Dielectric barrier discharge
Dielectric-barrier discharge is the electrical discharge between two electrodes separated by an insulating dielectric barrier. Originally called silent discharge and known as ozone production discharge or partial discharge, on right, the schematic diagram shows a typical construction of a DBD wherein one of the two electrodes is covered with a dielectric barrier material. The lines between the dielectric and the electrode are representative of the filaments, which are normally visible to the naked eye. Below this, the shows a atmospheric DBD discharge occurring in between two steel electrode plates, each covered with a dielectric sheet. The filaments are columns of conducting plasma, and the foot of each filament is representative of the accumulated charge. The process normally uses high voltage alternating current, ranging from lower RF to microwave frequencies, other methods were developed to extend the frequency range all the way down to the DC. One method was to use a high resistivity layer to cover one of the electrodes and this is known as the resistive barrier discharge.
In a common configuration, the dielectric is shaped in the same form as common fluorescent tubing. It is filled at atmospheric pressure with either a gas or rare gas-halide mix. Due to the pressure level, such processes require high energy levels to sustain. Common dielectric materials include glass, quartz and polymers, the gap distance between electrodes varies considerably, from less than 0.1 mm in plasma displays, several millimetres in ozone generators and up to several centimetres in CO2 lasers. Depending on the geometry, DBD can be generated in a volume or on a surface, for VDBD the plasma is generated between two electrodes, for example between two parallel plates with a dielectric in between. The plasma is generated on top of the surface of an SDBD plate, a particular compact and economic DBD plasma generator can be built based on the principles of the piezoelectric direct discharge. In this technique, the voltage is generated with a piezo-transformer. Since the transformer material is a dielectric, the electric discharge resembles properties of the dielectric barrier discharge. A multitude of random arcs form in operation gap exceeding 1.5 mm between the two electrodes during discharges in gases at the atmospheric pressure, as the charges collect on the surface of the dielectric, they discharge in microseconds, leading to their reformation elsewhere on the surface.
Such recombinations are directly proportional to the collisions between the molecules and in turn to the pressure of the gas, as explained by Paschens Law. The discharge process causes the emission of a photon, the frequency
Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. With an electronic sensor, this produces an electrical charge at each pixel. A negative image on film is used to photographically create a positive image on a paper base, known as a print. The word photography was created from the Greek roots φωτός, genitive of φῶς, light and γραφή representation by means of lines or drawing, several people may have coined the same new term from these roots independently. Johann von Maedler, a Berlin astronomer, is credited in a 1932 German history of photography as having used it in an article published on 25 February 1839 in the German newspaper Vossische Zeitung. Both of these claims are now widely reported but apparently neither has ever been confirmed as beyond reasonable doubt. Credit has traditionally given to Sir John Herschel both for coining the word and for introducing it to the public.
Photography is the result of combining several technical discoveries, Greek mathematicians Aristotle and Euclid independently described a pinhole camera in the 5th and 4th centuries BCE. Daniele Barbaro described a diaphragm in 1566, wilhelm Homberg described how light darkened some chemicals in 1694. The fiction book Giphantie, published in 1760, by French author Tiphaigne de la Roche, the discovery of the camera obscura that provides an image of a scene dates back to ancient China. Leonardo da Vinci mentions natural camera obscura that are formed by dark caves on the edge of a sunlit valley, a hole in the cave wall will act as a pinhole camera and project a laterally reversed, upside down image on a piece of paper. So the birth of photography was primarily concerned with inventing means to capture, renaissance painters used the camera obscura which, in fact, gives the optical rendering in color that dominates Western Art. The camera obscura literally means dark chamber in Latin and it is a box with a hole in it which allows light to go through and create an image onto the piece of paper.
Around the year 1800, British inventor Thomas Wedgwood made the first known attempt to capture the image in a camera obscura by means of a light-sensitive substance and he used paper or white leather treated with silver nitrate. The shadow images eventually darkened all over, the first permanent photoetching was an image produced in 1822 by the French inventor Nicéphore Niépce, but it was destroyed in a attempt to make prints from it. Niépce was successful again in 1825, in 1826 or 1827, he made the View from the Window at Le Gras, the earliest surviving photograph from nature. Because Niépces camera photographs required a long exposure, he sought to greatly improve his bitumen process or replace it with one that was more practical. With an eye to eventual commercial exploitation, the partners opted for total secrecy, Daguerres efforts culminated in what would be named the daguerreotype process
Space charge is a concept in which excess electric charge is treated as a continuum of charge distributed over a region of space rather than distinct point-like charges. Space charge usually only occurs in dielectric media because in a medium the charge tends to be rapidly neutralized or screened. The sign of the charge can be either negative or positive. This situation is perhaps most familiar in the area near an object when it is heated to incandescence in a vacuum. The resulting cloud is negatively charged, and can be attracted to any nearby positively charged object, water tree is a name given to a tree-like figure appearing in a water-impregnated polymer insulating cable. However, a fraction of the carriers can be trapped at levels deep enough to retain them when the field is inverted. The amount of charge in AC should increase slower than in direct current, hetero charge means that the polarity of the space charge is opposite to that of neighboring electrode, and homo charge is the reverse situation.
Under high voltage application, a charge near the electrode is expected to reduce the breakdown voltage. After polarity reversal under ac conditions, the charge is converted to hetero space charge. The reflection coefficient can be as low as 0.105 but is usually near 0.5, for Tungsten, A0 =0.6 to 1.0 ×106 A m−2 K−2, and φ =4.52 eV. At 2500 °C, the emission is 28207 A/m2, the emission current as given above is many times greater than that normally collected by the electrodes, except in some pulsed valves such as the cavity magnetron. Most of the emitted by the cathode are driven back to it by the repulsion of the cloud of electrons in its neighborhood. This is called the space charge effect, in the limit of large current densities, J is given by the Child-Langmuir equation below, rather than by the thermionic emission equation above. Space charge is an inherent property of all vacuum tubes and this has at times made life harder or easier for electrical engineers who used tubes in their designs.
For example, space charge significantly limited the application of triode amplifiers which led to further innovations such as the vacuum tube tetrode. On the other hand, space charge was useful in some applications because it generates a negative EMF within the tubes envelope. Grid bias could be achieved by using a grid voltage in addition to the control voltage. This could improve the control and fidelity of amplification
Those electrons are in turn accelerated and free additional electrons. The result is a multiplication that permits electrical conduction through the gas. The discharge requires a source of electrons and a significant electric field. The Townsend discharge is named after John Sealy Townsend, who discovered the fundamental ionisation mechanism by his work between 1897 and 1901, the avalanche occurs in a gaseous medium that can be ionised. The electric field and the mean path of the electron must allow free electrons to acquire an energy level that can cause impact ionisation. If the electric field is too small, the electrons do not acquire enough energy, if the mean free path is too short, the electron gives up its acquired energy in a series of non-ionising collisions. If the mean free path is too long, the electron reaches the anode before colliding with another molecule, the avalanche mechanism is shown in the accompanying diagram. The electric field is applied across a gaseous medium, initial ions are created with ionising radiation, an original ionisation event produces an ion pair, the positive ion accelerates towards the cathode while the free electron accelerates towards the anode.
If the electric field is strong enough, the electron can gain sufficient velocity to liberate another electron when it next collides with a molecule. The two free electrons travel towards the anode and gain sufficient energy from the field to cause further impact ionisations. This process is effectively a chain reaction that generates free electrons, the total number of electrons reaching the anode is equal to the number of collisions, plus the single initiating free electron. Initially, the number of collisions grows exponentially, the limit to the multiplication in an electron avalanche is known as the Raether limit. The Townsend avalanche can have a range of current densities. In common gas-filled tubes, such as used as gaseous ionisation detectors. Townsends early experimental apparatus consisted of parallel plates forming two sides of a chamber filled with a gas. A direct current high-voltage source was connected between the plates, the lower voltage plate being the cathode while the other was the anode, Townsend observed currents varying exponentially over ten or more orders of magnitude with a constant applied voltage when the distance between the plates was varied.
He discovered that gas pressure influenced conduction, he was able to generate ions in gases at low pressure with a lower voltage than that required to generate a spark. This observation overturned conventional thinking about the amount of current that a gas could conduct
Plasma is one of the four fundamental states of matter, the others being solid and gas. Yet unlike these three states of matter, plasma does not naturally exist on the Earth under normal surface conditions, the term was first introduced by chemist Irving Langmuir in the 1920s. However, true plasma production is from the separation of these ions and electrons that produces an electric field. Based on the environmental temperature and density either partially ionised or fully ionised forms of plasma may be produced. The positive charge in ions is achieved by stripping away electrons from atomic nuclei, the number of electrons removed is related to either the increase in temperature or the local density of other ionised matter. Plasma may be the most abundant form of matter in the universe, although this is currently tentative based on the existence. Plasma is mostly associated with the Sun and stars, extending to the rarefied intracluster medium, Plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879.
The nature of the Crookes tube cathode ray matter was identified by British physicist Sir J. J. The term plasma was coined by Irving Langmuir in 1928, perhaps because the glowing discharge molds itself to the shape of the Crookes tube and we shall use the name plasma to describe this region containing balanced charges of ions and electrons. Plasma is a neutral medium of unbound positive and negative particles. Although these particles are unbound, they are not ‘free’ in the sense of not experiencing forces, in turn this governs collective behavior with many degrees of variation. The average number of particles in the Debye sphere is given by the plasma parameter, bulk interactions, The Debye screening length is short compared to the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, when this criterion is satisfied, the plasma is quasineutral. Plasma frequency, The electron plasma frequency is compared to the electron-neutral collision frequency.
When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics, for plasma to exist, ionization is necessary. The term plasma density by itself refers to the electron density, that is. The degree of ionization of a plasma is the proportion of atoms that have lost or gained electrons, even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma. The degree of ionization, α, is defined as α = n i n i + n n, where n i is the number density of ions and n n is the number density of neutral atoms
Electrical breakdown or dielectric breakdown is a long reduction in the resistance of an electrical insulator when the voltage applied across it exceeds the breakdown voltage. This results in the insulator becoming electrically conductive, electrical breakdown may be a momentary event, or may lead to a discontinuous arc charge if protective devices fail to interrupt the current in a low power circuit. Under sufficient electrical stress, electrical breakdown can occur within solids, however, the specific breakdown mechanisms are significantly different for each, particularly in different kinds of dielectric medium. Electrical breakdown can occur across the insulators that suspend overhead power lines, within underground power cables. Breakdown mechanisms seem to differ in solids and gasses, breakdown is influenced by electrode material, sharp curvature of conductor material, the size of the gap between the electrodes, and the density of the material in the gap. In solid materials a long-time partial discharge typically precedes breakdown, degrading the insulators, ultimately the partial discharge chars through a channel of carbonized material that conducts current across the gap.
There are several mechanisms for breakdown in liquids, small impurities. In liquefied gases used as coolants for superconductivity – such as Helium at 4.2 K or Nitrogen at 96 K – bubbles should induce breakdown, in oil-cooled and oil-insulated transformers the field strength for breakdown is about 20 kV/mm. Despite the purified oils used, small particle contaminants are blamed, thermal effects are proposed for gases by some authors, since breakdown in 50/60 Hz AC lines sometimes occurs long after the maximum voltage is reached. Electrical breakdown occurs within a gas when the strength of the gas is exceeded. Regions of intense voltage gradients can cause gas to partially ionize. This is done deliberately in low pressure such as in fluorescent lights or in an electrostatic precipitator. The voltage that leads to electrical breakdown of a gas is approximated by Paschens Law, partial electrical breakdown of the air causes the fresh air smell of ozone during thunderstorms or around high-voltage equipment.
Although air is normally an excellent insulator, when stressed by a high voltage, air can begin to break down. Across relatively small gaps, breakdown voltage in air is a function of gap length times pressure, if the voltage is sufficiently high, complete electrical breakdown of the air will culminate in an electrical spark or an electric arc that bridges the entire gap. The color of the spark depends upon the gases that make up the gaseous media, while the small sparks generated by static electricity may barely be audible, larger sparks are often accompanied by a loud snap or bang. Lightning is an example of a spark that can be many miles long. If a fuse or circuit breaker fails to interrupt the current through a spark in a circuit, current may continue
A streamer discharge, known as filamentary discharge, is a type of transient electrical discharge. Streamer discharges can form when a medium is exposed to a large potential difference. These electron avalanches create ionized, electrically conductive regions in the air near the electrode creating the electric field, the space charge created by the electron avalanches gives rise to an additional electric field. This field can enhance the growth of new avalanches in a particular direction, the ionized region grows quickly in that direction, forming a finger-like discharge called a streamer. Streamers are transient and filamentary, which makes them different from corona discharges and they are used in applications such as ozone production, air purification or plasma medicine. Streamers pave the way for arcs and lightning leaders, in which the paths created by streamers are heated by large currents. Streamers can be observed as sprites in the upper atmosphere, due to the low pressure, sprites are much larger than streamers at ground pressure, see the similarity laws below.
The theory of streamer discharges was preceded by John Sealy Townsends discharge theory from around 1900, however, it became clear that this theory was sometimes inconsistent with observations. This was especially true for discharges that were longer or at higher pressure, in 1939, Loeb and Raether independently described a new type of discharge, based on their experimental observations. Shortly thereafter, in 1940, Meek presented the theory of spark discharge and this new theory of streamer discharges successfully explained the experimental observations. Streamers are used in such as ozone generation, air purification. An important property is that the plasma they generate is strongly non-equilibrium, chemical reactions can be triggered in a gas without heating it. This is important for plasma medicine, where bullets, or guided streamers, can be used for wound treatment. Streamers can emerge when an electric field is applied to an insulating material. Streamers can only form in areas where the field exceeds the dielectric strength of the medium.
For air at atmospheric pressure, this is roughly 30 kV per centimeter, the electric field accelerates the few electrons and ions that are always present in air, due to natural processes such as cosmic rays, radioactive decay, or photoionization. Ions are much heavier, so they move very slowly compared to electrons, as the electrons move through the medium, they collide with the neutral molecules or atoms. Important collisions are, Elastic collisions, which change the direction of motion of the electrons, where the neutral particle is excited, and the electron loses the corresponding energy
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the voltage difference between the conductors exceeds the voltage of the gas within the gap, a spark forms, ionizing the gas. An electric current flows until the path of ionized gas is broken or the current reduces below a value called the holding current. This usually happens when the drops, but in some cases occurs when the heated gas rises, stretching out. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound, Spark gaps were used historically in early electrical equipment, such as spark gap radio transmitters, electrostatic machines, and X-ray machines. The light emitted by a spark does not come from the current of electrons itself, when electrons collide with molecules of air in the gap, they excite their orbital electrons to higher energy levels. When these excited electrons fall back to their energy levels.
It is impossible for a spark to form in a vacuum. Without intervening matter capable of electromagnetic transitions, the spark will be invisible, Spark gaps are essential to the functioning of a number of electronic devices. A spark plug uses a gap to initiate combustion. The heat of the trail, but more importantly, UV radiation and hot free electrons ignite a fuel-air mixture inside an internal combustion engine, or a burner in a furnace, oven. The more UV radiation is produced and successfully spread into the combustion chamber, Spark gaps are frequently used to prevent voltage surges from damaging equipment. Spark gaps are used in switches, large power transformers, in power plants. Such switches are constructed with a large, remote-operated switching blade with a hinge as one contact, if the blade is opened, a spark may keep the connection between blade and spring conducting. Here, a Jacobs ladder on top of the switch will pull the arc apart, one might find small Jacobs ladders mounted on top of ceramic insulators of high-voltage pylons.
These are sometimes called horn gaps, if a spark should ever manage to jump over the insulator and give rise to an arc, it will be extinguished. Smaller spark gaps are used to protect sensitive electrical or electronic equipment from high-voltage surges. In sophisticated versions of these devices, a spark gap breaks down during an abnormal voltage surge, safely shunting the surge to ground
A flashtube, called a flashlamp, is an electric arc lamp designed to produce extremely intense, full-spectrum white light for very short durations. Flashtubes are made of a length of tubing with electrodes at either end and are filled with a gas that. Flashtubes are used mostly for photographic purposes but are employed in scientific, industrial. The lamp comprises a hermetically sealed tube, which is filled with a noble gas, usually xenon. Additionally, a high power source is necessary to energize the gas as a trigger event. A charged capacitor is used to supply energy for the flash. In some applications, the emission of light is undesired, whether due to production of ozone, damage to laser rods, degradation of plastics. In these cases, a fused silica is used. A better alternative is a cerium-doped quartz, it does not suffer from solarization and has higher efficiency and its cutoff is at about 380 nm. The power level of the lamps is rated in watts/area, total electrical input power divided by the inner wall surface.
Cooling of the electrodes and the envelope is of high importance at high power levels. Air cooling is sufficient for lower power levels. High power lamps are cooled with a liquid, typically by flowing demineralized water through a tube in which the lamp is encased, water-cooled lamps will generally have the glass shrunk around the electrodes, to provide a direct thermal conductor between them and the cooling water. The cooling medium should flow across the length of the lamp. Above 15 W/cm2 forced air cooling is required, liquid cooling if in a confined space, liquid cooling is generally necessary above 30 W/cm2. For this reason, thinner glass is used for continuous-wave arc-lamps. Thicker materials can generally handle more impact energy from the wave that a short-pulsed arc can generate. The material of the envelope provides another limit for the power,1 mm thick fused quartz has a limit of 200 W/cm2
Electrical discharge machining
Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the tool or electrode, while the other is called the workpiece-electrode, the process depends upon the tool and workpiece not making actual contact. This phenomenon is the same as the breakdown of a capacitor, as a result, material is removed from the electrodes. Adding new liquid dielectric in the volume is commonly referred to as flushing. Also, after a current flow, the difference of potential between the electrodes is restored to what it was before the breakdown, so that a new liquid dielectric breakdown can occur, the erosive effect of electrical discharges was first noted in 1770 by English physicist Joseph Priestley. Two Russian scientists, B. R. Butinzky and N. I, were tasked in 1943 to investigate ways of preventing the erosion of tungsten electrical contacts due to sparking.
They failed in this task but found that the erosion was more precisely controlled if the electrodes were immersed in a dielectric fluid and this led them to invent an EDM machine used for working difficult-to-machine materials such as tungsten. The Lazarenkos machine is known as an R-C-type machine, after the circuit used to charge the electrodes. Simultaneously but independently, an American team, Harold Stark, Victor Harding, initially constructing their machines from feeble electric-etching tools, they were not very successful. But more powerful sparking units, combined with automatic spark repetition, Stark and Beavers machines were able to produce 60 sparks per second. Later machines based on their design used vacuum tube circuits that were able to produce thousands of sparks per second, the wire-cut type of machine arose in the 1960s for the purpose of making tools from hardened steel. The tool electrode in wire EDM is simply a wire, to avoid the erosion of material from the wire causing it to break, the wire is wound between two spools so that the active part of the wire is constantly changing.
The earliest numerical controlled machines were conversions of punched-tape vertical milling machines, the first commercially available NC machine built as a wire-cut EDM machine was manufactured in the USSR in 1967. Machines that could optically follow lines on a master drawing were developed by David H. Dulebohns group in the 1960s at Andrew Engineering Company for milling and grinding machines, master drawings were produced by computer numerical controlled plotters for greater accuracy. A wire-cut EDM machine using the CNC drawing plotter and optical line follower techniques was produced in 1974, dulebohn used the same plotter CNC program to directly control the EDM machine, and the first CNC EDM machine was produced in 1976. Electrical discharge machining is a machining method primarily used for hard metals or those that would be difficult to machine with traditional techniques. EDM typically works with materials that are conductive, although methods for machining insulating ceramics with EDM have been proposed. EDM can cut intricate contours or cavities in pre-hardened steel without the need for treatment to soften and re-harden them
Lichtenberg figures, or Lichtenberg dust figures, are branching electric discharges that sometimes appear on the surface or in the interior of insulating materials. Lichtenberg figures are associated with the progressive deterioration of high voltage components. Lichtenberg figures are now known to occur on or within solids, Lichtenberg figures are named after the German physicist Georg Christoph Lichtenberg, who originally discovered and studied them. When they were first discovered, it was thought that their characteristic shapes might help to reveal the nature of positive and negative electric fluids, in 1777, Lichtenberg built a large electrophorus to generate high voltage static electricity through induction. After discharging a high point to the surface of an insulator. By pressing blank sheets of paper onto these patterns, Lichtenberg was able to transfer and record these images and this discovery was the forerunner of the modern day science of plasma physics. Although Lichtenberg only studied two-dimensional figures, modern high voltage researchers study 2D and 3D figures on, Lichtenberg figures are now known to be examples of fractals.
Two-dimensional Lichtenberg figures can be produced by placing a sharp-pointed needle perpendicular to the surface of a plate, such as of resin, ebonite. The point is positioned very near or contacting the plate, a source of high voltage, such as a Leyden jar or a static electricity generator, is applied to the needle, typically through a spark gap. This creates a sudden, small electrical discharge along the surface of the plate and this deposits stranded areas of charge onto the surface of the plate. These electrified areas are tested by sprinkling a mixture of powdered flowers of sulfur, during handling, powdered sulfur tends to acquire a slight negative charge, while red lead tends to acquire a slight positive charge. The negatively electrified sulfur is attracted to the positively electrified areas of the plate, if the charge areas were positive, a widely extending patch is seen on the plate, consisting of a dense nucleus, from which branches radiate in all directions. Negatively charged areas are smaller and have a sharp circular or fan-like boundary entirely devoid of branches.
Heinrich Rudolf Hertz employed Lichtenberg dust figures in his seminal work proving Maxwells electromagnetic wave theories, the difference between positive and negative figures seems to depend on the presence of air, for the difference tends to disappear when the experiment is conducted in vacuum. This electrification would favor the spread of a positive, but hinder that of a negative discharge and it is now known that electrical charges are transferred to the insulators surface through small spark discharges that occur along the boundary between the gas and insulator surface. Once transferred to the insulator, these excess charges become temporarily stranded, the shapes of the resulting charge distributions reflect the shape of the spark discharges which, in turn, depend on the high voltage polarity and pressure of the gas. Using a higher applied voltage will generate larger diameter and more branched figures and it is now known that positive Lichtenberg figures have longer, branching structures because long sparks within air can more easily form and propagate from positively charged high voltage terminals.
This property has been used to measure the transient voltage polarity, another type of 2D Lichtenberg figure can be created when an insulating surface becomes contaminated with semiconducting material
Lightning is a sudden electrostatic discharge that occurs during a thunder storm. This discharge occurs between electrically charged regions of a cloud, between two clouds, or between a cloud and the ground. The charged regions in the atmosphere temporarily equalize themselves through this discharge referred to as an if it hits an object on the ground. Lightning causes light in the form of plasma, and sound in the form of thunder, Lightning may be seen and not heard when it occurs at a distance too great for the sound to carry as far as the light from the strike or flash. This article incorporates public domain material from the National Oceanic and Atmospheric Administration document Understanding Lightning, the details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. The main charging area in a thunderstorm occurs in the part of the storm where air is moving upward rapidly and temperatures range from -15 to -25 Celsius.
At that place, the combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets, small ice crystals, the updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is larger and denser. The differences in the movement of the precipitation cause collisions to occur, when the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud, the larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward the lower part of the storm. The result is that the part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. This part of the cloud is called the anvil. While this is the charging process for the thunderstorm cloud.
In addition, there is a small but important positive charge buildup near the bottom of the cloud due to the precipitation. Many factors affect the frequency, distribution and physical properties of a lightning flash in a particular region of the world. These factors include ground elevation, prevailing wind currents, relative humidity, proximity to warm and cold bodies of water, to a certain degree, the ratio between IC, CC and CG lightning may vary by season in middle latitudes. Lightnings relative unpredictability limits a complete explanation of how or why it occurs, the actual discharge is the final stage of a very complex process. At its peak, a thunderstorm produces three or more strikes to the Earth per minute