what is the s.i unit of electric current
ampere
77117
Electric current An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma). The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter. Electric currents cause Joule heating, which creates light in incandescent light bulbs. They
Electric current
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plural. For a conducting element, electrical resistance "R" and electrical conductance "G" are defined as where "I" is the electric current through the object and "V" is the voltage (electrical potential difference) across the object. The unit siemens for the conductance "G" is defined by where Ω is the ohm, A is the ampere, and V is the volt. For a device with a conductance of one siemens, the electric current through the device will increase by one ampere for every increase of one volt of electric potential difference across the device. The conductance of a resistor with a resistance
Siemens (unit)
2911
are expressed in amperes (as in "the charging current is 1.2 A") and the charge accumulated, or passed through a circuit over a period of time is expressed in coulombs (as in "the battery charge is "). The relation of the ampere (C/s) to the coulomb is the same as that of the watt (J/s) to the joule. The ampere was originally defined as one tenth of the unit of electric current in the centimetre–gram–second system of units. That unit, now known as the abampere, was defined as the amount of current that generates a force of two dynes per
Ampere
7269938
Ampere hour An ampere hour or amp hour (symbol Ah; also denoted A⋅h or A h) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3600 coulombs. The commonly seen "milliampere hour" (mAh or mA⋅h) is one-thousandth of an ampere hour (3.6 coulombs). The ampere hour is frequently used in measurements of electrochemical systems such as electroplating and for battery capacity where the commonly known nominal voltage is dropped. A "milliampere second" (mA⋅s) is a unit of measure
Ampere hour
8000130
to the net movement of electric dipole moments per unit volume, i.e. the polarization P: Similarly with magnetic materials, circulations of the magnetic dipole moments per unit volume, i.e. the magnetization M, lead to magnetization currents: Together, these terms add up to form the bound current density in the material (resultant current due to movements of electric and magnetic dipole moments per unit volume): The total current is simply the sum of the free and bound currents: There is also a displacement current corresponding to the time-varying electric displacement field D: which is an important term in Ampere's circuital law,
Current density
446106
one joule of energy per coulomb of charge that passes through it. It can be expressed in terms of SI base units (m, kg, s, and A) as It can also be expressed as amperes times ohms (current times resistance, Ohm's law), watts per ampere (power per unit current, definition of electric power), or joules per coulomb (energy per unit charge), which is also equivalent to electronvolts per elementary charge: The "conventional" volt, V, defined in 1988 by the 18th General Conference on Weights and Measures and in use from 1990, is implemented using the Josephson effect for exact frequency-to-voltage
Volt
77117
Electric current An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma). The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter. Electric currents cause Joule heating, which creates light in incandescent light bulbs. They
Electric current
2908
Ampere The ampere (; symbol: A), often shortened to "amp", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. The International System of Units defines the ampere in terms of other base units by measuring the electromagnetic force between electrical conductors carrying electric current. The earlier CGS measurement system had two different definitions of current, one essentially the same as the SI's and the other using electric charge as the base unit, with the unit of charge defined by
Ampere
2910
equal to newtons per metre of length. Ampère's force law states that there is an attractive or repulsive force between two parallel wires carrying an electric current. This force is used in the formal definition of the ampere. The SI unit of charge, the coulomb, "is the quantity of electricity carried in 1 second by a current of 1 ampere". Conversely, a current of one ampere is one coulomb of charge going past a given point per second: In general, charge "Q" is determined by steady current "I" flowing for a time "t" as . Constant, instantaneous and average current
Ampere
870028
Henry (unit) The henry (symbol: H) is the SI derived unit of electrical inductance. If a current of 1 ampere flowing through the coil produces flux linkage of 1 weber turn, the coil has a self inductance of 1 henry.‌ The unit is named after Joseph Henry (1797–1878), the American scientist who discovered electromagnetic induction independently of and at about the same time as Michael Faraday (1791–1867) in England. The inductance of an electric circuit is one henry when an electric current that is changing at one ampere per second results in an electromotive force of one volt across the
Henry (unit)
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a fourth base unit alongside the existing three base units. The fourth unit could be chosen to be electric current, voltage, or electrical resistance. Electric current with named unit 'ampere' was chosen as the base unit, and the other electrical quantities derived from it according to the laws of physics. This became the foundation of the MKS system of units. In the late 19th and early 20th centuries, a number of non-coherent units of measure based on the gram/kilogram, centimetre/metre and second, such as the "Pferdestärke" (metric horsepower) for power, the darcy for permeability and "millimetres of mercury" for barometric
International System of Units
2917
Typical circuit breakers will provide 16 A. The current drawn by a number of typical appliances are: Ampere The ampere (; symbol: A), often shortened to "amp", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. The International System of Units defines the ampere in terms of other base units by measuring the electromagnetic force between electrical conductors carrying electric current. The earlier CGS measurement system had two different definitions of current, one essentially the same as the SI's
Ampere
583067
charge of one electron is known to be about 1 C can also be considered the charge of roughly or +1 C the charge of that many positrons or protons, where the number is the reciprocal of . By 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad, but not the coulomb. In 1881, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force, the ampere as the unit for electric current, and the coulomb as the unit of electric charge. At that time,
Coulomb
118226
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 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
Electricity
3991380
EMF, the magnetomotive force formula_1 around a closed loop is defined as: The MMF represents the potential that a hypothetical magnetic charge would gain by completing the loop. The magnetic flux that is driven is not a current of magnetic charge; it merely has the same relationship to MMF that electric current has to EMF. (See microscopic origins of reluctance below for a further description.) The unit of magnetomotive force is the ampere-turn (At), represented by a steady, direct electric current of one ampere flowing in a single-turn loop of electrically conducting material in a vacuum. The gilbert (Gb), established
Magnetic circuit
446105
Volt The volt (symbol: V) is the derived unit for electric potential, electric potential difference (voltage), and electromotive force. It is named after the Italian physicist Alessandro Volta (1745–1827). One volt is defined as the difference in electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the potential difference between two points that will impart
Volt
8000119
Current density In electromagnetism, current density is the electric current per unit area of cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the charges at this point. In SI units, the electric current density is measured in amperes per square metre. Assume that "A" (SI unit: m) is a small surface centred at a given point "M" and orthogonal to the motion of the charges at "M". If "I" (SI unit: A) is the
Current density
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law (one of Maxwell's equations), which relates current density to magnetic field. In special relativity theory, charge and current are combined into a 4-vector. Charge carriers which are free to move constitute a free current density, which are given by expressions such as those in this section. Electric current is a coarse, average quantity that tells what is happening in an entire wire. At position r at time "t", the "distribution" of charge flowing is described by the current density: where J(r, "t") is the current density vector, v(r, "t") is the particles' average drift velocity (SI unit: m∙s), and
Current density
8000127
is the charge density (SI unit: coulombs per cubic metre), in which "n"(r, "t") is the number of particles per unit volume ("number density") (SI unit: m), "q" is the charge of the individual particles with density "n" (SI unit: coulombs). A common approximation to the current density assumes the current simply is proportional to the electric field, as expressed by: where E is the electric field and "σ" is the electrical conductivity. Conductivity "σ" is the reciprocal (inverse) of electrical resistivity and has the SI units of siemens per metre (S⋅m), and E has the SI units of newtons
Current density
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to suggest that the Electric and Magnetic fields are independent, the equation can be rewritten in term of four-current (instead of charge) and a single tensor that represents the combined Electromagnetic field (formula_2) The electric field E is defined such that, on a stationary charge: where "q" is what is known as a test charge. The size of the charge doesn't really matter, as long as it is small enough not to influence the electric field by its mere presence. What is plain from this definition, though, is that the unit of E is N/C (newtons per coulomb). This unit
Classical electromagnetism
13234673
DRG Class ET 171 The DRG Class ET 171 (since 1968 DB Class 471/871) is a three-car electric multiple unit train built for the Hamburg S-Bahn. The first electric Hamburg S-Bahn trains appeared on the Hamburg-Altona City and Suburban Railway in 1907. In 1937, the main-line railway operator, Deutsche Reichsbahn, decided to switch the current collection method from overhead catenary (AC 6,3 kV/25 Hz) to third rail (DC 1,2 kV). The new Class ET 171 trains were built to replace the old overhead line trains. The first unit appeared in Hamburg in December 1939. The first 47 trainsets were built
DRG Class ET 171
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through the closed surface "S" = ∂"V", which is in turn equal to the net current "I": Thus, the conservation of electric charge, as expressed by the continuity equation, gives the result: The charge transferred between times formula_2 and formula_3 is obtained by integrating both sides: where "I" is the net outward current through a closed surface and "Q" is the electric charge contained within the volume defined by the surface. Aside from the properties described in articles about electromagnetism, charge is a relativistic invariant. This means that any particle that has charge "Q", no matter how fast it goes,
Electric charge
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Electrical resistance and conductance The electrical resistance of an object is a measure of its opposition to the flow of electric current. The inverse quantity is , and is the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the notion of mechanical friction. The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S). The resistance of an object depends in large part on the material it is made of—objects made of electrical insulators like rubber tend to have very high resistance and low conductivity, while objects
Electrical resistance and conductance
719512
1 Ω⋅m. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity, and measures a material's ability to conduct an electric current. It is commonly represented by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) or γ (gamma) are also occasionally used. Its SI unit is siemens per metre (S/m). In an ideal case, cross-section and physical composition of the examined material are uniform across the sample, and the electric field and current density are both parallel and constant everywhere. Many resistors and conductors do in fact have a uniform cross section with a uniform
Electrical resistivity and conductivity
15419478
to distinguish the symbol "S" from the lower-case "s" where "second" is meant, potentially causing confusion. So, for example, a pentode’s transconductance of 2.2 mS might alternatively be written as or (most common in the 1930s) or 2.2 mA/V. A handwritten "S" can also be misread as the frequency space variable "s", commonly used in transfer functions. Siemens (unit) The siemens (symbol: S) is the derived unit of electric conductance, electric susceptance and electric admittance in the International System of Units (SI). Conductance, susceptance, and admittance are the reciprocals of resistance, reactance, and impedance respectively; hence one siemens is redundantly
Siemens (unit)
20918252
passing from or to magnetic poles, or forming concentric circles round an electric current. By "line of electric force", I mean the force exerted in the lines joining two bodies, acting on each other according to the principles of static electric induction."Certain conventions are followed when drawing and interpreting electric field lines: The SI unit of the electric field is volt per meter (V/m), or equivalently, newton per coulomb (N/C). In mathematical expressions it is often represented as a vector-valued function formula_5. The electric field can be calculated in many ways, including Gauss' law, Coulomb's law, or Maxwell's equations. The
Introduction to electromagnetism
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hole mobility is defined by the same equation. Both electron and hole mobilities are positive by definition. Usually, the electron drift velocity in a material is directly proportional to the electric field, which means that the electron mobility is a constant (independent of electric field). When this is not true (for example, in very large electric fields), the mobility depends on the electric field. The SI unit of velocity is m/s, and the SI unit of electric field is V/m. Therefore the SI unit of mobility is (m/s)/(V/m) = m/(V·s). However, mobility is much more commonly expressed in cm/(V·s) =
Electron mobility
6802463
single-unit recordings provide the most precise recordings from single neurons. A single unit is defined as a single, firing neuron whose spike potentials are distinctly isolated by a recording microelectrode. The ability to record signals from neurons is centered around the electric current flow through the neuron. As an action potential propagates through the cell, the electric current flows in and out of the soma and axons at excitable membrane regions. This current creates a measurable, changing voltage potential within (and outside) the cell. This allows for two basic types of single-unit recordings. Intracellular single-unit recordings occur within the neuron
Single-unit recording
6770239
Probability current In quantum mechanics, the probability current (sometimes called probability flux) is a mathematical quantity describing the flow of probability in terms of probability per unit time per unit area. Specifically, if one describes the probability density as a heterogeneous fluid, then the probability current is the rate of flow of this fluid. This is analogous to mass currents in hydrodynamics and electric currents in electromagnetism. It is a real vector, like electric current density. The concept of a probability current is a useful formalism in quantum mechanics. In non-relativistic quantum mechanics, the probability current j of the wave
Probability current
2869983
to charge on the left-hand plate is nearly cancelled by the equal but opposite charge on the right-hand plate. Under the assumption of a uniform electric field distribution inside the capacitor, the displacement current density "J" is found by dividing by the area of the surface: where "I" is the current leaving the cylindrical surface (which must equal "I") and "J" is the flow of charge per unit area into the cylindrical surface through the face "R". Combining these results, the magnetic field is found using the integral form of Ampère's law with an arbitrary choice of contour provided the
Displacement current
5983663
the current. Current sheets in plasmas store energy by increasing the energy density of the magnetic field. Many plasma instabilities arise near strong current sheets, which are prone to collapse, causing magnetic reconnection and rapidly releasing the stored energy. This process is the cause of solar flares and is one reason for the difficulty of magnetic confinement fusion, which requires strong electric currents in a hot plasma. An infinite current sheet can be modelled as an infinite number of parallel wires all carrying the same current. Assuming each wire carries current "I", and there are "N" wires per unit length,
Current sheet
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resp. a magnetic field, there is also the possibility of a magnetoelectric susceptibility formula_3 which describes a linear response of the electric polarization to a magnetic field, and vice versa: The tensor formula_6 must be the same in both equations. Here, P is the electric polarization, M the magnetization, E and H the electric and magnetic fields. The SI Unit of α is [s/m] which can be converted to the practical unit [V/(cm Oe)] by [s/m]=1.1 x10 ε [V/(cm Oe)]. For the CGS unit, [unitless] = 3 x 10 [s/m]/(4 x π) The first material where an intrinsic linear magnetoelectric
Magnetoelectric effect
3860992
per unit time in a certain volume is equal to the sum of work done by the field forces and the net outward flux per unit time". Mathematically, this is summarised in differential form as: where ∇•S is the divergence of the Poynting vector (energy flow) and J•E is the rate at which the fields do work on a charged object (J is the current density corresponding to the motion of charge, E is the electric field, and • is the dot product). The energy density "u" is given by: in which B is the magnetic flux density. Using the
Poynting's theorem
77147
electrons into the conduction band. The current-carrying electrons in the conduction band are known as "free electrons", though they are often simply called "electrons" if that is clear in context. Current density is a measure of the density of an electric current. It is defined as a vector whose magnitude is the electric current per cross-sectional area. In SI units, the current density is measured in amperes per square metre. where "formula_6" is current in the conductor, formula_7 is the current density, and formula_8 is the differential cross-sectional area vector. The current density (current per unit area) "formula_7" in materials
Electric current
3189460
of force are perpendicular to the direction of the electric current, which may be either alternating current (AC) or some form of direct current (DC) (rectified AC). The presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak, since air cannot support as much magnetic field per unit volume as metals. To identify a leak, ferrous particles, either dry or in a wet suspension, are applied to a part. These are attracted to an area of flux leakage and form what is known as an indication, which is evaluated to determine its nature, cause,
Magnetic particle inspection
77128
wire he deduced that the heat produced was proportional to the square of the current multiplied by the electrical resistance of the wire. This relationship is known as Joule's First Law. The SI unit of energy was subsequently named the joule and given the symbol "J". The commonly known unit of power, the watt, is equivalent to one joule per second. In an electromagnet a coil, of a large number of circular turns of insulated wire, wrapped on a cylindrical core, behaves like a magnet when an electric current flows through it. When the current is switched off, the coil
Electric current
4256658
line was electrified with overhead lines supplying alternating current at 6.6 kV, 25 Hz. The electricity came from a coal-fired power station in "Leverkusenstraße" in Bahrenfeld, which also provided power to the Altona harbour railway. The first electric trains ran on 1 October 1907, and from 29 January 1908 the line from Blankenese to Ohlsdorf was served exclusively by electric trains. These dates are considered the birthdates of the S-Bahn. The basic unit of an AC train consisted of two articulated compartment carriages on six axles with motorised two-axle bogies under each cab end and a Jacobs bogie in the
Hamburg S-Bahn
7410925
vowel of the prefixed units kiloohm and megaohm is commonly omitted, producing kilohm and megohm. In alternating current circuits, electrical impedance is also measured in ohms. The siemens (symbol: S) is the SI derived unit of electric conductance and admittance, also known as the mho (ohm spelled backwards, symbol is ℧); it is the reciprocal of resistance in ohms (Ω). The power dissipated by a resistor may be calculated from its resistance, and the voltage or current involved. The formula is a combination of Ohm's Law and Joule's law: where: A linear resistor has a constant resistance value over all
Ohm
395724
of numbers, called the complex numbers, that does contain solutions to the square root of a negative number. This is done by introducing a new number, denoted by "i" (sometimes "j", especially in the context of electricity where ""i"" traditionally represents electric current) and called the imaginary unit, which is "defined" such that . Using this notation, we can think of "i" as the square root of −1, but notice that we also have and so −"i" is also a square root of −1. By convention, the principal square root of −1 is "i", or more generally, if "x" is
Square root
77118
also create magnetic fields, which are used in motors, inductors and generators. The moving charged particles in an electric current are called charge carriers. In metals, one or more electrons from each atom are loosely bound to the atom, and can move freely about within the metal. These conduction electrons are the charge carriers in metal conductors. The conventional symbol for current is , which originates from the French phrase "intensité du courant", (current intensity). Current intensity is often referred to simply as "current". The symbol was used by André-Marie Ampère, after whom the unit of electric current is named,
Electric current
7410929
of current that gives a specified force between two wires, or a unit of charge that gives a unit of force between two unit charges. This latter method ensures coherence with the units of energy. Defining a unit for resistance that is coherent with units of energy and time in effect also requires defining units for potential and current. It is desirable that one unit of electrical potential will force one unit of electric current through one unit of electrical resistance, doing one unit of work in one unit of time, otherwise all electrical calculations will require conversion factors. Since
Ohm
17751303
Plug-in electric vehicles in Canada Cumulative sales of plug-in electric cars in Canada passed the 20,000 unit mark in May 2016, and the 30,000 unit mark in January 2017. The Chevrolet Volt, released in 2011, is the all-time top selling plug-in electric vehicle in the country, with cumulative sales of 6,387 units through May 2015 (representing over 30% of all plug-in cars sold in the country). Ranking second is the Tesla Model S with 4,160 units sold through April 2016, followed by the Nissan Leaf with 3,692 units delivered . The Model S was the top selling plug-in electric car
Plug-in electric vehicles in Canada
3609310
ventilation slots, though some have provision for forced air cooling from an external supply. Hysteresis and Eddy Current dynamometers are two of the most useful technologies in small ( and less) dynamometers. Electric motor/generator dynamometers are a specialized type of adjustable-speed drive. The absorption/driver unit can be either an alternating current (AC) motor or a direct current (DC) motor. Either an AC motor or a DC motor can operate as a generator that is driven by the unit under test or a motor that drives the unit under test. When equipped with appropriate control units, electric motor/generator dynamometers can be
Dynamometer
9316160
(1KU - 023). The unit has two handles. They are: Reversive - features Reverse, Drive, and Neutral positions. Main - features neutral, maneuvering, and 4 working positions. Traction engines and most of electrical devices are manufactured by the Electric Equipment plant of Riga. Unit: Phase Splitters Placed: Under the body of Motor cars. Purpose: Converts single phase 220 V Current into 3 phase. The produced current serves for powering various supplementary machines. Unit: Fan wheel. Placed: On splitter's rotor(?). Purpose: Cooling rectifiers, reactors, and transformers. The rotational frequency of the splitter is 1495 rpm. Unit: Motor - Compressor. Composition: LOSV-72-6
ER9 electric trainset
15419474
Siemens (unit) The siemens (symbol: S) is the derived unit of electric conductance, electric susceptance and electric admittance in the International System of Units (SI). Conductance, susceptance, and admittance are the reciprocals of resistance, reactance, and impedance respectively; hence one siemens is redundantly equal to the reciprocal of one ohm, and is also referred to as the "mho". The 14th General Conference on Weights and Measures approved the addition of the siemens as a derived unit in 1971. The unit is named after Ernst Werner von Siemens. In English, the same form "siemens" is used both for the singular and
Siemens (unit)
3660371
N/(C·m/s). The dividing factor between the two types of field is metres per second (m/s), which is velocity. This relationship immediately highlights the fact that whether a static electromagnetic field is seen as purely magnetic, or purely electric, or some combination of these, is dependent upon one's reference frame (that is, one's velocity relative to the field). In ferromagnets, the movement creating the magnetic field is the electron spin (and to a lesser extent electron orbital angular momentum). In a current-carrying wire (electromagnets) the movement is due to electrons moving through the wire (whether the wire is straight or circular).
Tesla (unit)
5044434
of the Soviet Union Vice Admiral G. I. Schedrin. The commission determined not only the immediate causes of the boat's loss, but also that two further errors had compounded the accident: the crew never attempted to shift propulsion to the electric motors, and they never performed an emergency ballast tank blow. Soviet submarine S-80 S-80 was a diesel-electric submarine of the Soviet Navy. Its keel was laid down on 13 March 1950 at Krasnoye Sormovo as a Project 613 unit (NATO : ). It was launched on 21 October, and delivered to Baku on the Caspian Sea on 1 November
Soviet submarine S-80
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Diesel Electric Multiple Unit (DEMU), but were withdrawn after a few years. Initially the test unit was formed for trials on the 750 V direct current (DC) third rail system of the Southern Region, and was numbered 457001. As with all Southern Region electric multiple units only the last four digits of the unit number were actually carried. The unit formation was: Later, the unit was altered to undertake trials on the 25 kV alternating current (AC) overhead wire system used on electrified lines north of the River Thames. The unit was renumbered as a Class 316 unit, number 316999.
British Rail Classes 316 and 457
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any of the Current Collector Device sheared off the bogie. As the Current Collector Device supplies power to the train via the third rail, it allows timely action to be taken if any of the Collector Shoe is dislodged. The C151C trains are the fifth commuter type Electric Multiple Unit (EMU) made in Japan to feature electric systems fully manufactured by Fuji Electric. Propulsion is controlled by VVVF Inverter with 2-level IGBT semiconductor controller, rated at 415 kV. Each inverter unit controls two motors on one bogie (1C2M), and one motor car features two of such units. Motors are three-phase
Kawasaki Heavy Industries & CRRC Sifang C151C
9055740
Load banks are used in a variety of applications, including: The three most common types of load banks are resistive, inductive, and capacitive. Both inductive and capacitive loads create what is known as reactance in an AC circuit. Reactance is a circuit element's opposition to an alternating current, caused by the buildup of electric or magnetic fields in the element due to the current and is the "imaginary" component of impedance, or the resistance to AC signals at a certain frequency. Capacitive reactance is equal to 1/(2⋅π⋅f⋅C), and inductive reactance is equal to 2⋅π⋅f⋅L. The unit of reactance is the
Load bank
361827
derived quantities can be specified in terms of the SI base and derived units that have no named units in the SI system, such as acceleration, which is defined in SI units as m/s. The SI base units are the building blocks of the system and all the other units are derived from them. When Maxwell first introduced the concept of a coherent system, he identified three quantities that could be used as base units: mass, length and time. Giorgi later identified the need for an electrical base unit, for which the unit of electric current was chosen for SI.
International System of Units
2840962
the vector potential. This leads to the definition of the magnetic dipole moment as: where × is the vector cross product, is the position vector, and is the electric current density and the integral is a volume integral. When the current density in the integral is replaced by a loop of current I in a plane enclosing an area S then the volume integral becomes a line integral and the resulting dipole moment becomes which is how the magnetic dipole moment for an Amperian loop is derived. Practitioners using the current loop model generally represent the magnetic field by the
Magnetic moment
13989192
heat is generated. By regulating the amount of current conducted and the level of resistance encountered, the amount of heat produced can be predetermined and controlled. Electrical resistance (usually described as a material's opposition to the flow of an electric current) is used to convert electric energy into thermal energy as an electric current ("I") conducted through a material with resistance ("R") releases power ("P") equal to "P" = "I""R", where "P" is the power measured in watts, "I" is the current measured in amperes and "R" is the resistance measured in ohms. Resistance soldering is unlike using a conduction
Soldering
2132510
disk-shaped reaction mass expands into a far more efficient cigar-shaped wave of plasma debris. The cigar shape focuses much of the plasma to impinge onto the pusher-plate. The maximum effective specific impulse, "I", of an Orion nuclear pulse drive generally is equal to: where "C" is the collimation factor (what fraction of the explosion plasma debris will actually hit the impulse absorber plate when a pulse unit explodes), "V" is the nuclear pulse unit plasma debris velocity, and "g" is the standard acceleration of gravity (9.81 m/s; this factor is not necessary if "I" is measured in N·s/kg or m/s).
Project Orion (nuclear propulsion)
5962768
can deduce what is fundamental and what is not, the notion of what is elementary and what is composite is merely relative, acting as it were as a kind of gauge symmetry. This seems to favour the view of emergentism, as both the Noether charge (particle) and topological charge (soliton) have the same ontology. Several notable physicists underlined the implications of duality: Montonen–Olive duality Montonen–Olive duality or electric-magnetic duality is the oldest known example of strong-weak duality or S-duality according to current terminology. It generalizes the electro-magnetic symmetry of Maxwell's equations by stating that magnetic monopoles, which are usually viewed
Montonen–Olive duality
4294840
presence of both a charge density ρ(r, "t") and current density J(r, "t"), there will be both an electric and a magnetic field, and both will vary in time. They are determined by Maxwell's equations, a set of differential equations which directly relate E and B to the electric charge density (charge per unit volume) "ρ" and current density (electric current per unit area) J. Alternatively, one can describe the system in terms of its scalar and vector potentials "V" and A. A set of integral equations known as "retarded potentials" allow one to calculate "V" and A from ρ
Classical field theory
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Low current densities produce spectral line emission and tend to favour longer wavelengths. High current densities produce continuum emission and tend to favour shorter wavelengths. Low current densities for flash lamps are generally around 10 A⋅mm. High current densities can be more than 40 A⋅mm. Current density In electromagnetism, current density is the electric current per unit area of cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the charges at this point. In SI
Current density
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among them can be represented by vectors or expressed using complex numbers, "S" = "P" + "j Q" (where "j" is the imaginary unit). The formula for complex power (units: VA) in phasor form is: formula_2, where "V" denotes voltage in phasor form, with the amplitude as rms, and "I" denotes current in phasor form, with the amplitude as rms. Also by convention, the complex conjugate of "I" is used, which is denoted formula_3 (or formula_4), rather than "I" itself. This is done such that a leading current (capacitive load, negative reactance) results in negative reactive power. Other forms of
AC power
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intensity E by some factor q has the same consequences as lowering gas density N by factor q. Its SI unit is V·cm, but the Townsend unit (Td) is frequently used. The use of a glow discharge for solution of certain mapping problems was described in 2002. Electric discharge in gases Electric discharge in gases occurs when electric current flows through a gaseous medium due to ionization of the gas. Depending on several factors, the discharge may radiate visible light. The properties of electric discharges in gases are studied in connection with design of lighting sources and in the design
Electric discharge in gases
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utility vans in the world, with the U.S. leading plug-in electric car sales with a 45% share of global sales. In September 2014, sales of plug-in electric cars in the United States reached the 250,000 unit milestone. Global cumulative sales of the Tesla Model S passed the 50,000 unit milestone in October 2014. In November 2014 the Renault–Nissan Alliance reached 200,000 all-electric vehicles delivered globally, representing a 58% share of the global light-duty all-electric market segment. The world's top selling all-electric cars in 2014 were the Nissan Leaf (61,507), Tesla Model S (31,655), BMW i3 (16,052), and the Renault Zoe
History of the electric vehicle
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the divergence of the electromagnetic displacement, defined as then Four-current In special and general relativity, the four-current (technically the four-current density) is the four-dimensional analogue of the electric current density. Also known as vector current, it is used in the geometric context of "four-dimensional spacetime", rather than three-dimensional space and time separately. Mathematically it is a four-vector, and is Lorentz covariant. Analogously, it is possible to have any form of "current density", meaning the flow of a quantity per unit time per unit area. see current density for more on this quantity. This article uses the summation convention for indices.
Four-current
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Four-current In special and general relativity, the four-current (technically the four-current density) is the four-dimensional analogue of the electric current density. Also known as vector current, it is used in the geometric context of "four-dimensional spacetime", rather than three-dimensional space and time separately. Mathematically it is a four-vector, and is Lorentz covariant. Analogously, it is possible to have any form of "current density", meaning the flow of a quantity per unit time per unit area. see current density for more on this quantity. This article uses the summation convention for indices. See covariance and contravariance of vectors for background on
Four-current
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Persistent current Persistent current is a perpetual electric current, not requiring an external power source. In electromagnetism, all magnetizations can be seen as microscopic persistent currents. By definition a magnetization formula_1 can be replaced by its corresponding microscopic form, which is an electric current density: This current is a bound current, not having any charge accumulation associated with it since it is divergenceless. What this means is that any permanently magnetized object, for example a piece of lodestone, can be considered to have persistent electric currents running throughout it (the persistent currents are generally concentrated near the surface). The converse
Persistent current
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global electric vehicle sales passed the 250,000 unit milestone also in August 2016. Renault global electric vehicle sales passed the 100,000 unit milestone in early September 2016. Global sales of the Tesla Model X passed the 10,000 unit mark in August 2016, with most cars delivered in the United States. Cumulative global sales of pure electric passenger cars and utility vans passed the 1 million unit milestone in September 2016. Global sales of the Tesla Model S achieved the 150,000 unit milestone in November 2016, four years and five months after its introduction, and just five more months than it
History of the electric vehicle
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chopper-based electronics. ZiU-5 is a high-floor big class trolleybus for city mass transit. It's duraluminium hull mounted on the steel frame and carcass constructions. The hull has two doors in its front and rear ends. The doors open and close automatically by electric gear under driver's control. The vehicle is powered by DK-207A 95-kilowatt electric motor. The current regulation system (controller unit) is an automatic indirect one. All commutation of power-circuit resistors is performed by a low-voltage electric servomotor. These resistors limit the electric current through the main motor and, therefore, regulate its speed and torque. ZiU-5 is equipped with
ZiU-5
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Weber defined the absolute unit of electrical resistance (which was named the ohm after Georg Ohm). Weber's name is now used as a unit name to describe magnetic flux, the weber. German physicist Johann Hittorf concluded that "ion movement" caused electric current. In 1853 Hittorf noticed that some ions traveled more rapidly than others. This observation led to the concept of transport number, the rate at which particular ions carried the electric current. Hittorf measured the changes in the concentration of electrolysed solutions, computed from these the transport numbers (relative carrying capacities) of many ions, and, in 1869, published his
History of electrochemistry
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Voltameter A voltameter or coulometer is a scientific instrument used for measuring quantity of electricity (electric charge) through electrolytic action. The SI unit of quantity of electricity is the coulomb. The voltameter should not be confused with a voltmeter, which measures electric potential. The SI unit for electric potential is the volt. The voltameter is an electrolytic cell and the measurement is made by weighing the element deposited or released at the cathode in a specified time. This is the most accurate type. It consists of two silver plates in a solution of silver nitrate. When current is flowing, silver
Voltameter
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hybrid mix of hydraulic and mechanical transmissions, usually reverting to the latter at higher operating speeds as this decreases engine RPM and noise. In a diesel–electric multiple unit (DEMU), a diesel engine drives an electrical generator or an alternator which produces electrical energy. The generated current is then fed to electric traction motors on the wheels or bogies in the same way as a conventional diesel–electric locomotive. In modern DEMUs, such as the Bombardier Voyager family, each car is entirely self-contained and has its own engine, generator and electric motors. In older designs, such as the British Rail Class 207,
Diesel multiple unit
7700033
the total charge or a constant current. These devices invented by Michael Faraday were used frequently in the 19th century and in the first half of the 20th century. In the past, the coulometers of that type were named voltameters. Voltameter A voltameter or coulometer is a scientific instrument used for measuring quantity of electricity (electric charge) through electrolytic action. The SI unit of quantity of electricity is the coulomb. The voltameter should not be confused with a voltmeter, which measures electric potential. The SI unit for electric potential is the volt. The voltameter is an electrolytic cell and the
Voltameter
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device formula_8 across the electrodes (enclosing it). On the other side gives the increment of the internal energy formula_86 in formula_8 in a unit of time, formula_88 being the total electric field of which formula_89 is due the electrodes and formula_90 is due to the whole charge density in formula_8 with formula_92 over "S". Then it is formula_93, so that, according to such equations, we also verify the energy balance formula_94 by means of the electrokinematics theorem. With the above relationships the balance can be extended also to the open devices by taking into account the displacement current across formula_32.
Electrokinematics theorem
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traction current to motors on both cars. The multiple unit traction control system was developed by Frank Sprague and first applied and tested on the South Side Elevated Railroad (now part of the Chicago 'L') in 1897. In 1895, derived from his company's invention and production of direct current elevator control systems, Frank Sprague invented a multiple unit controller for electric train operation. This accelerated the construction of electric traction railways and trolley systems worldwide. Each car of the train has its own traction motors: by means of motor control relays in each car energized by train-line wires from the
Multiple-unit train control
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the statement: for any closed surface "S". While the magnetic flux through a closed surface is always zero, the magnetic flux through an open surface need not be zero and is an important quantity in electromagnetism. For example, a change in the magnetic flux passing through a loop of conductive wire will cause an electromotive force, and therefore an electric current, in the loop. The relationship is given by Faraday's law: where The two equations for the EMF are, firstly, the work per unit charge done against the Lorentz force in moving a test charge around the (possibly moving) surface
Magnetic flux
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current electric power began on June 17, 1972. One unit of the Kettle generating station was completed before the direct current converters were completed. For the winter of 1970 the bipole lines were energized with alternating current, contributing a useful amount of energy to the Manitoba system; a shunt reactor was installed to prevent excess voltage rise due to the Ferranti effect. At that time, Bipole I used the world's highest operating voltage to deliver the largest amount of power from a remote site to a city, and employed the largest mercury arc valves ever developed for such an application.
Nelson River DC Transmission System
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the unit is here for any division that needs additional manpower, equipment, or just some simple advice. By maintaining a network of contacts within the law enforcement and criminal justice community, the ACT-T unit will find a solution to every problem no matter what the situation. CPSO has approximately 11 K9's with dual purpose K'9's assisting each patrol shift day and night. Other K-9 units are dedicated to criminal interdiction work on the 44miles of jurisdiction on I-10 from Jeff Davis parish line to the Texas state line. Other K9's are allocated to the jail as well as the drug
Calcasieu Parish Sheriff's Office
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will have USB ports installed in each alternating current electrical outlet, as well as powered bathroom doors, stainless steel urinals in each bathroom, and Gorilla Glass side windows that do not haze, fade or crystallize. The M9 and M9A will come equipped with new announcements that are easier to hear and differ from the current ones used on the M7, M8, and C3 fleets. M9 (railcar) The M9 and M9A are electric multiple unit railroad cars being built by Kawasaki Heavy Industries for use on the Metropolitan Transportation Authority (MTA)'s Long Island Rail Road (LIRR) and Metro-North Railroad. These cars
M9 (railcar)
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WJZ (AM) WJZ (1300 AM) is a sports radio station operating on 1300 kHz and licensed to Baltimore, Maryland with transmitter operations in Windsor Mill. Established in 1922 as WEAR, the station is owned by Entercom and broadcasts the CBS Sports Radio network full-time. The WJZ callsign was first used on what is now WABC in New York City. The original Westinghouse Electric Corporation, whose broadcasting division is a predecessor to the current broadcasting unit of CBS Corporation, launched WJZ in 1921, and was located originally in Newark, New Jersey. WJZ was sold in 1923 to the Radio Corporation of
WJZ (AM)
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Abcoulomb The abcoulomb (abC or aC) or electromagnetic unit of charge (emu of charge) is the basic physical unit of electric charge in the cgs-emu system of units. One abcoulomb is equal to ten coulombs. CGS-emu (or "electromagnetic cgs") units are one of several systems of electromagnetic units within the centimetre gram second system of units; others include CGS-esu, Gaussian units, and Lorentz–Heaviside units. In these other systems, the abcoulomb is "not" used; CGS-esu and Gaussian units use the statcoulomb is instead, while the Lorentz-Heaviside unit of charge has no specific name. In the electromagnetic cgs system, electric current is
Abcoulomb
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current' to propel the interaction between the musicians. She later created a version of the piece for two violins and loudspeaker which was premiered by the Riot Ensemble in London on May 14, 2018. In an interview with Tim Rutherford-Johnson, Cleare described the work:At the centre of two of the spatially divided chamber groups lies a solo violin. I think of both solo violins as ‘electric currents’, wiry voices that magnetically charge the electricity of the ensemble that surrounds them, wrapping layers of various sonic materials around the violins, providing what I think of as an electric cloud for the
Ann Cleare
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charged particle nor on electrons in a solid electrical wire, but on a continuous charge distribution in motion, it is a "volumetric" (body) force, a force per unit volume: where f is the "force density" (force per unit volume), "ρ" the charge density (charge per unit volume), E the electric field, J the current density (current per unit area) and B the magnetic field. MHD thrusters are classified in two categories according to the way the electromagnetic fields operate: As induction MHD accelerators are electrodeless, they do not exhibit the common issues related to conduction systems (especially Joule heating, bubbles
Magnetohydrodynamic drive
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the Tesla charging equipment was plugged in. Shortly afterwards, Tesla updated the Model S firmware to reduce charging current when power fluctuations were detected and replaced wall adapters with a new unit containing a thermal fuse. On November 18, 2013, Tesla released a software update to the air suspension system to increase the ground clearance at highway speeds and requested that the NHTSA conduct an investigation into the fire incidents. Another fire incident took place in Toronto, Canada, in early February 2014. The Model S was parked in a garage and it was not plugged in or charging when the
Plug-in electric vehicle fire incidents
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out to assist the disabled fishing vessel "Theodora". At the same time, 30 miles east of Chincoteague, the 605-foot coal freighter "Marine Electric" reported that she was taking on water. After escorting the "Theodora" to Chincoteague Inlet, "Point Highland" raced to answer the "Marine Electric"'s distress call. Battling 30-foot seas, 40 knot winds, and below-freezing temperatures, she arrived on scene and began what proved to be a futile search for survivors. "Point Highland" then recovered 17 bodies. She was awarded her second Unit Commendation for these actions. On 26 December 1985 "Point Highland" again distinguished herself in a marathon rescue
USCGC Point Highland (WPB-82333)
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trains entered service with the plan being that these trains would replace the S sets, although it was revealed in 2013 that some S sets would stay. In October 2012 a new service from Bathurst to Sydney commenced. At the time of it cessation in June 2013, CityRail operated eight electric multiple unit classes for suburban and interurban working and two diesel multiple unit classes. All CityRail electric trains used 1500 V DC overhead electrification and travel on 1,435mm standard gauge tracks. Double deck rollingstock was first introduced in 1964 and after 1996, all electric multiple units were double deck.
CityRail
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buss which will also have their own associated control relays. For obvious safety reasons these relays are all normally open. The battery pack also contains a variety of temperature, voltage, and current sensors. Collection of data from the pack sensors and activation of the pack relays are accomplished by the pack ’s Battery Monitoring Unit (BMU) or Battery Management System (BMS). The BMS is also responsible for communications with the world outside the battery pack. Batteries in BEVs must be periodically recharged. BEVs most commonly charge from the power grid (at home or using a street or shop recharging point),
Electric vehicle battery
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One thing led to another and eventually a few weeks later he built the first alternating current measuring meter. He patented it under number US449003 A. It was a type of motor. Shallenberger's meter device was improved to what is today the modern electric meter for recording and indicating watt-hours for the measure of electric energy consumed by a customer. His electric meter was used by the British Government Board of Trade as the primary instrument for the measurement of electric current. His electric meter for measuring alternating current electricity was known worldwide by the end of the nineteenth century.
Oliver B. Shallenberger
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and pollution-free operation. Being quieter than diesel multiple units (DMUs) and locomotive-hauled trains, EMUs can operate later at night and more frequently without disturbing nearby residents. In addition, tunnel design for EMU trains is simpler as no provision is needed for exhausting fumes, although retrofitting existing limited-clearance tunnels to accommodate the extra equipment needed to transmit electric power to the train can be difficult. Multiple unit train control was first used in the 1890s. The Liverpool Overhead Railway opened in 1893 with two car electric multiple units, controllers in cabs at both ends directly controlling the traction current to motors
Electric multiple unit
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it possible to measure the rings in a clean electromagnetic environment over a large range of magnetic field and also to measure a number of rings on one sample chip. Persistent current Persistent current is a perpetual electric current, not requiring an external power source. In electromagnetism, all magnetizations can be seen as microscopic persistent currents. By definition a magnetization formula_1 can be replaced by its corresponding microscopic form, which is an electric current density: This current is a bound current, not having any charge accumulation associated with it since it is divergenceless. What this means is that any permanently
Persistent current
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CBT in the UK It uses a 400A DC wave controller with regenerative braking to increase efficiency. The electric motor is a 19 kW 17" high output hub motor. It is air cooled and brushless. The hub design allows better cooling, a decreased chance of overheating/warping the casing and increases the life span of the unit. Urban S The Urban S is an electric motorcycle made by Evoke Motorcycles and is Evoke's first production model to be sold worldwide The Urban S has been on sale in China since summer 2015 and is scheduled for release in selected European countries
Urban S
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proliferation. The waste would contain significantly reduced concentrations of long-lived, weapons-usable actinides per gigawatt-year of electric energy produced compared to the waste from a LWR. In addition, there would be about 20 times less waste per unit of electricity produced. This offers the potential to efficiently use the very large stockpiles of enriched fissile materials, depleted uranium, and spent nuclear fuel. In contrast to current commercial fission reactors, hybrid reactors potentially demonstrate what is considered inherently safe behavior because they remain deeply subcritical under all conditions and decay heat removal is possible via passive mechanisms. The fission is driven by
Nuclear fusion–fission hybrid
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Ohm's law which has units of volts), "J" is the current density vector with units of amperes per unit area (analogous to "I" of Ohm's law which has units of amperes), and "ρ" (Greek "rho") is the resistivity with units of ohm·meters (analogous to "R" of Ohm's law which has units of ohms). The above equation is sometimes written as J = formula_19E where "σ" (Greek "sigma") is the conductivity which is the reciprocal of ρ. The voltage between two points is defined as: with formula_21 the element of path along the integration of electric field vector E. If the
Ohm's law
6898648
on both cars. The multiple unit traction control system was developed by Frank Sprague and first applied and tested on the South Side Elevated Railroad (now part of the Chicago 'L') in 1897. In 1895, derived from his company's invention and production of direct current elevator control systems, Frank Sprague invented a multiple unit controller for electric train operation. This accelerated the construction of electric traction railways and trolley systems worldwide. Each car of the train has its own traction motors: by means of motor control relays in each car energized by train-line wires from the front car all of
Electric multiple unit
4915588
the multinational electrical equipment corporation ABB Group and the Finnish shipbuilder Masa-Yards for the development of a new type of electric propulsion unit. Prior to this, the companies had been working together for decades in the field of diesel-electric propulsion systems and in the 1980s produced the first icebreakers with alternating current propulsion motors and cycloconverters. The development of the prototype started in 1989 and the first unit was ready for installation in the following year. The 1.5MW unit, dubbed "Azipod" (short for azimuthing electric podded drive) was installed on the 1979-built Finnish fairway support vessel "Seili" at Hietalahti shipyard
Azipod
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I Call Music II" in 1984 through to "Now That's What I Call Music! 81" in 2012. Jenny Fisher took over as the compiler beginning with "Now That's What I Call Music! 82". On 23 October 2013, the NOW Music television channel was launched in the UK. Targeting a broad age group, the channel used to play current popular music in the daytime and hits from its 30-year back catalogue in the evenings. It was renamed on 27 December 2016 as Now 80s. On 27 December 2017, Now 90s replaced Chilled TV. The most successful volume to date is 1999's
Now That's What I Call Music!
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Corporation, which operated as M&I Bank. Prior to acquisition, M&I was Wisconsin's largest and oldest bank, with branches in Wisconsin, Minnesota, Missouri, Kansas, Arizona and the Indianapolis market. When the transaction completed, M&I Bank, along with current Harris Bank branches were rebranded BMO Harris Bank. In January 2011, BMO announced the purchase of Hong Kong-based Lloyd George Management. Lloyd George has offices in Hong Kong, London (UK), Singapore, Mumbai and Florida and manages a portfolio of approximately US$6 billion. In September 2015, BMO agreed to acquire General Electric Co. subsidiary GE Capital's transportation-finance unit. The business acquired has USD $8.7-billion
Bank of Montreal
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vehicle in the American market to achieve the 100,000 unit sales milestone. Leaf sales achieved the 100,000 unit milestone in October 2016, becoming the first all-electric vehicle in the country to pass that mark. The Model S achieved the mark of 100,000 sales in the U.S. in June 2017, launched in June 2012, the Model S hit this milestone quicker than both the Volt and the Leaf. The Tesla Model 3 reached the 100,000 unit milestone in November 2018, launched in July 2017, it hit this milestone quicker than any previous model sold in the U.S. During 2013 sales were
Plug-in electric vehicles in the United States
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Frankfurt Motor Show and has an all-electric range of . Production of both plug-in electric cars was scheduled to start in Leipzig in 2013. Global i3 sales passed the 25,000 unit milestone in May 2015. Combined global sales of the BMW i brand models passed the 30,000 mark in June 2015, and the 50,000 unit milestone in January 2016. Global sales of the BMW i3 achieved the 50,000 unit milestone in July 2016. , BMW expects a stable development in the plug-in electric market with low profits the next 5-7 years, until batteries have doubled their capacity, with the goal
BMW i
550544
complete lattice generated by some set "S" is just the powerset 2, i.e. the set of all subsets of "S", ordered by subset inclusion. The required unit "i":"S"→2 maps any element "s" of "S" to the singleton set {"s"}. Given a mapping "f" as above, the function "f"°:2→"M" is defined by Then "f"° transforms unions into suprema and thus preserves joins. Our considerations also yield a free construction for morphisms that do preserve meets instead of joins (i.e. upper adjoints of Galois connections). In fact, we merely have to dualize what was said above: free objects are given as powersets
Complete lattice
118182
electric current and produces a magnetic field. When a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. Thus, if that charge were to move, the electric field would be doing work on the electric charge. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is typically
Electricity
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the domain of the "i"-th current basis function, thereby completing the quadratic form) produces the "i"-th row of the matrix eigenvalue equation for a 3-dimensional array of PEC scatterers as: As in all MoM formulations, the reaction concept in electromagnetics (Rumsey [1954], Harrington [1961]) was used in obtaining this equation. The electric field boundary/continuity conditions are "tested" (or enforced) by being integrated against electric current basis functions (for dielectric structures, the magnetic field continuity conditions are additionally tested by being integrated against magnetic current basis functions), and this is how the electric (and magnetic) field boundary conditions are converted into
Bloch wave – MoM method
19745086
maintain quasineutrality. As a result of the ensuing electric field, the ions are accelerated downstream, while all electrons except the more energetic ones are confined upstream. In this way, the electric field helps convert the electron internal energy into directed ion kinetic energy. In steady-state operation, the exhausted plasma jet is globally current-free, i.e., the total ion current and electron current at each section are equal. This condition prevents the continuous electrical charging of the spacecraft on which the magnetic nozzle is mounted, which would result if the amount of ions and electrons emitted per unit time differ. The electron
Magnetic nozzle
77135
an electric current." When a metal wire is connected across the two terminals of a DC voltage source such as a battery, the source places an electric field across the conductor. The moment contact is made, the free electrons of the conductor are forced to drift toward the positive terminal under the influence of this field. The free electrons are therefore the charge carrier in a typical solid conductor. For a steady flow of charge through a surface, the current "I" (in amperes) can be calculated with the following equation: where "Q" is the electric charge transferred through the surface
Electric current
956299
diesel-mechanical (DMMU) or diesel-hydraulic (DHMU). The term "multiple unit" does not denote locomotives using multiple-unit train control. Multiple unit train control was first used in electric multiple units in the 1890s. The Liverpool Overhead Railway opened in 1893 with two car electric multiple units, controllers in cabs at both ends directly controlling the traction current to motors on both cars. The multiple unit traction control system was developed by Frank Sprague and first applied and tested on the South Side Elevated Railroad (now part of the Chicago 'L') in 1897. In 1895, derived from his company's invention and production of
Multiple unit