 

The power should be cut off immediately when one of the following situations of the capacitor has been founded.

  • (1) the capacitor housing expands or leaks oil.

  • (2) casing rupture, flashover and sparking.

  • (3) the internal sound of the capacitor is abnormal.

  • (4) the temperature rise of the shell is higher than that above 55 degrees centigrade.


2. Fault handling of the capacitor

  • (1)When the capacitor exploded, the power was disconnected immediately, and the sand and dry extinguished the fire.

  • (2)When the capacitor’s insurance is fusing, it should report to the dispatch and then open the circuit breaker of the capacitor after the agreement is obtained. Cut off the power discharge of the first external examination, such as the external casing has no signs of flashover, whether the deformation of the shell, leakage and grounding device has not short circuit phenomenon and measuring pole and pole of the insulation resistance value, check the connection of capacitor bank is complete. If there is a lack of solid-phase the phenomenon, such as found no fault phenomenon, can be good for insurance investment. If the insurance is still fusing after the power supply, the faulted capacitor shall be exited and the rest of the power supply will be restored. If the safety of the fuse, the circuit breaker also jumps, at this time can not be forced to send. It is necessary to wait for the above inspection to be completed and then put into the insurance.

  • (3) the circuit breaker tripping of capacitors and the branch insurance is not broken. The capacitor should be discharged for three minutes before checking the circuit breaker current transformer, power cable and capacitor outside. If the exception is not found, it may be due to the voltage fluctuation of the external fault bus. After inspection, can throw; otherwise, should be further protection of the comprehensive power test. Through the above inspection and test, if the cause can not be found, the system should be handled according to the system, and the capacitor will be tested gradually. Before trying to find out the reason and not.


3.Safety matters when dealing with fault capacitors

After disconnecting the circuit breaker of the capacitor, the faulted capacitor should open the isolation switch on both sides of the circuit breaker and carry out the capacitor bank after discharge. The capacitor discharge resistance, discharge or discharge of transformer voltage transformer after discharge, because some residual charge temporarily put not, should be a ground end fixed, and then the grounding rod repeatedly to discharge the capacitor until no spark and acoustic, and then fixed the grounding clip. Because the faulted capacitor could have a bad contact wire, internal fuse disconnection, or other phenomena, it may still have some charge is not put out, so the maintenance personnel in contact with the faulted capacitor before, should wear insulated gloves, with a short line will be two electrodes of the capacitor short circuit fault, should also be discharge alone.


Ⅺ New development

French researchers reported that the more irregular the structure of carbon materials used to make supercapacitor electrodes, the greater the capacitance of the supercapacitors, the stronger the ability to withstand high pressure. The supercapacitor is a new type of energy storage device, which has the advantages of short charging time, high output power and long life. It can be applied to vehicle braking energy recovery systems. The working principle is based on the interaction between positive and negative ions in the electrode and electrolyte. The larger the electrode surface area and the stronger the interaction with positive and negative ions, the greater the capacitance.


The French national scientific research center and the Orlean University researchers with the technology of quantitative nuclear magnetic resonance spectroscopy analysis of the electrostatic interactions between the electrodes, and the positive and negative ions were found, the more irregular structure of carbon electrode materials, supercapacitor capacitance is greater, the pressure bearing capacity is strong. The paper is published on the web version of the journal Nature Materials. The researchers believe that this discovery helps people to improve the performance of supercapacitors.


Ⅻ Super-capacitors

Supercapacitors are maximum capacity capacitors with a capacitance of up to thousands of Fala. According to the principle of the capacitor, the capacitance depends on the distance between the electrode and the electrode surface area, in order to get such a large amount of capacitance, to minimize the distance between the supercapacitor electrode and increasing the electrode surface area, therefore, the principle of electric double layer and active carbon porous electrode.


super capacitor

When the voltage is applied to the two electrodes of the supercapacitor double layer dielectric, the charge opposite to the electrode is generated on the dielectric interface near the electrode and is bound to the dielectric interface to form the two electrodes of the capacitor. Obviously, the distance between the two electrodes is very small, only a few nm. At the same time, the activated carbon porous electrode can obtain a great surface area of the electrode, which can reach 200m2/g. Therefore, the super-capacitor of this structure has great capacitance and can store a lot of electrostatic energy. As far as energy storage is concerned, this characteristic of the super-capacitor is between the traditional capacitor and the battery.


When the two electrode plate potential is lower than the electrolyte oxidation-reduction potential, electrolyte interface charge does not deviate from the electrolyte, supercapacitor in normal working condition (usually below 3V), if the capacitor voltage exceeds two oxidation-reduction potentials of the electrolyte, the electrolyte decomposition, so, in a non-normal state.


With the discharge of the super-capacitor, the charge on the positive and negative plate is discharged by the external circuit, and the charge response on the electrolyte interface is reduced. It can be seen that the charge-discharge process of super-capacitors is always a physical process, without chemical reaction, so the performance is stable, which is different from that of batteries that use chemical reaction.



1. What's the function of capacitors?

Its function is to store the electrical energy and give this energy again to the circuit when necessary. In other words, it charges and discharges the electric charge stored in it. Besides this, the functions of a capacitor are as follows: It blocks the flow of DC and permits the flow of AC.


2. What's a capacitor and its principle?

A capacitor is a device that is used to store charges in an electrical circuit. A capacitor works on the principle that the capacitance of a conductor increases appreciably when an earthed conductor is brought near it. Hence, a capacitor has two plates separated by a distance having equal and opposite charges.


3. What are the different types of capacitors?

The different types of capacitors are following.

• Electrolytic Capacitor.

• Mica Capacitor.

• Paper Capacitor.

• Film Capacitor.

• Non-Polarized Capacitor.

• Ceramic Capacitor.


4. What is the importance of a capacitor?

Capacitors have many important applications. They are used, for example, in digital circuits so that information stored in large computer memories is not lost during a momentary electric power failure; the electric energy stored in such capacitors maintains the information during the temporary loss of power.


5. What is the formula for capacitors in parallel?

This is shown below. To calculate the total overall capacitance of a number of capacitors connected in this way you add up the individual capacitances using the following formula: CTotal = C1 + C2 + C3 and so on Example: To calculate the total capacitance for these three capacitors in parallel.


6. Which side of the capacitor symbol is positive?

The positive or anode side of the capacitor is marked with a '+' symbol. Since electrolytic capacitors are polarized, I use a symbol (shown below) on my schematics.


7. What happens if I use the wrong capacitor?

If the wrong run capacitor is installed, the motor will not have an even magnetic field. This will cause the rotor to hesitate at those spots that are uneven. This hesitation will cause the motor to become noisy, increase energy consumption, cause performance to drop, and cause the motor to overheat.


8. What does K mean on a capacitor?

K is for thousand. When a Capacitor is used, the implied unit is the Picofarad. 470,000 picofarads or 0.47 microfarads is what 470k on a capacitor means.


9. What does uF mean on the capacitor?

uF refers to the size of the capacitor. Capacitance is the charge that is necessary to raise the potential of a body one unit. A capacitance of 1 farad (f) requires 1 coulomb of electricity to raise its potential 1 volt (v). 1 micro farad (uF) = 0.0000001 F. Dannie Musser.


10. Are capacitors color-coded?

The capacitors use a capacitor color code similar to the resistors' color code (3, 4 or 5 bands). The first two colors indicate significant digits of the value of the capacity (in pF), the next color is the corresponding power of 10, the other two colors are optional and indicate tolerance and maximum voltage.



Book Recommendation

  • Capacitors: Technology and Trends

"Capacitor technology is changing rapidly in sync with emerging applications. Capacitors are increasingly being used for energy storage in UPS systems, in cellular phones, cameras and automobiles. In power utility grids, capacitors continue to enhance transmission capacity and reduce losses. Capacitors: Technology and Trends provides the reader not only current usage and trends for its application in the electrical and electronic sectors but also the basics of capacitor physics and the evolution of raw materials and manufacturing processes. The book aims to serve as a ready reference to students, researchers, manufacturers and users of capacitors. Advance praise Capacitors: Technology and Trends is hence ideal, in its content and timing. This book, I’m certain will serve as a ready reference to students, researchers, as also all manufacturers and users of capacitors in electrical and electronic industry.” Vinod Sharma, Managing Director DEKI Electronics Ltd, New Delhi “I believe this book is a treasure trove in one’s library in today’s industrial world especially for the project and design managers.” Himanshu Dalvi, President (L) Orient Paper & Industries Ltd “I think this could be a good reference book for universities and colleges to use, since they often do not teach very much about capacitors.” 

--R P Deshpande (Author)

  • The Capacitor Handbook: A Comprehensive Guide For Correct Component Selection In All Circuit Applications. Know What To Use When And Where.

This book provides practical guidance and application information when using capacitors in electronics and electrical circuit design. This easy-to-use book covers the following capacitor types: Ceramic, Plastic Film, Aluminum Electrolytic, Tantalum, Glass, Mica, and others. This book also has a very comprehensive Glossary and Index. The Selection Guidelines and the Symbols and Equations sections have the answers to all of your daily application questions. This book is one in a series of component handbooks.

--Cletus J. Kaiser (Author)



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