Misplaced Pages

#811188

122-650: The Volta River Authority ( VRA ) is the main generator and supplier of electricity in Ghana . They are also responsible for the maintenance of the hydro power supply plant. The VRA was established by the Volta River Development Act, Act 46 of the Republic of Ghana on 26 April 1961. The main purpose of the VRA is to generate and supply electricity for Ghana's needs. It is also responsible for managing

244-455: A conductor 's surface, since otherwise there would be a force along the surface of the conductor that would move the charge carriers to even the potential across the surface. The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre,

366-461: A force on each other, an effect that was known, though not understood, in antiquity. A lightweight ball suspended by a fine thread can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball

488-409: A steady state current, but instead blocks it. The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality

610-415: A body part with electricity that causes a sufficient current to pass through the person's tissues. Contact with energized wiring or devices is the most common cause. In cases of exposure to high voltages , such as on a power transmission tower , direct contact may not be necessary as the voltage may "jump" the air gap to the electrical device. Following an electrical injury from household current, if

732-399: A boundary. The voltage of the shock may have effects ranging from uncomfortable, to painful or even lethal. Most electric fencing is used today for agricultural fencing and other forms of animal control purposes, though it is frequently used to enhance security of restricted areas, and there exist places where lethal voltages are used. Electric shocks are used as a method of torture , since

854-432: A charge of Q coulombs every t seconds passing through an electric potential ( voltage ) difference of V is where Electric power is generally supplied to businesses and homes by the electric power industry . Electricity is usually sold by the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using electricity meters , which keep

976-516: A common reference point to which potentials may be expressed and compared is useful. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground . Earth is assumed to be an infinite source of equal amounts of positive and negative charge and is therefore electrically uncharged—and unchargeable. Electric potential

1098-472: A current of one amp. The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin insulating dielectric layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance . The unit of capacitance

1220-500: A current over time duration curve based classification. These principles are used to determine the risks from capacitors, electric weapons, electric fences and other short pulsed low- and high-voltage electrical applications outside the medical field. Prevention of electrical injuries is one of the fundamental objectives of national electrical codes for permanently-installed electrical systems in buildings. Shock danger may be reduced by use of an extra-low voltage electrical system that

1342-494: A dampened kite string and flown the kite in a storm-threatened sky . A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. He also explained the apparently paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. In 1775, Hugh Williamson reported

SECTION 10

#1732772492812

1464-429: A detailed analysis of the electrical system, and appropriate protection worn if the electrical work must be performed with the electricity on. The minimum current a human can feel depends on the current type ( AC or DC ) as well as frequency for AC. A person can sense electric current as low as 1   mA ( rms ) for 60   Hz AC and as low as 5   mA for DC. At around 10   mA, AC current passing through

1586-448: A few seconds. A domestic power supply voltage (110 or 230 V), 50 or 60 Hz alternating current (AC) through the chest for a duration longer than one second may induce ventricular fibrillation at currents as low as 30 milliamperes (mA). With direct current (DC), 90 to 130 mA are required at the same duration. If the current has a direct pathway to the heart (e.g., via a cardiac catheter or other kind of electrode ),

1708-583: A fixed resistance model. The earliest usage of the term "electrocution" cited by the Oxford English Dictionary was an 1889 newspaper reference to the method of execution then being considered. Shortly thereafter, in 1892, the term was used in Science to refer generically to death or injury caused by electricity. The lethality of an electric shock is dependent on several variables: Other issues affecting lethality are frequency , which

1830-425: A large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh. The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor , the sharp spike of which acts to encourage the lightning strike to develop there, rather than to

1952-402: A millimetre per second, the electric field that drives them itself propagates at close to the speed of light , enabling electrical signals to pass rapidly along wires. Current causes several observable effects, which historically were the means of recognising its presence. That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800,

2074-553: A more reliable source of electrical energy than the electrostatic machines previously used. The recognition of electromagnetism , the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819–1820. Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827. Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell , in particular in his " On Physical Lines of Force " in 1861 and 1862. While

2196-421: A much lower current of less than 1 mA (AC or DC) can cause fibrillation. If not immediately treated by defibrillation , ventricular fibrillation is usually lethal, causing cardiac arrest , because all of the heart muscle fibres move independently instead of in the coordinated action needed for successful cardiac cycle to pump blood and maintain circulation. Short single DC pulses induce VF dependent on

2318-671: A person died from electrocution between July 2000 and October 2011. In Sweden, Denmark, Finland and Norway the number of electric deaths per million inhabitants was 0.6, 0.3, 0.3 and 0.2, respectively, in the years 2007–2011. In Nigeria, analysis of Nigerian Electricity Regulatory Commission data found 126 recorded electrocution deaths and 68 serious injuries in 2020 and the first half of 2021. Most electrocutions are accidental and caused by faulty equipment or poor adherence to regulations. Some distribution companies in Nigeria have higher death rates than others; in 2017, there were 26 deaths on

2440-402: A person has no symptoms, no underlying heart problems, and is not pregnant further testing is not required. Otherwise an electrocardiogram , blood work to check the heart, and urine testing for signs of muscle breakdown may be performed. Management may involve resuscitation , pain medications, wound management, and heart rhythm monitoring . Electrical injuries affect more than 30,000 people

2562-425: A positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current . The motion of negatively charged electrons around an electric circuit , one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of

SECTION 20

#1732772492812

2684-891: A practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work. An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task. The components in an electric circuit can take many forms, which can include elements such as resistors , capacitors , switches , transformers and electronics . Electronic circuits contain active components , usually semiconductors , and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear : while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli. The resistor

2806-646: A prison complex maintained by Dirección de Inteligencia Nacional , a part of the Pinochet regime. In the 1970s, during the Dirty War , the parrilla was used in Argentina. Francisco Tenório Júnior (known as Tenorinho), a Brazilian piano player, was subjected to the parrilla during the military dictatorship in Brazil . The Islamic State has used electric shocks to torture and kill captives. Advocates for

2928-406: A process now known as electrolysis . Their work was greatly expanded upon by Michael Faraday in 1833. Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840. One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in

3050-471: A rapidly changing one. Electric power is the rate at which electric energy is transferred by an electric circuit . The SI unit of power is the watt , one joule per second . Electric power, like mechanical power , is the rate of doing work , measured in watts , and represented by the letter P . The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of

3172-489: A resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm , the unit of resistance, was named in honour of Georg Ohm , and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to

3294-465: A result of electrical injury. Electric shock is also used as a medical therapy, under carefully controlled conditions: Mild electric shocks are also used for entertainment, especially as a practical joke for example in such devices as a shocking pen or a shocking gum . However devices such as a joy buzzer and most other machines in amusement parks today only use vibration that feels somewhat like an electric shock to someone not expecting it. It

3416-595: A running total of the electric energy delivered to a customer. Unlike fossil fuels , electricity is a low entropy form of energy and can be converted into motion or many other forms of energy with high efficiency. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes , transistors , diodes , sensors and integrated circuits , and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes digital switching possible, and electronics

3538-431: A scientific curiosity into an essential tool for modern life. In 1887, Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets, energising electrons. This discovery led to

3660-524: A separate insulation system, distinct from the insulation required for the function of the device, and intended for protection of the user from electrical shock. People and animals can be protected by installing electrical equipment out of reach of passers-by, such as on electrical transmission towers , or by installation in a electrical room only accessible to authorized persons. Stray current leakage or electrical fault current may be diverted by bonding all conductive equipment enclosures together and to

3782-575: A series of experiments to the Royal Society on the shocks delivered by the electric eel ; that same year the surgeon and anatomist John Hunter described the structure of the fish's electric organs . In 1791, Luigi Galvani published his discovery of bioelectromagnetics , demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta 's battery, or voltaic pile , of 1800, made from alternating layers of zinc and copper, provided scientists with

Volta River Authority - Misplaced Pages Continue

3904-515: A series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic , in contrast to minerals such as magnetite , which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating , based on

4026-474: A set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that in a vacuum such a wave would travel at the speed of light , and thus light itself was a form of electromagnetic radiation. Maxwell's equations , which unify light, fields, and charge are one of the great milestones of theoretical physics. Electric shock The injury depends on

4148-477: A solid crystal (such as a germanium crystal) to detect a radio signal by the contact junction effect. In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it. Current flow can be understood in two forms: as negatively charged electrons , and as positively charged electron deficiencies called holes . These charges and holes are understood in terms of quantum physics. The building material

4270-875: A standard ohmmeter do not accurately represent the impedance of human skin over a significant range of conditions. For sinusoidal electrical stimulation less than 10 volts, the skin voltage-current characteristic is quasilinear. Over time, electrical characteristics can become non-linear. The time required varies from seconds to minutes, depending on stimulus, electrode placement, and individual characteristics. Between 10 volts and about 30 volts, skin exhibits non-linear but symmetric electrical characteristics. Above 20 volts, electrical characteristics are both non-linear and symmetric. Skin conductance can increase by several orders of magnitude in milliseconds. This should not be confused with dielectric breakdown , which occurs at hundreds of volts. For these reasons, current flow cannot be accurately calculated by simply applying Ohm's law using

4392-593: A steady current flow (as opposed to a shock from a capacitor or from static electricity ), shocks above 2,700 volts are often fatal, with those above 11,000 volts being usually fatal, though exceptional cases have been noted. According to the Guinness Book of World Records , seventeen-year-old Brian Latasa survived a 230,000 volt shock on the tower of an ultra-high voltage line in Griffith Park , Los Angeles on November 9, 1967. A news report of

4514-511: A wire disturbing the needle of a magnetic compass. He had discovered electromagnetism , a fundamental interaction between electricity and magnetics. The level of electromagnetic emissions generated by electric arcing is high enough to produce electromagnetic interference , which can be detrimental to the workings of adjacent equipment. In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how

4636-448: A wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained. Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction , enabled him to state

4758-402: A wire. The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other. Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope , which although still in use for classroom demonstrations, has been superseded by

4880-447: A worse prognosis . When the path of electric current proceeds through the head, it appears that, with sufficient current applied, loss of consciousness almost always occurs swiftly. This is borne out by some limited self-experimentation by early designers of the electric chair and by research from the field of animal husbandry , where electric stunning has been extensively studied. If ventricular fibrillation occurs (as above),

5002-466: A year in the United States and result in about 1,000 deaths. Heating due to resistance can cause extensive and deep burns . When applied to the hand, electricity can cause involuntary muscle contraction, preventing the victim from untensing their hand muscles and releasing the wire, increasing the risk for serious burns. Voltage levels of 500 to 1000 volts tend to cause internal burns due to

Volta River Authority - Misplaced Pages Continue

5124-584: Is a scalar quantity . That is, it has only magnitude and not direction. It may be viewed as analogous to height : just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field. As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials ) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to

5246-411: Is a vector field . The study of electric fields created by stationary charges is called electrostatics . The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term ' lines of force ' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it

5368-546: Is a conductive energy device (CED), an electroshock gun popularly known by the brand name " Taser ", which fires projectiles that administer the shock through a thin, flexible wire. Although they are illegal for personal use in many jurisdictions, Tasers have been marketed to the general public. Other electroshock weapons such as stun guns, stun batons ("cattle prods"), and electroshock belts administer an electric shock by direct contact. Electric fences are barriers that use electric shocks to deter animals or people from crossing

5490-420: Is absolutely necessary, workers may be trained to use insulated or non-conductive tools, and personal protective equipment such as gloves, face shields, non-conductive boots, or cover-up mats. With proper training and equipment, live-line maintenance is routinely safely carried out on electrical transmission lines energized at hundreds of thousands of volts . There were 550 reported electrocution deaths in

5612-426: Is also used for sexual stimulation . This is usually done via devices that induces erotic electrostimulation . These devices may include a violet wand , transcutaneous electrical nerve stimulation , electrical muscle stimulation , and made-for-play units. Electroshock weapons are incapacitant weapons used for subduing a person by administering electric shock to disrupt superficial muscle functions. One type

5734-413: Is an electric current and produces a magnetic field . In most applications, Coulomb's law determines the force acting on an electric charge. Electric potential is the work done to move an electric charge from one point to another within an electric field, typically measured in volts . Electricity plays a central role in many modern technologies, serving in electric power where electric current

5856-406: Is an especially dangerous source of ventricular fibrillation because it usually exceeds the let-go threshold, while not delivering enough initial energy to propel the person away from the source. However, the potential seriousness of the shock depends on paths through the body that the currents take. If the voltage is less than 200 V, then the human skin, more precisely the stratum corneum ,

5978-452: Is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker. An electric field generally varies in space, and its strength at any one point

6100-467: Is an issue in causing cardiac arrest or muscular spasms. Very high frequency electric current causes tissue burning, but do not stimulate the nerves strongly enough to cause cardiac arrest (see electrosurgery ). Also important is the pathway: if the current passes through the chest or head, there is an increased chance of death. From a main circuit or power distribution panel the damage is more likely to be internal, leading to cardiac arrest . Another factor

6222-401: Is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb , who deduced that charge manifests itself in two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and opposite-charged objects attract . The force acts on

SECTION 50

#1732772492812

6344-473: Is defined as negative, and that by protons is positive. Before these particles were discovered, Benjamin Franklin had defined a positive charge as being the charge acquired by a glass rod when it is rubbed with a silk cloth. A proton by definition carries a charge of exactly 1.602 176 634 × 10  coulombs . This value is also defined as the elementary charge . No object can have a charge smaller than

6466-483: Is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point. The conceptual charge, termed a ' test charge ', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields . As the electric field is defined in terms of force , and force is a vector , having both magnitude and direction , it follows that an electric field

6588-531: Is integral to applications spanning transport , heating , lighting , communications , and computation , making it the foundation of modern industrial society. Long before any knowledge of electricity existed, people were aware of shocks from electric fish . Ancient Egyptian texts dating from 2750 BCE described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek , Roman and Arabic naturalists and physicians . Several ancient writers, such as Pliny

6710-406: Is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere . This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury . A current was allowed through

6832-415: Is most often a crystalline semiconductor . Solid-state electronics came into its own with the emergence of transistor technology. The first working transistor, a germanium -based point-contact transistor , was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947, followed by the bipolar junction transistor in 1948. By modern convention, the charge carried by electrons

6954-443: Is non-linear and depends on many factors such as intensity, duration, history, and frequency of the electrical stimulus. Sweat gland activity, temperature, and individual variation also influence the voltage-current characteristic of skin. In addition to non-linearity, skin impedance exhibits asymmetric and time varying properties. These properties can be modeled with reasonable accuracy. Resistance measurements made at low voltage using

7076-515: Is only of second order importance to fibrillation risk in the case of ultra short contact times with direct currents. But even if the charge itself is harmless, the amount of energy being discharged still can lead to thermal and chemical hazards if its value is high enough. One example of high current electric shock which may be usually harmless is an electrostatic discharge as experienced in everyday life on door handles, car doors etc. These currents can reach values up to 60 A without harmful effects on

7198-403: Is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory , stating that the current passing through

7320-404: Is required, interlock devices may be used to ensure that all electrical sources are removed from the equipment before accessing normally energized parts. Administrative procedures such as lockout–tagout are used to protect workers from accidentally re-energizing equipment under repair. Where accidental contact with energized components is still possible, or where adjustment of an energized system

7442-595: Is sometimes used as an official means of capital punishment in the United States, although its use has become rare from the 1990s onward due to the adoption of lethal injection . Although some original proponents of the electric chair considered it to be a more humane execution method than hanging , shooting , poison gassing , etc., it has now generally been replaced by lethal injections in states that practice capital punishment. Modern reporting has claimed that it sometimes takes several shocks to be lethal, and that

SECTION 60

#1732772492812

7564-531: Is subjected to transients , such as when first energised. The concept of the electric field was introduced by Michael Faraday . An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses , and like it, extends towards infinity and shows an inverse square relationship with distance. However, there

7686-406: Is termed the inductance . The unit of inductance is the henry , named after Joseph Henry , a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes

7808-418: Is that cardiac tissue has a chronaxie (response time) of about 3 milliseconds, so electricity at frequencies of higher than about 333 Hz requires more current to cause fibrillation than is required at lower frequencies. The comparison between the dangers of alternating current at typical power transmission frequencies (i.e., 50 or 60 Hz), and direct current has been a subject of debate ever since

7930-415: Is the farad , named after Michael Faraday , and given the symbol F : one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit

8052-427: Is the main contributor to the impedance of the body in the case of a macroshock —the passing of current between two contact points on the skin. The characteristics of the skin are non-linear however. If the voltage is above 450–600 V, then dielectric breakdown of the skin occurs. The protection offered by the skin is lowered by perspiration , and this is accelerated if electricity causes muscles to contract above

8174-422: Is the reason that a person may be unable to release themselves from the electrical source; if this happens at a height as on a power line they can be thrown off. Larger currents can result in tissue damage and may trigger ventricular fibrillation or cardiac arrest . If death results from an electric shock the cause of death is generally referred to as electrocution . Electric injury occurs upon contact of

8296-529: Is therefore 0 at all places inside the body. This is the operating principal of the Faraday cage , a conducting metal shell which isolates its interior from outside electrical effects. The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between

8418-693: Is unlikely to expose a human to dangerous levels of current. Special isolated power systems may be used in applications such as operating rooms, where electrical equipment must be used in proximity to a person unusually vulnerable to electrical shock. For electrical equipment used outdoors or in wet areas, a residual current device or ground fault circuit interrupter may provide protection from electrical current leakage. Electrical devices have non-conductive insulation preventing contact with energized wires or parts, or may have conductive metal enclosures connected to earth ground so that users will not be exposed to dangerous voltage. Double insulated devices have

8540-409: Is used to energise equipment, and in electronics dealing with electrical circuits involving active components such as vacuum tubes , transistors , diodes and integrated circuits , and associated passive interconnection technologies. The study of electrical phenomena dates back to antiquity, with theoretical understanding progressing slowly until the 17th and 18th centuries. The development of

8662-409: Is usually measured in volts , and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference , and is the energy required to move a unit charge between two specified points. An electric field has

8784-409: Is well established and may be multifactorial. As with any traumatic and life-threatening experience, electrical injury may result in post traumatic psychiatric disorders. There exist several non-profit research institutes that coordinate rehabilitation strategies for electrical injury survivors by connecting them with clinicians that specialize in diagnosis and treatment of various traumas that arise as

8906-536: Is widely used in information processing , telecommunications , and signal processing . Interconnection technologies such as circuit boards , electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system . Today, most electronic devices use semiconductor components to perform electron control. The underlying principles that explain how semiconductors work are studied in solid state physics , whereas

9028-618: The Brazilian military dictatorship (1964 - 1985) is detailed in the final report of the National Truth Commission , published December 10, 2014. The parrilla ( Spanish for 'grill') is a method of torture whereby the victim is strapped to a metal frame and subjected to electric shock. It has been used in a number of contexts in South America. The parrilla was commonly used at Villa Grimaldi ,

9150-721: The Neo-Latin word electricus ("of amber" or "like amber", from ἤλεκτρον, elektron , the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne 's Pseudodoxia Epidemica of 1646. Isaac Newton made early investigations into electricity, with an idea of his written down in his book Opticks arguably

9272-450: The density of the current , tissue resistance and duration of contact. Very small currents may be imperceptible or only produce a light tingling sensation. However, a shock caused by low and otherwise harmless current could startle an individual and cause injury due to jerking away or falling. A strong electric shock can often cause painful muscle spasms severe enough to dislocate joints or even to break bones . The loss of muscle control

9394-423: The electromagnetic force , one of the four fundamental forces of nature. Experiment has shown charge to be a conserved quantity , that is, the net charge within an electrically isolated system will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as

9516-725: The mentally ill and some psychiatrists such as Thomas Szasz have asserted that electroconvulsive therapy (ECT) is torture when used without a bona fide medical benefit against recalcitrant or non-responsive patients. The Judge Rotenberg Center in Canton , Massachusetts has been condemned for torture by the United Nations special rapporteur on torture for its use of electric shocks as punishment as part of its behavior modification program. Japanese serial killer Futoshi Matsunaga used electric shocks to control his victims. Electric shock delivered by an electric chair

9638-522: The quantum revolution. Einstein was awarded the Nobel Prize in Physics in 1921 for "his discovery of the law of the photoelectric effect". The photoelectric effect is also employed in photocells such as can be found in solar panels . The first solid-state device was the " cat's-whisker detector " first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with

9760-452: The strong interaction , but unlike that force it operates over all distances. In comparison with the much weaker gravitational force , the electromagnetic force pushing two electrons apart is 10 times that of the gravitational attraction pulling them together. Charge originates from certain types of subatomic particles , the most familiar carriers of which are the electron and proton . Electric charge gives rise to and interacts with

9882-430: The war of the currents in the 1880s. Animal experiments conducted during this time suggested that alternating current was about twice as dangerous as direct current per unit of current flow (or per unit of applied voltage). It is sometimes suggested that human lethality is most common with alternating current at 100–250 volts; however, death has occurred below this range, with supplies as low as 42 volts. Assuming

10004-545: The 1936 discovery of the Baghdad Battery , which resembles a galvanic cell , though it is uncertain whether the artifact was electrical in nature. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete , in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber. He coined

10126-801: The Abuja grid, while the Ikeja grid caused only 2 deaths. People who survive electrical trauma may develop a host of injuries including loss of consciousness, seizures, aphasia, visual disturbances, headaches, tinnitus, paresis, and memory disturbances. Even without visible burns, electric shock survivors may be faced with long-term muscular pain and discomfort, exhaustion, headache, problems with peripheral nerve conduction and sensation, inadequate balance and coordination, among other symptoms. Electrical injury can lead to problems with neurocognitive function, affecting speed of mental processing, attention, concentration, and memory. The high frequency of psychological problems

10248-656: The Elder and Scribonius Largus , attested to the numbing effect of electric shocks delivered by electric catfish and electric rays , and knew that such shocks could travel along conducting objects. Patients with ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber , could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made

10370-556: The US in 1993, 2.1 deaths per million inhabitants. At that time, the incidence of electrocutions was decreasing. Electrocutions in the workplace make up the majority of these fatalities. From 1980–1992, an average of 411 workers were killed each year by electrocution. Workplace deaths caused by exposure to electricity in the U.S. increased by nearly 24% between 2015 and 2019, from 134 to 166. However, workplace electrical injuries dropped 23% between 2015 and 2019 from 2,480 to 1,900. In 2019,

10492-480: The amount of charge (in mC ) transferred to the body, which makes the amplitude of the electrical stimulus independent of the exact amount of current flowing through the body for very short pulse durations. DC shocks of short duration are usually better tolerated by the heart even at high currents and rarely induce ventricular fibrillation compared to lower currents with longer duration with both DC or AC. The amount of current can easily reach very high values as amperage

10614-558: The arm of a 68-kilogram (150 lb) human can cause powerful muscle contractions; the victim is unable to voluntarily control muscles and cannot release an electrified object. This is known as the "let go threshold" and is a criterion for shock hazard in electrical regulations. The current may, if it is high enough, cause tissue damage or fibrillation which can cause cardiac arrest; more than 30 mA of AC (rms, 60 Hz) or 300–500 mA of DC at high voltage can cause fibrillation. A sustained electric shock from AC at 120 V , 60 Hz

10736-408: The beginning of the field theory of the electric force. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke , Robert Boyle , Stephen Gray and C. F. du Fay . Later in the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of

10858-516: The blood supply to the brain is diminished, which may cause cerebral hypoxia (and its associated neurologic consequences). There are a variety of psychiatric effects that may occur as a result of electrical injuries. Behavioral changes can occur as well, even if the path of electric current did not proceed through the head. Symptoms may include: OSHA found that up to 80 percent of its electrical injuries involve thermal burns due to arcing faults. The arc flash in an electrical fault produces

10980-419: The building it serves to protect. The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work . The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It

11102-426: The charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law , which relates the force to the product of the charges and has an inverse-square relation to the distance between them. The electromagnetic force is very strong, second only in strength to

11224-450: The charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre. The most visible natural occurrence of this is lightning , caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of

11346-520: The current through the body and the duration of the current. Ohm's law states that the current drawn depends on the resistance of the body. The resistance of human skin varies from person to person and fluctuates between different times of day. The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 ohms. Wet or broken skin may drop the body's resistance to 1,000 ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing

11468-411: The current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes

11590-516: The design and construction of electronic circuits to solve practical problems are part of electronics engineering . Faraday's and Ampère's work showed that a time-varying magnetic field created an electric field, and a time-varying electric field created a magnetic field. Thus, when either field is changing in time, a field of the other is always induced. These variations are an electromagnetic wave . Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed

11712-467: The duration and the amount of current passing through the human body. Frequency plays a role with AC and pulse DC. For example, a high frequency current has a higher ventricular fibrillation threshold than lower frequency. Also, shorter single pulses have higher thresholds than short pulses. Below 10 ms are usually believed to have a primarily charge dependent threshold and shock amplitude. Research shows that for very short electric pulse durations below 100 μs

11834-478: The early 19th century had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering . Through such people as Alexander Graham Bell , Ottó Bláthy , Thomas Edison , Galileo Ferraris , Oliver Heaviside , Ányos Jedlik , William Thomson, 1st Baron Kelvin , Charles Algernon Parsons , Werner von Siemens , Joseph Swan , Reginald Fessenden , Nikola Tesla and George Westinghouse , electricity turned from

11956-507: The earth. Current passing through the earth may also provide a hazard of electrical shock, so a ground grid may be installed around installations such as electrical substations . Lightning protection systems are primarily installed to reduce property damage by lightning strikes, but may not entirely prevent electrical shock hazards. Persons outdoors during a lightning storm may be advised to take precautions to avoid electrical shock. Where installation, or maintenance of electrical equipment

12078-427: The effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère , who discovered that two parallel current-carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart. The interaction

12200-448: The electronic electrometer . The movement of electric charge is known as an electric current , the intensity of which is usually measured in amperes . Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current. Electric current can flow through some things, electrical conductors , but will not flow through an electrical insulator . By historical convention,

12322-416: The electrons. However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. The process by which electric current passes through a material is termed electrical conduction , and its nature varies with that of the charged particles and

12444-428: The elementary charge, and any amount of charge an object may carry is a multiple of the elementary charge. An electron has an equal negative charge, i.e. −1.602 176 634 × 10  coulombs . Charge is possessed not just by matter , but also by antimatter , each antiparticle bearing an equal and opposite charge to its corresponding particle. The presence of charge gives rise to an electrostatic force: charges exert

12566-562: The environmental impact of the creation of the Volta Lake on the towns and people bordering the lake. The VRA maintains a national energy supply grid and although it started with hydroelectric power , it is now branching into other types of energy such as thermal energy . The company represents Ghana in the West African Power Pool . Electricity Electricity is the set of physical phenomena associated with

12688-512: The event stated that he was "jolted through the air, and landed across the line", and though rescued by firemen, he sustained burns over 40% of his body and was completely paralyzed except for his eyelids. The shock with the highest voltage reported survived was that of Harry F. McGrew, who came in contact with a 340,000 volt transmission line in Huntington Canyon, Utah. The severity and lethality of electric shocks generally depend on

12810-495: The form of a sine wave . Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance . These properties however can become important when circuitry

12932-404: The heart and lungs. Electric shock which does not lead to death has been shown to cause neuropathy in some cases at the site where the current entered the body. The neurologic symptoms of electrical injury may occur immediately, which traditionally have a higher likelihood for healing, though they may also be delayed by days to years. The delayed neurologic consequences of electrical injury have

13054-689: The heart as the duration is in the order of only several ns . Another example for dangerous electrostatic discharges even without flowing directly through the body are lightning strikes and high voltage arcs. Mechanism of cardiac arrhythmias induced by electricity is not fully understood, but various biopsies have shown arrhythmogenic foci in patchy myocardial fibrosis which contained increased amount of Na+  and K+   pumps , possibly associated with transient and localized changes in sodium-potassium transport as well as their concentrations, resulting in changes in membrane potential . Electric current can cause interference with nervous control, especially over

13176-460: The human body's resistance to 500 ohms". The International Electrotechnical Commission gives the following values for the total body impedance of a hand to hand circuit for dry skin, large contact areas, 50 Hz AC currents (the columns contain the distribution of the impedance in the population percentile ; for example at 100 V 50% of the population had an impedance of 1875Ω or less): The voltage-current characteristic of human skin

13298-479: The large energy (which is proportional to the duration multiplied by the square of the voltage divided by resistance or the square of the current multiplied by the resistance) available from the source. Damage due to current is through tissue heating and/or electroporation injury. For most cases of high-energy electrical trauma, the Joule heating in the deeper tissues along the extremity will reach damaging temperatures in

13420-446: The let-go threshold for a sustained period of time. If an electrical circuit is established by electrodes introduced in the body, bypassing the skin, then the potential for lethality is much higher if a circuit through the heart is established. This is known as a microshock . Currents of only 10  μ A can be sufficient to cause fibrillation in this case with a probability of 0.2%. The voltage necessary for electrocution depends on

13542-400: The material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis , where ions (charged atoms ) flow through liquids, or through plasmas such as electrical sparks. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of

13664-481: The presence and motion of matter possessing an electric charge . Electricity is related to magnetism , both being part of the phenomenon of electromagnetism , as described by Maxwell's equations . Common phenomena are related to electricity, including lightning , static electricity , electric heating , electric discharges and many others. The presence of either a positive or negative electric charge produces an electric field . The motion of electric charges

13786-428: The principle, now known as Faraday's law of induction , that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy. Faraday's disc was inefficient and of no use as

13908-664: The received voltage and current can be controlled with precision and used to cause pain and fear without always visibly harming the victim's body. Electrical torture has been used in war and by repressive regimes since the 1930s. During the Algerian War electrical torture was used by French military forces. Amnesty International published a statement that Russian military forces in Chechnya tortured local women with electric shocks by attaching wires onto their breasts. The use of electric shocks to torture political prisoners of

14030-419: The same type of light radiation from which electric welders protect themselves using face shields with dark glass, heavy leather gloves, and full-coverage clothing. The heat produced may cause severe burns, especially on unprotected flesh. The arc blast produced by vaporizing metallic components can break bones and damage internal organs. The degree of hazard present at a particular location can be determined by

14152-454: The special property that it is conservative , which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated. The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage. For practical purposes, defining

14274-493: The theory of electromagnetism in the 19th century marked significant progress, leading to electricity's industrial and residential application by electrical engineers by the century's end. This rapid expansion in electrical technology at the time was the driving force behind the Second Industrial Revolution , with electricity's versatility driving transformations in both industry and society. Electricity

14396-510: The threshold curve converges into a constant charge criterion independent of peak current or RMS values. Even though the for both muscle and nerve stimulation including the heart and the brain. Heating is primarily determined by the amount of energy and is not related to stimulation. These definitions have been included into the IEC standard 60479-2 in opposite to IEC 60479-1 which addresses longer pulse durations above 10 ms for both DC and AC, which use

14518-583: The top 5 states with the most workplace electrical fatalities were: (1) Texas (608); (2) California (451); (3) Florida (306); (4) New York (273); and (5) Georgia (207). A recent study conducted by the National Coroners Information System (NCIS) in Australia has revealed 321 closed case fatalities (and at least 39 case fatalities still under coronial investigation) that had been reported to Australian coroners where

14640-418: The two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it. Ørsted's words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too. Ørsted did not fully understand his discovery, but he observed

14762-417: The vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together. Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces,

14884-543: Was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves. A hollow conducting body carries all its charge on its outer surface. The field

#811188