Online Unit Converters • Electrical Engineering • Capacitance • Compact Calculator Overview Measuring the capacity of the capacitor with nominal capacitance of 10 μF, using a multimeter oscilloscope. Capacitance is a physical quantity that represents the ability of a conductor to accumulate charge. It is found by dividing the electrical charge magnitude by the potential difference between conductors: C = Q/∆φ Here Q is electric charge, which is measured in coulombs (C), and ∆φ is the potential difference, which is measured in volts (V). Capacitance is measured in farads (F) in SI. This unit is named after the British physicist Michael Faraday. One farad represents extremely large capacitance for an isolated conductor. For example, an isolated metal ball with the radius 13 times greater than that of the Sun would have capacitance of one farad, while the capacitance of a metal ball with the radius of the Earth would be about 710 microfarads (μF).

Because one farad is such a large quantity, smaller units are used, such as microfarad (μF), which equals one millionth of a farad, nanofarad (nF), equalling to one billionth of a farad, and picofarad (pF), which is one trillionth of a farad. In the extended CGS for electromagnetic units the main unit of capacitance is described using centimeters (cm). One centimeter of electromagnetic capacitance represents capacitance of a ball in vacuum that has the radius of 1 cm. CGS system stands for centimeter-gram-second system — it uses centimeters, grams, and seconds as the basic units for length, mass, and time. Extensions of CGS also set one or more constants to 1, which allows to simplify certain formulas and calculations. Uses for Capacitance Capacitors — Electronic Components for Storing Electric Charges Electronic symbols Capacitance is a quantity, relevant not only for electrical conductors but also for capacitors (originally called condensers). Capacitors consist of two conductors divided by a dielectric or vacuum. The simplest version of a capacitor has two plates that act as electrodes.

A capacitor (from the Latin condensare — to condense) is a double-layer electronic component used for storing electric charge and energy of the electromagnetic field. The simplest capacitor consists of two electrical conductors, with a dielectric between them. Radio electronics enthusiasts are known to make trimmer capacitors for their circuits with the different diameter enameled wires. The thinner wire is wrapped around the thicker one. The RLC circuit is set to the desired frequency by changing the number of turns of the wire. The image has some examples of how a capacitor can be represented in a circuit diagram. Parallel RLC circuit: a resistor, an inductor and a capacitor Some History Scientists were able to make capacitors as far as 250 years ago. In 1745 in Leyden the German physicist Ewald Georg von Kleist and a physicist from the Netherlands Pieter van Musschenbroek made the first capacitor device that was called a “Leyden jar”. The walls of the jar served as dielectric, while the water in the jar and the hand of the experimenter acted as conductor plates. Such a jar could accumulate a charge of about one microcoulomb (µC).

Experiments and demonstrations with the Leyden jars were popular at the time. In them the jar was charged with static electricity by using friction. A participant of the experiment would then touch the jar and experience an electric shock. Once 700 monks in Paris conducted the Leyden experiment. They held hands and one of them touched the jar. At that moment all 700 people exclaimed in horror as they felt the jolt. The “Leyden jar” came to Russia thanks to the Russian Tsar Peter the Great. He met with Pieter van Musschenbroek during his travels in Europe and became acquainted with his work. When Peter the Great established the Russian Academy of Sciences, he commissioned Musschenbroek to make various equipment for the Academy. As time went by, capacitors have been improved, with their size decreasing as the capacitance increased. Today capacitors are widely used in electronics. For example, a capacitor and an inductance coil create a resistor, inductor, and capacitor circuit, also known as an RLC or an LCR or a CRL circuit. This circuit is used to set receiving frequency on a radio.

There are several types of capacitors that differ in whether their capacitance is constant or variable, and in the type of dielectric material used. Examples of Capacitors Electrolytic capacitors in the power supply unit. There are many different kinds of capacitors made today for a range of uses, but their main classification is based on their capacitance and rated voltage. Generally capacitance of capacitors falls between several picofarads to several hundred microfarads. Supercapacitors are an exception to this, because their capacitance is formed differently, compared to other capacitors — it is, in fact, double-layer capacitance. This is similar to the operating principle of electrochemical cells. Supercapacitors, which are built with carbon nanotubes, have an increased capacitance because of a larger surface of the electrodes. Capacitance of supercapacitors is tens of farads, and sometimes they can replace electrochemical cells as a source of electric current. The second most important property of a capacitor is its rated voltage. Exceeding this value may render the capacitor unusable.

This is why when building circuits it is common to use capacitors with the value for rated voltage that is double compared to the voltage applied to them in the circuit. This way even if the voltage in the circuit slightly increases above the norm, the capacitor should be fine, as long as the increase does not become double the norm. Capacitors can be joined together to create batteries in order to increase the total rated voltage or capacitance of the system. Connecting two capacitors of the same type in series doubles the rated voltage and decreases the total capacitance in half. Connecting the capacitors in parallel results in doubling the total capacitance, while rated voltage stays the same. The third most important property of capacitors is their temperature coefficient of capacitance. It reflects the relationship between capacitance and temperature. Depending on their intended use capacitors are classified into general purpose capacitors, which do not have to meet high-level requirements, and special capacitors. The latter group includes high voltage capacitors, precision capacitors, and those with different temperature coefficients of capacitance. Capacitor Markings Similar to resistors, capacitors are marked according to their capacitance and other properties.

The marking could include information on nominal capacitance, the degree of deviation from the nominal value, and rated voltage. Small scale capacitors are marked with three or four digits or an alpha-numeric code, and they can also be color-coded. Tables with codes and their corresponding rated voltage, nominal capacitance, and temperature coefficient of capacitance are available online, but the most reliable way to verify the capacitance and to find out if the capacitor is operating properly is to remove the capacitor from the circuit and to take measurements by using a multimeter. Disassembled electrolytic capacitor. It is constructed from two aluminum foils. One of them is coated by an insulating oxide layer and is acting as the anode. A paper soaked in electrolyte together with another foil is acting as the cathode. The aluminum foil is etched to increase its surface area. A word of caution: capacitors can store a very large charge at a very high voltage. To avoid an electric shock it is paramount to take precautions before taking measurements. In particular, it is important to discharge capacitors by short-circuiting their leads with a wire that is insulated with a highly resistant material. Regular wires of a measuring device would work well in this situation.

Electrolytic capacitors: these capacitors have large volumetric efficiency. This means that they have a large capacitance for a given unit of the capacitor’s weight. One of the plates of such a capacitor is usually an aluminum ribbon, covered with a thin layer of aluminum oxide. The electrolytic fluid acts as the second plate. This fluid has electrical polarity, therefore it is paramount to ensure that such a capacitor is added to the circuit correctly, according to its polarity. Polymer capacitors: these types of capacitors use a semi-conductor or an organic polymer that conducts electricity instead of electrolytic fluid as the second plate. Their anode is usually made of metal such as aluminum or tantalum. Variable capacitors: the capacitance of these capacitors can be changed mechanically, by adjusting electrical voltage, or by varying temperature. Film capacitors: their capacitance can range from 5 pF to 100 μF. There are also other types of capacitors. Supercapacitors Supercapacitors are becoming popular these days. A supercapacitor is a hybrid of a capacitor and a chemical power supply source. The charge is stored at the border where the two media, the electrode and the electrolyte meet.

The first electrical component that was the predecessor of a supercapacitor was patented in 1957. It was a capacitor with a double electric layer and porous material used, which helped increase the capacity because of the increased surface area. This approach is known now as double layer capacitance. The electrodes were coal-based and porous. Since then the design has been constantly improved, and the first supercapacitors appeared on the market in the early 1980s. Supercapacitors are used in electric circuits as a source of electric energy. They have a number of advantages over traditional batteries, including their longevity, small weight, and fast charging. It is likely that due to these advantages supercapacitors will replace batteries in the future. The main drawback of using supercapacitors is that they produce a smaller amount of specific energy (energy per unit of weight), and that they have low rated voltage, and large self-discharge. In Formula 1 races supercapacitors are used in energy recuperation systems. The energy is generated when the vehicle slows down. It is stored in the flywheel, the battery, or the supercapacitors for further use. Electric car A2B made at the University of Toronto.

General view In consumer electronics supercapacitors are used to ensure stable electric current or as a backup power supply. They often provide power during the peaks for power demand in devices that use battery power and have variable electrical demand, such as MP3 players, flashlights, automated utility meters, and other devices. Supercapacitors are also used in public transit vehicles, especially in trolleybuses, because they allow for higher maneuvering ability and self-contained motion when there are problems with the external power supply. Supercapacitors are also used in some buses and electric cars. Electric car A2B made at the University of Toronto. Under the hood These days many companies produce electric cars, including General Motors, Nissan, Tesla Motors, and Toronto Electric. A research group at the University of Toronto together with the electric motor distributor company Toronto Electric developed a Canadian model of an electric car, A2B. It uses both chemical sources of energy and supercapacitors — this way of storing energy is called hybrid electric storage. The engines of this electric car are powered by the batteries that weigh 380 kg. Solar panels are also used for additional charge — they are installed on the car’s roof.

Capacitive Touchscreens In modern devices the use of touchscreens that control devices through touching panels or screens is on the increase. There are different types of touchscreens, including capacitive and resistive screens, as well as many others. Some can only react to one touch, while others react to multiple touches. Working principles of the capacitive screens are based on the fact that a large body conducts electricity. This large body in our case is the human body. Surface Capacitance Touchscreens Sensor screen for the iPhone is made using the projected capacitance technology. A surface capacitance screen is made of a glass panel, coated with a transparent resistive material. Generally this material is highly transparent and has low surface resistance. Often the alloy of indium oxide and tin oxide is used. The electrodes in the corners of the screen apply low fluctuating voltage on the resistive material. When a finger touches this screen, it creates a small leakage of the electrical charge. This leakage is detected in the four corners by the sensors and the information is sent to the controller, which determines the coordinates of the touch. The advantage of these screens is in their longevity. They can withstand touch as frequently as once per second for up to 6.5 years.

This translates to about 200 million touches. These screens have a high, up to 90%, transparency rate. Because of their advantages, capacitive touchscreens have been replacing resistive touchscreens on the market since 2009. The disadvantages of capacitive screens are that they do not work well in sub-zero temperatures, and that it is difficult to use them while wearing gloves, because gloves act as an insulator. The touchscreen is sensitive to exposure to the elements, therefore if it is located on the external panel of the device, it is only used in the devices that protect the screen from exposure. Projected Capacitance Touchscreens Besides surface capacitance screens, there are also projected capacitance touchscreens. They differ in that there is a net of electrodes on the inside of the screen. When the user touches the electrode, the body and the electrode work together as a capacitor. Thanks to the net of electrodes it is easy to get the coordinates for the area of the screen that was touched. This type of screen reacts to touch even if the user is wearing thin gloves. Projected capacitance touchscreens also have high transparency, up to 90%.

They are durable and long-lasting, and this makes them popular not only in personal electronic devices, but also in devices meant for public use, including those outside, such as vending machines, electronic payment systems, and others. This article was written by Sergey Akishkin , Tatiana Kondratieva You can hide articles if you use this converter often. Cookies must be allowed in your browser. You may be interested in another converters in the Electrical Engineering group: Learn Technical English with Our Videos! You can use this online converter to convert between several hundred units (including metric, British and American) in 76 categories, or several thousand pairs including acceleration, area, electrical, energy, force, length, light, mass, mass flow, density, specific volume, power, pressure, stress, temperature, time, torque, velocity, viscosity, volume and capacity, volume flow, and more. Note: Integers (numbers without a decimal period or exponent notation) are considered accurate up to 15 digits and the maximum number of digits after the decimal point is 10. In this calculator, E notation is used to represent numbers that are too small or too large. E notation is an alternative format of the scientific notation a · 10x.

For example: 1,103,000 = 1.103 · 106 = 1.103E+6. Here E (from exponent) represents “· 10^”, that is “times ten raised to the power of”. E-notation is commonly used in calculators and by scientists, mathematicians and engineers. Select the unit to convert from in the left box containing the list of units. Select the unit to convert to in the right box containing the list of units. Enter the value (for example “15”) into the left From box. The result will appear in the Result box and in the To box. Alternatively, you can enter the value into the right To box and read the result of conversion in the From and Result boxes. If you have noticed an error in the text or calculations, or you need another converter, which you did not find here, please let us know ! Convert nanocoulomb [nC] <—> coulomb [C] • Electrical Engineering • Electric Charge • Compact Calculator Learn technical English with this video!

Overview This may sound surprising, but we encounter static electricity daily — when stroking our cat, brushing our hair, or putting on a sweater made of synthetic materials. We thus become static electricity generators. We are actually “enveloped” in static electricity every day, because we live in the strong electrostatic field of the Earth. This field is generated because the Earth is surrounded by the upper layer of the atmosphere, the ionosphere, which conducts electricity. Ionosphere was formed under the influence of the cosmic radiation, and has its own charge. While engaging in everyday activities such as warming up food, we generally do not think that we are essentially using static electricity when igniting the gas on the gas burner with automatic ignition or with an electric lighter. Examples of Static Electricity Lightning on Earth. View from the International Space Station. Photographs by NASA. As children and sometimes into adulthood, we are afraid of thunder, even though thunder by itself is harmless and is merely the nature’s “sound effect” to lightning — a fascinating display caused by the static electricity in the atmosphere. It is simply our instinct to fear thunder — this fear makes us aware of the dangers of the lightning. Lightning is not the only such phenomenon that generates both fear and fascination.

In the past when sailboats were common, sailors were awe-struck by St. Elmo’s fire on the masts of their sailboats, caused by static electricity in the atmosphere. Electricity had its place in mythology as well — people associated lightning with ancient gods: Greek Zeus, Roman Jupiter, Scandinavian Thor, or Slavic Perun. An Air Canada aircraft is grounded while being refueled People have been fascinated with electricity for many centuries, and we often do not realize that the scientists, who studied static electricity and came to many useful conclusions about its properties, saved us from the horrors of fires and explosions. We have tamed static electricity by using lightning rods for our buildings and grounding devices to ensure safety of fuel trucks. Despite this, static electricity continues to disrupt our daily life by creating interference with radio signals. This is not surprising: at each instant in time there are up to 2000 thunderstorms that generate up to 50 lightnings per second. People have been studying static electricity since ancient times. Even the word “electron” came to us from Ancient Greek, although it did not have the current meaning back then.

Instead it meant amber — a material that electrifies really well when rubbed (ancient Greek ἤλεκτρον — amber). Unfortunately, the study of static electricity had victims: while conducting experiments Georg Wilhelm Richmann, a Russian scientist, was killed by lightning, the most deadly phenomenon caused by static electricity. Static Electricity and the Weather Generally speaking the mechanism by which the storm cloud gathers an electric charge is very similar to the process of electrification of a hair brush — charging in both cases happens due to friction. Ice particles in the cloud are formed from the water drops, as they are moved from the lower and warmer layers of the atmosphere up to the colder ones. These ice particles collide as they move. Bigger particles become negatively charged, while the smaller ones get a positive charge. The weight difference of the particles causes the movement of particles within the cloud, with the heavier ones gathering at the bottom and the lighter smaller ones — at the top of the cloud. This movement is called an updraft. Even though the cloud as a whole is neutrally charged, the bottom of it is charged negatively, and the top — positively.

Benjamin Franklin on the $100 bill Just as the electrified hair brush attracts a balloon because the electric charge is concentrated on the side of it that is closer to the brush, so does the storm cloud, which creates a positive charge on the surface of the Earth. As the cloud develops into a storm cloud, the charge grows, and the field density increases. Once this density reaches a critical point for the given weather conditions, an electrostatic discharge, that is, lightning, occurs. Trust in God, but ground your house! Humanity owes the invention of the lightning rod to Benjamin Franklin, a scientist who later became the President of Pennsylvania, and first U.S. Postmaster General. Since his invention the number of fires, caused by the lightning striking buildings has been mostly eradicated. Franklin decided not to patent his invention, making it available for all people on the planet. Sometimes lightnings can be useful. For example, historically iron and copper mining specialists that worked in the Ural mines in Russia determined the presence of these ores by the frequency of lightning strikes in a given area. Leyden jars. Canada Science and Technology Museum.

When talking about scientists that studied electrostatic phenomena, it is important to remember the British physicist Michael Faraday, the father of electrodynamics, as well as the Dutch scientist Pieter van Musschenbroek, the inventor of the prototype of a capacitor — the famous Leyden jar. While watching car races such as the Deutsche Tourenwagen Masters (DTM), IndyCar, or Formula 1, we often do not realize that car mechanics choose whether or not to use rain tires based on the information collected by the local weather radars. This data is in turn based on the electrical characteristics of the clouds above the area. Weather radar at Toronto Pearson airport Static electricity is both our friend and our foe. Electrical engineers have to work around it. Lightning can damage circuit boards located in the vicinity of the strike — usually it is their input stages that are damaged in this event. The engineers have to use grounding straps when fixing these circuit boards. When the grounding equipment does not operate as expected, it can cause serious accidents and even catastrophes with numerous casualties, from fires to explosions of entire factories.

Static Electricity in Medicine Despite numerous problems that static electricity causes, it helps people with life-threatening ventricular fibrillation, which is a condition in which there are chaotic contractions of the heart muscle. The heart can be restored to normal functioning by subjecting it to a small electrostatic charge. This is done by a device called the defibrillator. It is important to note that this device does not restart the heart but stops the incorrect rhythm and is used along with other treatments. The scene depicting the “return to life” of a patient with acute heart failure by using a defibrillator is a classic for movies of a certain genre. The movies often make a mistake of showing the revival of a patient with no heartbeat (as seen by the straight line on the monitor) by using the defibrillator. This is incorrect — the defibrillator cannot “restart” a heart. Static dischargers on the wing of a Boeing 738-800 are designed to control corona discharge into the atmosphere and providing reliable work of aircraft onboard navigation and communication equipment Other Examples We should not forget about the necessity to connect all separate components of an airplane together by bonding strips to protect them from static electricity.

To do so all of the metal parts in the airplane including the engine are connected to each other to make an electrically-integral structure. All trailing edges of wings, flaps, ailerons, elevator and the rudder of the airplane are outfitted with static dischargers to ensure that the static electricity, generated during the flight as a consequence of friction between the airplane and the air, is discharged into the air. This reduces the interference from static electricity with the work of the onboard electronic devices. Electrostatic experiments are some of the most exciting in the section on electricity of the high school Physics courses: there are the hair standing straight up, the balloons that chase hair brushes, the mysterious glow of fluorescent lights not connected to the power source, and many more! This glow saves lives of electricians working with high voltage power lines and power distribution units. The most important aspect of static electricity is its role in the life on Earth. Scientists came to believe that it is thanks to electrostatics that the life as we know it emerged.

Early experiments in the mid-20th century showed that sending an electrical charge through a mix of gases similar to the mix present in the atmosphere of the Earth around the time when life emerged, generates an amino acid, which is one of the building blocks of life. Uninterruptible power supply units or UPS are used to safeguard against loss of power or power surges such as those that can happen during the lightning strike. In order to tame static electricity it is important to know the difference of potentials or the electric voltage. Devices called voltmeters have been invented for this purpose. The notion of electric voltage was introduced by the 19th century Italian scientist Alessandro Volta, and the units that measure voltage were called “volts” after him. Before the invention of voltmeters, different devices called galvanometers were used to measure electrostatic voltage. The term “galvanometer” was derived from the surname of another Italian scientist, Luigi Galvani. Unfortunately, the measuring mechanism of an electrodynamic system used in galvanometers distorted the measurements. Study of Static Electricity It is believed that the systematic study of electrostatics started in the 18th century with the work of the French scientist Charles-Augustin de Coulomb.

In particular, he was the one who introduced the notion of electric charge and formulated the law that describes the interaction between electric charges. The unit that quantifies the amount of electricity, namely the electrical charge, is named coulomb (C) after him. To be fair we should mention that a British scientist Henry Cavendish also worked on similar problems before Coulomb, but he did not publish this work during his lifetime — it was published by his heirs about 100 years later. Earlier work on electricity allowed physicists George Green, Carl Friedrich Gauss, and Siméon Denis Poisson to create an elegant mathematical model for electricity. We use it till this day. This model is based on the concept of an electron, which is a subatomic particle. Every atom contains electrons and they can be easily separated from the atomic structure when external forces are applied. The principle of repulsion of similarly charged particles and attraction of particles with opposite charges is also fundamental in our understanding of electricity. Measuring Electrical Values Digital multimeter can measure current, voltage, resistance and check transistors One of the first devices used to quantify electricity was developed by the British physicist Abraham Bennet. It consisted of two pieces of gold foil inside a glass container.

Since then, measuring devices have greatly improved, and now they can measure in units as small as nanocoulombs (nC). Using very precise measuring devices, the Russian physicist Abram Ioffe and the American physicist Robert Andrews Millikan were able to measure the electric charge of an electron. With the development of digital technologies, highly sensitive measuring devices were built. They have unique characteristics, which allow them to work with minimal and almost undetectable distortions. This is due to their high input resistance. Besides measuring voltage, these devices can measure other important characteristics at a wide measurement range, such as ohmic resistance and the flow of electric current. The most advanced devices are called multimeters or multitesters for their range of functionality. They also measure the frequency of alternating current and capacitance of capacitors. In addition they allow the user to test transistors and even to measure temperature. Generally, modern devices have safety features that prevent the device from breaking if it is used incorrectly. They are small and easy to use. They are also safe — the safety is checked under strenuous work conditions using a battery of tests. They are also tested for accuracy. At the end of the tests the device receives a certificate indicating its safety and accuracy.

This article was written by Sergey Akishkin You can hide articles if you use this converter often. Cookies must be allowed in your browser. You may be interested in another converters in the Electrical Engineering group: Learn Technical English with Our Videos! You can use this online converter to convert between several hundred units (including metric, British and American) in 76 categories, or several thousand pairs including acceleration, area, electrical, energy, force, length, light, mass, mass flow, density, specific volume, power, pressure, stress, temperature, time, torque, velocity, viscosity, volume and capacity, volume flow, and more. Note: Integers (numbers without a decimal period or exponent notation) are considered accurate up to 15 digits and the maximum number of digits after the decimal point is 10. In this calculator, E notation is used to represent numbers that are too small or too large. E notation is an alternative format of the scientific notation a · 10x. For example: 1,103,000 = 1.103 · 106 = 1.103E+6.

Here E (from exponent) represents “· 10^”, that is “times ten raised to the power of”. E-notation is commonly used in calculators and by scientists, mathematicians and engineers. Select the unit to convert from in the left box containing the list of units. Select the unit to convert to in the right box containing the list of units. Enter the value (for example “15”) into the left From box. The result will appear in the Result box and in the To box. Alternatively, you can enter the value into the right To box and read the result of conversion in the From and Result boxes. If you have noticed an error in the text or calculations, or you need another converter, which you did not find here, please let us know ! Electrical units of measurment (V,A,Ω,W,...) Volt (V) Volt is the electrical unit of voltage . One volt is the energy of 1 joule that is consumed when electric charge of 1 coulomb flows in the circuit. 1V = 1J / 1C Ampere (A) Ampere is the electrical unit of electrical current .

It measures the amount of electrical charge that flows in an electrical circuit per 1 second. 1A = 1C / 1s Ohm is the electrical unit of resistance. 1Ω = 1V / 1A Watt is the electrical unit of electric power . It measures the rate of consumed energy. 1W = 1J / 1s 1W = 1V ï¿½ 1A Decibel-milliwatt (dBm) Decibel-milliwatt or dBm is a unit of electric power , measured with logarithmic scale referenced to 1mW. 10dBm = 10 ï¿½ log10(10mW / 1mW) Decibel-Watt (dBW) Decibel-watt or dBW is a unit of electric power , measured with logarithmic scale referenced to 1W. 10dBW = 10 ï¿½ log10(10W / 1W) Farad (F) Farad is the unit of capacitance. It represents the amount of electric charge in coulombs that is stored per 1 volt.

1F = 1C / 1V Henry is the unit of inductance. 1H = 1Wb / 1A siemens is the unit of conductance, which is the opposite of resistance. 1S = 1 / 1Ω Coulomb is the unit of electric charge . 1C = 6.238792×1018 electron charges Ampere-hour (Ah) Ampere-hour is a unit of electric charge . One ampere-hour is the electric charge that flow in electrical circuit, when a current of 1 ampere is applied for 1 hour. 1Ah = 1A ï¿½ 1hour One ampere-hour is equal to 3600 coulombs. 1Ah = 3600C Tesla is the unit of magnetic field. 1T = 1Wb / 1m2 Weber is the unit of magnetic flux. 1Wb = 1V ï¿½ 1s Joule (J) Joule is the unit of energy. 1J = 1 kg ï¿½ 1(m / s)2 Kilowatt-hour (kWh) Kilowatt-hour is a unit of energy.

1kWh = 1kW ï¿½ 1h = 1000W ï¿½ 1h Kilovolt-amps (kVA) Kilovolt-amps is a unit of power. 1kVA = 1kV ï¿½ 1A = 1000 ï¿½ 1V ï¿½ 1A Hertz (Hz) Hertz is the unit of frequency. It measures the number of cycles per second. 1 Hz = 1 cycles / s Electrical capacitance | Article about Electrical capacitance by The Free Dictionary Electrical capacitance | Article about Electrical capacitance by The Free Dictionary Related to Electrical capacitance: electrical resistance , Electrical inductance , Electrical capacitor capacitance, in electricity, capability of a body, system, circuit, or device for storing electric charge. Capacitance is expressed as the ratio of stored charge in coulombs to the impressed potential difference in volts. The resulting unit of capacitance is the farad farad [for Michael Faraday], unit of electrical capacitance, equivalent to 1 coulomb of stored charge per volt of applied potential difference. ..... Click the link for more information.

[for Michael Faraday Faraday, Michael , 1791–1867, English scientist. The son of a blacksmith, he was apprenticed to a bookbinder at the age of 14. He had little formal education, but acquired a store of scientific knowledge through reading and by attending educational lectures including, in ..... Click the link for more information. ]. In an electric circuit the device designed to store charge is called a capacitor capacitor or condenser, device for the storage of electric charge. Simple capacitors consist of two plates made of an electrically conducting material (e.g., a metal) and separated by a nonconducting material or dielectric (e.g. ..... Click the link for more information. . An ideal capacitor, i.e., one having no resistance or inductance, may be spoken of as a capacitance. When an alternating current flows through a capacitor, the capacitor produces a reactance that resists the current (see impedance impedance, in electricity, measure in ohms of the degree to which an electric circuit resists the flow of electric current when a voltage is impressed across its terminals. ..... Click the link for more information. ).

While every element of a circuit has some capacitance, it is a goal of good design to reduce such unwanted or stray capacitance to a minimum. Capacitance The ratio of the charge q on one of the plates of a capacitor (there being an equal and opposite charge on the other plate) to the potential difference v between the plates; that is, capacitance (formerly called capacity) is C = q/v. In general, a capacitor, often called a condenser, consists of two metal plates insulated from each other by a dielectric. The capacitance of a capacitor depends on the geometry of the plates and the kind of dielectric used, since these factors determine the charge which can be put on the plates by a unit potential difference existing between the plates. In an ideal capacitor, no conduction current flows between the plates. A real capacitor of good quality is the circuit equivalent of an ideal capacitor with a very high resistance in parallel or, in alternating-current (ac) circuits, of an ideal capacitor with a low resistance in series. See Capacitor , Dielectric materials Capacitance a quantitative measure of a conductor’s ability to hold an electric charge. In an electrostatic field, all points of a conductor are at the same potential φ.

If infinity is taken as the zero point for potential, φ is proportional to the charge q on the conductor; that is, the ratio of q to φ is not a function of q. The capacitance C of an isolated conductor is equal to the ratio of the charge on the conductor to the conductor’s potential: C = q/φ. Thus, the greater the capacitance, the greater the charge that can be stored by the conductor at a given φ. Capacitance is determined by the size and shape of a conductor and by the electrical properties of the surrounding medium, that is, by the medium’s dielectric constant. Capacitance does not depend on the material of the conductor. Specifically, in the centimeter-gram-second (cgs) electrostatic system, the capacitance of a conducting sphere in vacuo is equal to the radius of the sphere. Since the potential of a conductor also depends on the electric fields created by the charges induced in the surrounding bodies as a result of electrostatic induction, the presence of bodies near a conductor changes its capacitance.

Capacitance is measured in centimeters in the cgs system and in farads (1 farad = 9 × 1011 cm) in the International System of Units (SI). The concept of capacitance applies not only to a single conductor but also to systems of conductors. It applies in particular to a system of two conductors that are separated by a thin dielectric layer. Such a system is called a capacitor. The capacitance of a capacitor is expressed by the equation C = q/(φ1 – φ2). where q is the charge on one plate, –q is the charge on the other plate, and φ1 – φ2 is the potential difference between the plates. The capacitance of a capacitor is virtually independent of the presence of surrounding bodies and can be very high in capacitors with small dimensions. REFERENCE farad - definition and meaning farad Definitions from The American Heritage® Dictionary of the English Language, 4th Edition n. The unit of capacitance in the meter-kilogram-second system equal to the capacitance of a capacitor having an equal and opposite charge of 1 coulomb on each plate and a potential difference of 1 volt between the plates. See Table at measurement.

from Wiktionary, Creative Commons Attribution/Share-Alike License n. In the International System of Units, the derived unit of electrical capacitance; the capacitance of a capacitor in which one coulomb of charge causes a potential difference of one volt across the capacitor. Symbol: F from the GNU version of the Collaborative International Dictionary of English n. The standard unit of electrical capacity; the capacity of a condenser whose charge, having an electro-motive force of one volt, is equal to the amount of electricity which, with the same electromotive force, passes through one ohm in one second; the capacity, which, charged with one coulomb, gives an electro-motive force of one volt. from The Century Dictionary and Cyclopedia n. The electromagnetic unit of capacity of electricity. from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved. n. the capacitance of a capacitor that has an equal and opposite charge of 1 coulomb on each plate and a voltage difference of 1 volt between the plates Etymologies from The American Heritage® Dictionary of the English Language, 4th Edition After Michael Faraday.

from Wiktionary, Creative Commons Attribution/Share-Alike License Named after the English physicist Michael Faraday. Examples Much is riding on the outcome: the joule, watt, volt, farad, weber and ohm are only some of the units derived in part from the kilo. Electric capacitance | Article about Electric capacitance by The Free Dictionary Electric capacitance | Article about Electric capacitance by The Free Dictionary Also found in: Dictionary , Thesaurus , Medical , Wikipedia . capacitance, in electricity, capability of a body, system, circuit, or device for storing electric charge. Capacitance is expressed as the ratio of stored charge in coulombs to the impressed potential difference in volts. The resulting unit of capacitance is the farad farad [for Michael Faraday], unit of electrical capacitance, equivalent to 1 coulomb of stored charge per volt of applied potential difference. ..... Click the link for more information. [for Michael Faraday Faraday, Michael , 1791–1867, English scientist. The son of a blacksmith, he was apprenticed to a bookbinder at the age of 14.

He had little formal education, but acquired a store of scientific knowledge through reading and by attending educational lectures including, in ..... Click the link for more information. ]. In an electric circuit the device designed to store charge is called a capacitor capacitor or condenser, device for the storage of electric charge. Simple capacitors consist of two plates made of an electrically conducting material (e.g., a metal) and separated by a nonconducting material or dielectric (e.g. ..... Click the link for more information. . An ideal capacitor, i.e., one having no resistance or inductance, may be spoken of as a capacitance. When an alternating current flows through a capacitor, the capacitor produces a reactance that resists the current (see impedance impedance, in electricity, measure in ohms of the degree to which an electric circuit resists the flow of electric current when a voltage is impressed across its terminals. ..... Click the link for more information. ). While every element of a circuit has some capacitance, it is a goal of good design to reduce such unwanted or stray capacitance to a minimum.

Capacitance The ratio of the charge q on one of the plates of a capacitor (there being an equal and opposite charge on the other plate) to the potential difference v between the plates; that is, capacitance (formerly called capacity) is C = q/v. In general, a capacitor, often called a condenser, consists of two metal plates insulated from each other by a dielectric. The capacitance of a capacitor depends on the geometry of the plates and the kind of dielectric used, since these factors determine the charge which can be put on the plates by a unit potential difference existing between the plates. In an ideal capacitor, no conduction current flows between the plates. A real capacitor of good quality is the circuit equivalent of an ideal capacitor with a very high resistance in parallel or, in alternating-current (ac) circuits, of an ideal capacitor with a low resistance in series. See Capacitor , Dielectric materials Capacitance a quantitative measure of a conductor’s ability to hold an electric charge. In an electrostatic field, all points of a conductor are at the same potential φ.

If infinity is taken as the zero point for potential, φ is proportional to the charge q on the conductor; that is, the ratio of q to φ is not a function of q. The capacitance C of an isolated conductor is equal to the ratio of the charge on the conductor to the conductor’s potential: C = q/φ. Thus, the greater the capacitance, the greater the charge that can be stored by the conductor at a given φ. Capacitance is determined by the size and shape of a conductor and by the electrical properties of the surrounding medium, that is, by the medium’s dielectric constant. Capacitance does not depend on the material of the conductor. Specifically, in the centimeter-gram-second (cgs) electrostatic system, the capacitance of a conducting sphere in vacuo is equal to the radius of the sphere. Since the potential of a conductor also depends on the electric fields created by the charges induced in the surrounding bodies as a result of electrostatic induction, the presence of bodies near a conductor changes its capacitance.

Capacitance is measured in centimeters in the cgs system and in farads (1 farad = 9 × 1011 cm) in the International System of Units (SI). The concept of capacitance applies not only to a single conductor but also to systems of conductors. It applies in particular to a system of two conductors that are separated by a thin dielectric layer. Such a system is called a capacitor. The capacitance of a capacitor is expressed by the equation C = q/(φ1 – φ2). where q is the charge on one plate, –q is the charge on the other plate, and φ1 – φ2 is the potential difference between the plates. The capacitance of a capacitor is virtually independent of the presence of surrounding bodies and can be very high in capacitors with small dimensions. REFERENCE Molecular Expressions: Electricity and Magnetism - Capacitance Discover how the discharging of a natural capacitor causes lightning. Capacitors are used in many ways in electronic circuits, such as barriers to direct currents, storing memory in a computer chip, storing a charge for an electronic flash camera, or adjusting a tuned circuit such as in a radio.

Description of a Capacitor A capacitor in its simplest form consists of two conducting plates separated by an insulating layer called a dielectric. When a capacitor is connected in a circuit across a voltage source, the voltage forces electrons onto the surface of one plate and pulls electrons off the surface of the other plate resulting in a potential difference between the plates. Capacitors are charged and discharged as needed by its application. Capacitors differ in size and arrangements of plates and the type of dielectric materials used. Paper, ceramic, air, mica, and electrolytic materials can be used, depending on the type of dielectric needed. The capacitance of a capacitor may be fixed or adjustable (as in a radio tuner). Charging of a Capacitor When a capacitor is connected across a voltage source, such as a battery, the voltage forces electrons onto one plate resulting in a negatively charged plate. The electrons of the other plate are pulled off by the battery resulting in a positively charged plate. Because the dielectric between the plates is an insulator, current cannot flow through it. A capacitor has a finite amount of capacity to store charges. When a capacitor reaches its capacity it is fully charged. The following diagrams illustrate the charging of a capacitor.

Figure 2 shows a circuit containing a conductor connecting a battery, an open switch, and a capacitor. The capacitor in Figure 2 is not charged. There is no potential difference between the plates. When the switch is closed, as in Figure 3, there is a momentary surge of current through the conductor to and from the plates of the capacitor. When the current reaches the negative plate of the capacitor, it is stopped by the dielectric. The surge of electric current to the capacitor induces a counter electromotive force in the conductor and the plates. This counter electromotive force is call reactance. When reactance has reached a level equal to the voltage of the battery, the capacitor is fully charged. There is no further flow of current. When the capacitor is fully charged, the switch may be opened and the capacitor will retain its charge (Figure 4). Because of the difference of charges on the plates there is a source of potential energy in the capacitor. The energy stored is the energy that was required to charge the capacitor. The lines of force between the plates of the capacitor represent an electric force field (see Figures 3 and 4). This electric force field exists because of the unequal charges, positive and negative, on the inside surfaces of the plates.

Current cannot flow through the electrostatic field because of the dielectric insulator. In other words, the difference in potential between the plates induces within the dielectric an electrostatic field that retains the charge. Discharging of a Capacitor The charged capacitor shown in Figure 4 is now a source of potential energy. This potential energy is now available for its intended electronic application. If the switch is closed, as in Figure 5, current will immediately begin to flow through from the negative plate to the positive plate. The capacitor is discharging. The charged capacitor is the source of voltage for the current flow. The current will cease flowing when the charges of the two plates are again equal, meaning that the capacitor is completely discharged. We have simulated the charging and discharging of a capacitor in our Capacitor Interactive Java Tutorial. Interactive Java Tutorial Discover how a capacitor is charged and discharged. Dielectric Materials The dielectric material in a capacitor prevents the flow of current between its plates. It also serves as a medium to support the electrostatic force of a charged capacitor. A variety of materials are used for dielectrics as shown in the chart below. Dielectric materials are rated based upon their ability to support electrostatic forces in terms of a number called a dielectric constant.

The ability of the dielectric to support electrostatic forces is directly proportional to the dielectric constant. A vacuum is the standard by which other dielectrics are rated. The dielectric constant of a vacuum is 1. You can see from the chart that there is very little difference in the dielectric constant of a vacuum and air. Therefore, air is often referred to as having a dielectric constant of 1. Material 81 Measurement of Capacitance Capacitance is measured in farads, which is named after Michael Faraday (1791-1867). The symbol for farads is F. If a charge of 1 coulomb is placed on the plates of a capacitor and the potential difference between them is 1 volt, the capacitance is then defined to be 1 farad. One coulomb is equal to the charge of 6.25 x 1018 electrons. One farad is an extremely large quantity of capacitance. Microfarads (10-6 F) and picofarads (10-12 F) are more commonly used.

The capacitance of a capacitor is proportional to the quantity of charge that can be stored in it for each volt difference in potential between its plates. Mathematically this relationship is written as: C = Q/V Where C is capacitance in farads, Q is the quantity of stored electrical charge in coulombs, and V is the difference in potential in volts. Therefore, stored electric charge can be calculated using the formula: Q = CV Factors Affecting Value of Capacitance The capacitance of a capacitor is affected by three factors: The area of the plates The distance between the plates The dielectric constant of the material between the plates Larger plates provide greater capacity to store electric charge. Therefore, as the area of the plates increase, capacitance increases. Capacitance is directly proportional to the electrostatic force field between the plates. This field is stronger when the plates are closer together. Therefore, as the distance between the plates decreases, capacitance increases. As the distance between the plates increases, capacitance decreases. As discussed above, the ability of the dielectric to support electrostatic forces is directly proportional to the dielectric constant. Therefore, as the dielectric constant increases, capacitance increases.

Taking into account each of the above three factors, the capacitance of a capacitor with two parallel plates can be calculated using the formula: C = (8.855KA) ÷ d Where C is capacitance in picofarads, K is the dielectric constant, A is the area of one plate in m2, and d is the distance between plates in m. Our Factors Affecting Capacitance Interactive Java Tutorial demonstrates changes of capacitance as plate size, distance, and dielectric constants are adjusted. Interactive Java Tutorial Discover the factors affecting capacitance. Resistive-Capacitive Series Circuits and Time Constant As a capacitor becomes charged, the current flow decreases because the voltage developed by the capacitor increases over time and opposes the source voltage. Therefore, the rate of charge of a capacitor is reduced over time. The amount time required to charge and discharge a capacitor is a very important factor in the design of electronic circuits. Resistors are often used in combination with capacitors in order to control the charge and discharge time necessary for the intended application. Resistance directly affects the time required to charge a capacitor. As resistance increases, it takes more time to charge a capacitor.

The amount of time for the capacitor to become fully charged in a resistive-capacitive (RC) circuit depends on the values of the capacitor and resistor. The following graph shows the rate of charge of a capacitor in a RC circuit. Note that the rate of charge greatly decreases over time. The latter part of its charging time is many times longer than the first part. In fact, a capacitor reaches 63.2% of its charge in one fifth of the time it takes to become fully charged. Because of this, capacitors in actual applications are generally not fully charged. Capacitors in circuits are generally charged to just 63.2% of full capacity. The time required for a capacitor to charge to 63.2% of its full capacity is referred as its RC (resistive-capacitive) time constant. It is important to know how to calculate RC time constants in order to design many different kinds of electronic circuits. The RC time constant of a circuit can be calculated by using the following formula: t = C x R Where t is time in seconds, C is capacitance in farads, and R is resistance in ohms.

Our RC Time Constant Interactive Java Tutorial demonstrates changes in the RC time constant as values of resistance and capacitance are adjusted. Interactive Java Tutorial Observe changes in the RC time constant for different values of resistance and capacitance. Capacitors in Parallel Circuits Capacitance can be increased in a circuit by connecting capacitors in parallel as shown in the following diagram: We know that capacitance of a capacitor can be increased by increasing the size of its plates. Connecting two or more capacitors in parallel in effect increases plate size. Increasing plate area makes it possible to store more charge and therefore creating greater capacitance. To determine total capacitance of several parallel capacitors, simply add up their individual values. The following is the formula for calculating total capacitance in a circuit containing capacitors in parallel: CT = C1 + C2 + C3 . . . Capacitors in Series Circuits Capacitance can be decreased in a circuit by capacitors in series as shown in the following diagram: We know that capacitance of a capacitor can be decreased by placing the plates further apart. Connecting two or more capacitors in series in effect increases the distance between the plates and thickness of the dielectric, thereby decreasing the amount of capacitance.

The following is the formula for calculating total capacitance in a circuit containing two capacitors in series: CT = (C1 x C2x C3) / (C1 + C2+ C3) Voltage Rating of Capacitors In selecting an appropriate capacitor for a given application, consideration must be made not only for value of capacitance, but also for the amount of voltage the capacitor will be subject to. Capacitors are designed to withstand a certain maximum voltage. Exceeding the maximum voltage may result in current arcing through the dielectric and damaging the capacitor. The maximum voltage that a capacitor can withstand is its working voltage. The manufacturer indicates the working voltage. However, the standard margin of error is to select a capacitor with a working voltage that is 50 percent higher than the maximum voltage that will be used in the application. Variable Capacitors There are two major types of capacitors: fixed and variable. The fixed capacitor has a specific value of capacitance. A variable capacitor allows for a range of capacitance. Variable capacitors are designed so that capacitance can be changed through a mechanical means such as adjusting a screw or turning a shaft.

Variable capacitors are used when the application requires an adjustment of capacitance such as in a radio tuner. Below is a typical variable capacitor. It has two sets of plates. One set is called the rotor and the other the stator. The rotor is usually connected to a knob outside the capacitor. The two sets of plates are close together but not touching. Air is the dielectric in a variable capacitor. As the knob is turned, the sets of plates become more or less meshed, increasing or decreasing the distance between the plates. As the plates become more meshed, capacitance increases. As the plates become less meshed, capacitance decreases. Capacitors in Action Computer Memory In most cases, the main memory of a computer is a high-speed random-access memory (RAM). Two types of main memory are possible with RAM circuits, static random-access memory (SRAM) and dynamic random-access memory (DRAM). A single memory chip is made up of several million memory cells. In a SRAM chip, each memory cell consists of a resistor circuit flip-flop for storing the binary digits 1 or 0. In a DRAM chip, each memory cell consists of a capacitor rather than a resistor circuit flip-flop.

When a capacitor is electrically charged, it is said to store the binary digit 1, and when discharged, it represents 0. Figure 10 below shows a portion of a memory chip containing 16 memory cells. Condenser Microphones A microphone converts sound waves into an electric signal. All microphones have a diaphragm that vibrates as sound waves strike. The vibrating diaphragm in turn causes an electrical component to create an output flow of current at a frequency proportional to the sound waves. A condenser microphone uses a capacitor for this purpose. In a condenser microphone the diaphragm is the negatively charged plate of a charged capacitor. When a sound wave compresses the diaphragm, the diaphragm is moved closer to the positive plate. Decreasing the distance between the plates increases the electrostatic attraction between them. This results in a flow of current to the negative plate. As the diaphragm moves out in response to sound waves, the diaphragm moves further from the positive plate. Increasing the distance between the plates decreases the electrostatic attraction between them. This results in a flow of current back to the positive plate.

These alternating flows of current provide weak electronic signals which travel to a mixer, then to an amplifier, and finally to a loudspeaker. You can observe the operation of a condenser microphone at our Condenser Microphone Java Tutorial. Interactive Java Tutorial Discover how a microphone works. Radio Receiver Variable capacitors are used in tuning circuits of radios. In Figure 11, a variable capacitor is connected to an antenna-transformer circuit. Transmitted radio waves cause an induced current to flow in the antenna through the primary coil to ground. A secondary current in the opposite direction is induced in the secondary coil. This current flows to the capacitor. We know that the surge of current to the capacitor induces a counter electromotive force. This counter electromotive force is call reactance. The induced flow of current through the coil also induces a counter electromotive force. This is called inductive reactance. So we have both capacitive and inductive reactance. At higher frequencies, inductive reactance is greater and capacitive reactance is smaller. At lower frequencies the opposite is true. A variable capacitor is used to equalize the inductive and capacitive reactances. The condition in which the reactances are equalized is called resonance.

The particular frequency that is isolated by the equalized reactances is called the resonant frequency. A radio circuit is tuned by adjusting the capacitance of a variable capacitor to equalize the inductive and capacitive reactance of the circuit for the desired resonant frequency, or in other words, to tune in the desired radio station. Our Radio Receiver Interactive Java Tutorial demonstrates how a variable capacitor is used to tune in radio frequencies. Interactive Java Tutorial Discover how a variable capacitor is used to tune in radio frequencies. Pulsed Magnets At the National High Magnetic Field Laboratory, magnets are used for research in all areas of science, including biology, chemistry, geology, engineering, material science, and physics. Research in high magnetic fields is critical because it allows scientists to study matter at the molecular level. One type of magnet used is a pulsed magnet. Pulsed magnets are capable of inducing magnetic fields as high as 800 teslas. In order to generate such high fields, extremely high electrical currents are required, often in the tens of thousands of amps. Pulsed magnets are usually powered by a capacitor bank, a device containing a large number of capacitors capable of storing massive amounts of electrical energy.

The capacitor bank is discharged in a fraction of a second through the coil of the magnet. Typical energies are of the order of 0.5 to 1 megajoules. We have simulated the powering of a pulsed magnet in our Pulsed Magnet Interactive Java Tutorial . Interactive Java Tutorial

Question: What is the electrical capacitance which 1 coulomb of electricity will charge to a capacity of 1 volt?
Answer: Farad