A Tesla coil is an electrical resonant transformer circuit designed by inventor Nikola Tesla in 1891. It is used to produce low-current, high frequency alternating-current electricity. Tesla experimented with a number of different configurations consisting of two, or sometimes three, coupled resonant electric circuits. Tesla used these circuits to conduct innovative experiments in electrical lighting, phosphorescence, X-ray generation, high frequency alternating current phenomena and the transmission of electrical energy without wires. Tesla coil circuits were used commercially in sparkgap radio transmitters for wireless telegraphy until the 1920s, in medical equipment such as electrotherapy and violet ray devices. Today, their main usage is for entertainment and educational displays, although small coils are still used as leak detectors for high vacuum systems. A Tesla coil is a radio frequency oscillator that drives an air-core double-tuned resonant transformer to produce high voltages at low currents.
Tesla's original circuits as well as most modern coils use a simple spark gap to excite oscillations in the tuned transformer. More sophisticated designs use transistor or thyristor switches or vacuum tube electronic oscillators to drive the resonant transformer. Tesla coils can produce output voltages from 50 kilovolts to several million volts for large coils; the alternating current output is in the low radio frequency range between 50 kHz and 1 MHz. Although some oscillator-driven coils generate a continuous alternating current, most Tesla coils have a pulsed output; the common spark-excited Tesla coil circuit, shown below, consists of these components: A high voltage supply transformer, to step the AC mains voltage up to a high enough voltage to jump the spark gap. Typical voltages are between 30 kilovolts. A capacitor that forms a tuned circuit with the primary winding L1 of the Tesla transformer A spark gap that acts as a switch in the primary circuit The Tesla coil, an air-core double-tuned resonant transformer, which generates the high output voltage.
Optionally, a capacitive electrode in the form of a smooth metal sphere or torus attached to the secondary terminal of the coil. Its large surface area suppresses premature air breakdown and arc discharges, increasing the Q factor and output voltage; the specialized transformer used in the Tesla coil circuit, called a resonant transformer, oscillation transformer or radio-frequency transformer, functions differently from an ordinary transformer used in AC power circuits. While an ordinary transformer is designed to transfer energy efficiently from primary to secondary winding, the resonant transformer is designed to temporarily store electrical energy; each winding has a capacitance across it and functions as an LC circuit, storing oscillating electrical energy, analogously to a tuning fork. The primary coil consisting of a few turns of heavy copper wire or tubing, is connected to a capacitor through the spark gap; the secondary coil consists of many turns of fine wire on a hollow cylindrical form inside the primary.
The secondary is not connected to an actual capacitor, but it functions as an LC circuit, the inductance of resonates with stray capacitance, the sum of the stray parasitic capacitance between the windings of the coil, the capacitance of the toroidal metal electrode attached to the high voltage terminal. The primary and secondary circuits are tuned so they resonate at the same frequency, they have the same resonant frequency; this allows them to exchange energy, so the oscillating current alternates back and forth between the primary and secondary coils. The peculiar design of the coil is dictated by the need to achieve low resistive energy losses at high frequencies, which results in the largest secondary voltages: Ordinary power transformers have an iron core to increase the magnetic coupling between the coils; however at high frequencies an iron core causes energy losses due to eddy currents and hysteresis, so it is not used in the Tesla coil. Ordinary transformers are designed to be "tightly coupled".
Due to the iron core and close proximity of the windings, they have a high mutual inductance, the coupling coefficient is close to unity 0.95 - 1.0, which means all the magnetic field of the primary winding passes through the secondary. The Tesla transformer in contrast is "loosely coupled", the primary winding is larger in diameter and spaced apart from the secondary, so the mutual inductance is lower and the coupling coefficient is only 0.05 to 0.2. This means that only 5% to 20% of the magnetic field of the primary coil passes through the secondary when it is open circuited; the loose coupling slows the exchange of energy between the primary and secondary coils, which allows the oscillating energy to stay in the secondary circuit longer before it returns to the primary and begins dissipating in the spark. Each winding is limited to a single layer of wire, which reduces proximity effect losses; the primary carries high currents. Since high frequency current flows on the surface of conductors due to skin effect, it is made of copper tubing or strip with a large surface area to reduce resistance, its turns are spaced apart, which reduces proximity effect losses and arcing between turns.
The output circuit can have two forms: Unipolar - One end of the secondary winding is connected to a single high voltage terminal, the other end is grounded. This type is used in modern coils designed for entertainment; the primary winding is located near the bottom, low potential en
In electronics, a vacuum tube, an electron tube, or valve or, colloquially, a tube, is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons from a heated cathode and is used for a number of fundamental electronic functions such as signal amplification and current rectification. Non-thermionic types, such as a vacuum phototube however, achieve electron emission through the photoelectric effect, are used for such as the detection of light levels. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube; the simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Current can only flow in one direction through the device—from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grid or grids.
These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to the development of radio, radar, sound recording and reproduction, long distance telephone networks, analogue and early digital computers. Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, created the discipline of electronics. In the 1940s the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient and durable, cheaper than thermionic tubes. From the mid-1960s, thermionic tubes were being replaced with the transistor. However, the cathode-ray tube remained the basis for television monitors and oscilloscopes until the early 21st century. Thermionic tubes still have some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers, amplifiers that audio enthusiasts prefer for their tube sound.
Not all electronic circuit valves/electron tubes are vacuum tubes. Gas-filled tubes are similar devices, but containing a gas at low pressure, which exploit phenomena related to electric discharge in gases without a heater. One classification of thermionic vacuum tubes is by the number of active electrodes. A device with two active elements is a diode used for rectification. Devices with three elements are triodes used for switching. Additional electrodes create tetrodes, so forth, which have multiple additional functions made possible by the additional controllable electrodes. Other classifications are: by frequency range by power rating by cathode/filament type and Warm-up time by characteristic curves design by application specialized parameters specialized functions tubes used to display information Tubes have different functions, such as cathode ray tubes which create a beam of electrons for display purposes in addition to more specialized functions such as electron microscopy and electron beam lithography.
X-ray tubes are vacuum tubes. Phototubes and photomultipliers rely on electron flow through a vacuum, though in those cases electron emission from the cathode depends on energy from photons rather than thermionic emission. Since these sorts of "vacuum tubes" have functions other than electronic amplification and rectification they are described in their own articles. A vacuum tube consists of two or more electrodes in a vacuum inside an airtight envelope. Most tubes have glass envelopes with a glass-to-metal seal based on kovar sealable borosilicate glasses, though ceramic and metal envelopes have been used; the electrodes are attached to leads. Most vacuum tubes have a limited lifetime, due to the filament or heater burning out or other failure modes, so they are made as replaceable units. Tubes were a frequent cause of failure in electronic equipment, consumers were expected to be able to replace tubes themselves. In addition to the base terminals, some tubes had an electrode terminating at a top cap.
The principal reason for doing this was to avoid leakage resistance through the tube base for the high impedance grid input. The bases were made with phenolic insulation which performs poorly as an insulator in humid conditions. Other reasons for using a top cap include improving stability by reducing grid-to-anode capacitance, improved high-frequency performance, keeping a high plate voltage away from lower voltages, accommodating one more electrode than allowed by the base. There was an occasional design that had two top cap connections; the earliest vacuum tubes evolved from incandescent light bulbs, containing a filament sealed in an evacuated glass envelope. When hot, the filament releases electrons into the vacuum, a process called thermio
Frequency is the number of occurrences of a repeating event per unit of time. It is referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency; the period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example: if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals, radio waves, light. For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics and radio, frequency is denoted by a Latin letter f or by the Greek letter ν or ν; the relation between the frequency and the period T of a repeating event or oscillation is given by f = 1 T.
The SI derived unit of frequency is the hertz, named after the German physicist Heinrich Hertz. One hertz means. If a TV has a refresh rate of 1 hertz the TV's screen will change its picture once a second. A previous name for this unit was cycles per second; the SI unit for period is the second. A traditional unit of measure used with rotating mechanical devices is revolutions per minute, abbreviated r/min or rpm. 60 rpm equals one hertz. As a matter of convenience and slower waves, such as ocean surface waves, tend to be described by wave period rather than frequency. Short and fast waves, like audio and radio, are described by their frequency instead of period; these used conversions are listed below: Angular frequency denoted by the Greek letter ω, is defined as the rate of change of angular displacement, θ, or the rate of change of the phase of a sinusoidal waveform, or as the rate of change of the argument to the sine function: y = sin = sin = sin d θ d t = ω = 2 π f Angular frequency is measured in radians per second but, for discrete-time signals, can be expressed as radians per sampling interval, a dimensionless quantity.
Angular frequency is larger than regular frequency by a factor of 2π. Spatial frequency is analogous to temporal frequency, but the time axis is replaced by one or more spatial displacement axes. E.g.: y = sin = sin d θ d x = k Wavenumber, k, is the spatial frequency analogue of angular temporal frequency and is measured in radians per meter. In the case of more than one spatial dimension, wavenumber is a vector quantity. For periodic waves in nondispersive media, frequency has an inverse relationship to the wavelength, λ. In dispersive media, the frequency f of a sinusoidal wave is equal to the phase velocity v of the wave divided by the wavelength λ of the wave: f = v λ. In the special case of electromagnetic waves moving through a vacuum v = c, where c is the speed of light in a vacuum, this expression becomes: f = c λ; when waves from a monochrome source travel from one medium to another, their frequency remains the same—only their wavelength and speed change. Measurement of frequency can done in the following ways, Calculating the frequency of a repeating event is accomplished by counting the number of times that event occurs within a specific time period dividing the count by the length of the time period.
For example, if 71 events occur within 15 seconds the frequency is: f = 71 15 s ≈ 4.73 Hz If the number of counts is not large, it is more accurate to measure the time interval for a predetermined number of occurrences, rather than the number of occurrences within a specified time. The latter method introduces a random error into the count of between zero and one count, so on average half a count; this is called gating error and causes an average error in the calculated frequency of Δ f = 1 2 T
An Oudin coil called an Oudin oscillator or Oudin resonator, is a resonant transformer circuit that generates high voltage, high frequency alternating current electricity at low current levels, used in the obsolete medical field of electrotherapy around the turn of the 20th century. It is similar to a Tesla coil, with the difference being that the Oudin coil was connected as an autotransformer, it was invented in 1893 by French physician Paul Marie Oudin as a modification of physician Jacques Arsene d'Arsonval's electrotherapy equipment and used in quack medicine until 1930. The high voltage output terminal of the coil was connected to an insulated handheld electrode which produced luminous brush discharges, which were applied to the patient's body to treat various medical conditions in electrotherapy. Oudin and Tesla coils are spark-excited air-core double-tuned transformer circuits that use resonance to generate high voltages at low currents, they produce alternating current in the radio frequency range.
The medical coils of the early 20th century produced potentials of 50,000 to nearly a million volts, at frequencies in the range 200 kHz to 5 MHz. The primary circuit of the coil has Leyden jar capacitors which in combination with the primary winding of the coil make a resonant circuit. In medical coils two capacitors were used for safety, one in each side of the primary circuit, to isolate the patient from the lethal low frequency primary current; the primary circuit has a spark gap that acts as a switch to excite oscillations in the primary. The primary circuit is powered by a high voltage transformer or induction coil at a potential of 2 - 15 kV; the transformer charges the capacitors, which discharge through the spark gap and the primary winding. This cycle is repeated many times per second. During each spark, the charge moves back and forth between the capacitor plates through the primary coil, creating a damped RF oscillating current in the primary tuned circuit which induced the high voltage in the secondary.
The secondary winding is open-circuited, connected to the output electrode of the device. In the Oudin coil, one side of the primary winding is grounded and the other side is connected to the secondary, so the primary and secondary are in series. There were two versions of the Oudin coil: In earlier Oudin circuits the two coils were separate, not magnetically coupled, with a small horizontal primary "D'Arsonval" coil of 20-40 turns with a tap connected to a large vertical secondary "Oudin resonator" with many turns of fine wire, connected to the high voltage terminal on top. In this circuit the high voltage was generated by resonance in the high Q secondary coil; the addition of the "resonator" coil to the "D'Arsonval" coil was Oudin's contribution. In Oudin circuits the coils were magnetically coupled, forming an autotransformer, so the primary induces an EMF in the secondary by electromagnetic induction. Both coils were wound on the same coil form, the primary consisting of few turns of heavy wire at the bottom with an adjustable tap, connected to the secondary winding, made of many turns of fine wire.
Oudin found. Although it doesn't include a capacitor, the secondary winding is a resonant circuit; when it is excited at this frequency by the primary, large oscillating voltages are induced in the secondary. The number of turns in the primary winding, thus the resonant frequency of the primary, could be adjusted with a tap on the coil; when the two tuned circuits are adjusted to resonate at the same frequency, the large turns ratio of the coil, aided by the high Q of the tuned circuits, steps up the primary voltage to hundreds of thousands to millions of volts at the secondary. The secondary is directly connected to the primary circuit, which carries lethal low frequency 50/60 Hz currents at thousands of volts from the power transformer. Since the Oudin coil was a medical device, with the secondary current applied directly to a person's body, for safety the Oudin circuit has two capacitors, one in each leg of the primary, to isolate the coil and output electrode from the supply transformer at the mains frequency.
Because two identical capacitors in series have half the capacitance of a single capacitor, the resonant frequency of the Oudin circuit is f = 1 2 π L 1 C / 2 The high voltage terminal of the coil was attached through a wire to various types of handheld electrode which the physician used to apply the high voltage to the patient's body. The treatment was not painful for the patient, because alternating current in the radio frequency range, above 10 kHz in frequency, does not cause the sensation of electric shock; the Oudin coil was a "unipolar" generator, with the lower end of the coil grounded, so sometimes only one electrode was applied to the patient and the return path for the currents was through the ground. However a ground wire from the bottom of the coil was used. A drawback of the Oudin coil was that movement of the electrode and wire during use changed th
Therapeutic ultrasound refers to any type of ultrasonic procedure that uses ultrasound for therapeutic benefit. This includes HIFU, targeted ultrasound drug delivery, trans-dermal ultrasound drug delivery, ultrasound hemostasis, cancer therapy, ultrasound assisted thrombolysis It may use focused ultrasound or unfocused ultrasound. Ultrasound is a method of stimulating the tissue beneath the skin's surface using high frequency sound waves, between 800,000 Hz and 2,000,000 Hz, which cannot be heard by humans. There is little evidence that active ultrasound is more effective than placebo treatment for treating patients with pain or a range of musculoskeletal injuries, or for promoting soft tissue healing. High power ultrasound can break up stony deposits or tissue, accelerate the effect of drugs in a targeted area, assist in the measurement of the elastic properties of tissue, can be used to sort cells or small particles for research. Focused high-energy ultrasound pulses can be used to break calculi such as kidney stones and gallstones into fragments small enough to be passed from the body without undue difficulty, a process known as lithotripsy.
Cleaning teeth in dental hygiene. Focused ultrasound sources may be used for cataract treatment by phacoemulsification. Ultrasound can ablate other tissue non-invasively; this is accomplished using a technique known as High Intensity Focused Ultrasound called focused ultrasound surgery. This procedure uses lower frequencies than medical diagnostic ultrasound, but higher time-averaged intensities; the treatment is guided by Magnetic Resonance Imaging. Delivering chemotherapy to brain cancer cells and various drugs to other tissues is called acoustic targeted drug delivery; these procedures use high frequency ultrasound and a range of intensities. The acoustic energy is focused on the tissue of interest to agitate its matrix and make it more permeable for therapeutic drugs. Ultrasound has been used to trigger the release of anti-cancer drugs from delivery vectors including liposomes, polymeric microspheres and self-assembled polymeric. Ultrasound is essential to the procedures of ultrasound-guided sclerotherapy and endovenous laser treatment for the non-surgical treatment of varicose veins.
Ultrasound-assisted lipectomy is Liposuction assisted by ultrasound. There are three potential effects of ultrasound; the first is the increase in blood flow in the treated area. The second is the decrease in pain from the reduction of swelling and edema; the third is the gentle massage of muscle tendons and/ or ligaments in the treated area because no strain is added and any scar tissue is softened. These three benefits are achieved by two main effects of therapeutic ultrasound; the two types of effects are: non thermal effects. Thermal effects are due to the absorption of the sound waves. Non thermal effects are from cavitation and acoustic streaming. Cavitational effects result from the vibration of the tissue causing microscopic bubbles to form, which transmit the vibrations in a way that directly stimulates cell membranes; this physical stimulation appears to enhance the cell-repair effects of the inflammatory response. The first large scale application of ultrasound was around World War II.
Sonar systems were being used to navigate submarines. It was realized that the high intensity ultrasound waves that they were using were heating and killing fish; this led to research in tissue healing effects. Since the 1940s, ultrasound has been used by physical and occupational therapists for therapeutic effects. Ultrasound is applied using a transducer or applicator, in direct contact with the patient's skin. Gel is used on all surfaces of the head to reduce friction and assist transmission of the ultrasonic waves. Therapeutic ultrasound in physical therapy is alternating compression and rarefaction of sound waves with a frequency of 0.7 to 3.3 MHz. Maximum energy absorption in soft tissue occurs from 2 to 5 cm. Intensity decreases, they are absorbed by connective tissue: ligaments and fascia. Conditions for which ultrasound may be used for treatment include the following examples: ligament sprains, muscle strains, joint inflammation, plantar fasciitis, facet irritation, impingement syndrome, rheumatoid arthritis and scar tissue adhesion.
Acoustic tweezers is an emerging tool for contactless separation and manipulation of microparticles and biological cells, using ultrasound in the low MHz range to form standing waves. This is based on the acoustic radiation force which causes particles to be attracted to either the nodes or anti-nodes of the standing wave depending on the acoustic contrast factor, a function of the sound velocities and densities of the particle and of the medium in which the particle is immersed. Application of focused ultrasound in conjunction with microbubbles has been shown to enable non-invasive delivery of epirubicin across the blood–brain barrier in mouse models. Using ultrasound to generate cellular effects in soft tissue has fallen out of favor as research has shown a lack of efficacy and a lack of scientific basis for proposed biophysical effects. According to a 2017 meta-analysis and associated practice guideline, Low intensity pulsed ultrasound should no longer been used for bone regeneration because high quality clinical studies failed to demonstrate a clinical benefit.
An additional effect of low-intensity ultrasound could be its potential to disrupt the b
Dielectric heating known as electronic heating, radio frequency heating, high-frequency heating, is the process in which a radio frequency alternating electric field, or radio wave or microwave electromagnetic radiation heats a dielectric material. At higher frequencies, this heating is caused by molecular dipole rotation within the dielectric. RF dielectric heating at intermediate frequencies, due to its greater penetration over microwave heating, shows greater promise than microwave systems as a method of rapidly heating and uniformly preparing certain food items, killing parasites and pests in certain harvested crops. Molecular rotation occurs in materials containing polar molecules having an electrical dipole moment, with the consequence that they will align themselves in an electromagnetic field. If the field is oscillating, as it is in an electromagnetic wave or in a oscillating electric field, these molecules rotate continuously by aligning with it; this is called dipolar polarisation.
As the field alternates, the molecules reverse direction. Rotating molecules push and collide with other molecules, distributing the energy to adjacent molecules and atoms in the material; the process of energy transfer from the source to the sample is a form of radiative heating. Temperature is related to the average kinetic energy of the atoms or molecules in a material, so agitating the molecules in this way increases the temperature of the material. Thus, dipole rotation is a mechanism by which energy in the form of electromagnetic radiation can raise the temperature of an object. There are many other mechanisms by which this conversion occurs. Dipole rotation is the mechanism referred to as dielectric heating, is most observable in the microwave oven where it operates most efficaciously on liquid water, but much less so, on fats and sugars; this is because fats and sugar molecules are far less polar than water molecules, thus less affected by the forces generated by the alternating electromagnetic fields.
Outside of cooking, the effect can be used to heat solids, liquids, or gases, provided they contain some electric dipoles. Dielectric heating involves the heating of electrically insulating materials by dielectric loss. A changing electric field across the material causes energy to be dissipated as the molecules attempt to line up with the continuously changing electric field; this changing electric field may be caused by an electromagnetic wave propagating in free space, or it may be caused by a alternating electric field inside a capacitor. In the latter case, there is no freely-propagating electromagnetic wave, the changing electric field may be seen as analogous to the electric component of an antenna near field. In this case, although the heating is accomplished by changing the electric field inside the capacitive cavity at radio-frequency frequencies, no actual radio waves are either generated or absorbed. In this sense, the effect is the direct electrical analog of magnetic induction heating, near-field effect.
Frequencies in the range of 10–100 MHz are necessary to cause dielectric heating, although higher frequencies work well or better, in some materials lower frequencies have significant heating effects due to more unusual mechanisms. For example, in conductive liquids such as salt water, ion-drag causes heating, as charged ions are "dragged" more back and forth in the liquid under influence of the electric field, striking liquid molecules in the process and transferring kinetic energy to them, translated into molecular vibrations and thus into thermal energy. Dielectric heating at low frequencies, as a near-field effect, requires a distance from electromagnetic radiator to absorber of less than 1/2π ≈ 1/6 of a wavelength, it is thus a contact process or near-contact process, since it sandwiches the material to be heated between metal plates taking the place of the dielectric in what is a large capacitor. However, actual electrical contact is not necessary for heating a dielectric inside a capacitor, as the electric fields that form inside a capacitor subjected to a voltage do not require electrical contact of the capacitor plates with the dielectric material between the plates.
Because lower frequency electrical fields penetrate non-conductive materials far more than do microwaves, heating pockets of water and organisms deep inside dry materials like wood, it can be used to heat and prepare many non-electrically conducting food and agricultural items, so long as they fit between the capacitor plates. At high frequencies, the wavelength of the electromagnetic field becomes shorter than the distance between the metal walls of the heating cavity, or than the dimensions of the walls themselves; this is the case inside a microwave oven. In such cases, conventional far-field electromagnetic waves form, are absorbed to cause heating, but the dipole-rotation mechanism of heat deposition remains the same. However, microwaves are not efficient at causing the heating effects of low frequency fields that depend on slower molecular motion, such as those caused by ion-drag. Dielectric heating must be distinguished from Joule heating of conductive media, caused by induced electric currents in the media.
For dielectric heating, the generated power density per volume is given by: Q = ω ⋅ ε r ″ ⋅ ε 0 ⋅ E
Cauterization is a medical practice or technique of burning a part of a body to remove or close off a part of it. It destroys some tissue in an attempt to mitigate bleeding and damage, remove an undesired growth, or minimize other potential medical harm, such as infections when antibiotics are unavailable; the practice was once widespread for treatment of wounds. Its utility before the advent of antibiotics was said to be effective at more than one level: To prevent exsanguination To close amputationsCautery was believed to prevent infection, but current research shows that cautery increases the risk for infection by causing more tissue damage and providing a more hospitable environment for bacterial growth. Actual cautery refers to the metal device heated to a dull red glow, that a physician applies to produce blisters, to stop bleeding of a blood vessel, for other similar purposes; the main forms of cauterization used today in the first world are electrocautery and chemical cautery—both are, for example, prevalent in the removal of unsightly warts and stopping nosebleeds.
Cautery can mean the branding of a human, either recreational or forced. Cauterize is a Middle English word borrowed from the Old French cauteriser, from Late Latin cauterizare "to burn or brand with a hot iron", from Greek καυτηριάζειν > kauteriazein, from καυτήρ, kauter, "burning or branding iron", καίειν, "to burn". Cauterization has been used to stop heavy bleeding since antiquity; the process was described in the Edwin Smith Papyrus and Hippocratic Corpus. It was used to control hemorrhages those resulting from surgery, in ancient Greece. Archigenes recommended cauterization in the event of hemorrhaging wounds, Leonides of Alexandria described excising breast tumors and cauterizing the resulting wound in order to control bleeding; the Chinese Su wen recommends cauterization as a treatment for various ailments, including dog bites. Indigenous peoples of the Americas, ancient Arabs, Persians used the technique. Tools used in the ancient cauterization process ranged from heated lances to cauterizing knives.
The piece of metal was applied to the wound. This caused tissues and blood to heat to extreme temperatures, causing coagulation of the blood and thus controlling the bleeding, at the cost of extensive tissue damage. In rarer cases, cauterization was instead accomplished via the application of cauterizing chemicals like lye. Cauterization continued to be used as a common treatment in medieval times. While employed to stop blood loss, it was used in cases of tooth extraction and as a treatment for mental illness. In the Arab world, scholars Al-Zahrawi and Avicenna wrote about techniques and instruments used for cauterization; the technique of ligature of the arteries as an alternative to cauterization was improved and used more by Ambroise Paré. Electrocauterization is the process of destroying tissue using heat conduction from a metal probe heated by electric current; the procedure stops bleeding from small vessels. Electrocautery applies high frequency alternating current by a bipolar method, it can be a continuous waveform to cut tissue, or intermittent to coagulate tissue.
The electrically produced heat in this process inherently can do numerous things to the tissue, depending on the waveform and power level, including cauterize, coagulate and dry. Thus electrocautery, electrocoagulation, electrodesiccation, electrocurettage are related and can co-occur in the same procedure when desired. Electrodesiccation and curettage is a common procedure. In unipolar cauterization, the physician contacts the tissue with a single small electrode; the circuit's exit point is a large surface area, such as the buttocks. The amount of heat generated depends on the size of contact area, power setting or frequency of current, duration of application, waveform. A constant waveform generates more heat than intermittent; the frequency used in cutting the tissue is higher than in coagulation mode. Bipolar electrocautery passes the current between two tips of a forceps-like tool, it has the advantage of not disturbing other electrical body rhythms and coagulates tissue by pressure. Lateral thermal injury is greater in unipolar than bipolar devices.
Electrocauterization is preferable to chemical cauterization, because chemicals can leach into neighbouring tissue and cauterize outside of intended boundaries. Concern has been raised regarding toxicity of the surgical smoke electrocautery produces; this contains chemicals that, through inhalation, may harm medical staff. Ultrasonic coagulation and ablation systems are available. Many chemical reactions can destroy tissue, some are used in medicine, most to remove small skin lesions such as warts or necrotized tissue, or for hemostasis; because chemicals can leach into areas not intended for cauterization and electrical methods are preferable where practical. Some cauterizing agents are: Silver nitrate is the active ingredient of the lunar caustic, a stick that traditionally looks like a large match, it is pressed onto the lesion for a few moments. Trichloroacetic acid Cantharidin is an extract of the blister beetle that causes epidermal necrosis and blistering, it is used to treat warts. Frequent nosebleeds are most caused by an exposed blood vessel in the nose one in Kiesselbach's plexus.
If the nose is not bleeding at the time, a physician may cauterize it to prevent future bleeding. Cauterization methods include burning the affected area with acid, hot metal, o