All physical quantities and their designations. School curriculum: what is n in physics? Electricity and magnetism. Units of measurement of physical quantities
Drawing drawings is not an easy task, but you can’t do without it in the modern world. After all, in order to make even the most ordinary item (a tiny bolt or nut, a shelf for books, the design of a new dress, etc.), you first need to carry out the appropriate calculations and draw a drawing of the future product. However, often one person draws it up, and another person produces something according to this scheme.
To avoid confusion in understanding the depicted object and its parameters, conventions for length, width, height and other quantities used in design are accepted all over the world. What are they? Let's find out.
Quantities
Area, height and other designations of a similar nature are not only physical, but also mathematical quantities.
Their single letter designation (used by all countries) was established in the mid-twentieth century by the International System of Units (SI) and is still used to this day. It is for this reason that all such parameters are indicated in Latin, and not in Cyrillic letters or Arabic script. In order not to create certain difficulties, when developing standards for design documentation in most modern countries, it was decided to use almost the same conventions that are used in physics or geometry.
Any school graduate remembers that depending on whether a two-dimensional or three-dimensional figure (product) is depicted in the drawing, it has a set of basic parameters. If there are two dimensions, these are width and length, if there are three, height is also added.
So, first, let's find out how to correctly indicate length, width, height in the drawings.
Width
As mentioned above, in mathematics the quantity in question is one of the three spatial dimensions of any object, provided that its measurements are made in the transverse direction. So what is width famous for? It is designated by the letter “B”. This is known all over the world. Moreover, according to GOST, it is permissible to use both capital and lowercase Latin letters. The question often arises as to why this particular letter was chosen. After all, the reduction is usually made according to the first Greek or English name of the quantity. In this case, the width in English will look like “width”.
Probably the point here is that this parameter was initially most widely used in geometry. In this science, when describing figures, length, width, height are often denoted by the letters “a”, “b”, “c”. According to this tradition, when choosing, the letter "B" (or "b") was borrowed from the SI system (although symbols other than geometric ones began to be used for the other two dimensions).
Most believe that this was done so as not to confuse width (designated with the letter "B"/"b") with weight. The fact is that the latter is sometimes referred to as “W” (short for the English name weight), although the use of other letters (“G” and “P”) is also acceptable. According to international standards of the SI system, width is measured in meters or multiples (multiples) of their units. It is worth noting that in geometry it is sometimes also acceptable to use “w” to denote width, but in physics and other exact sciences such a designation is usually not used.
Length
As already indicated, in mathematics, length, height, width are three spatial dimensions. Moreover, if width is a linear dimension in the transverse direction, then length is in the longitudinal direction. Considering it as a quantity of physics, one can understand that this word means a numerical characteristic of the length of lines.
In English this term is called length. It is because of this that this value is denoted by the capital or lowercase initial letter of the word - “L”. Like width, length is measured in meters or their multiples (multiples).
Height
The presence of this value indicates that we have to deal with a more complex - three-dimensional space. Unlike length and width, height numerically characterizes the size of an object in the vertical direction.
In English it is written as "height". Therefore, according to international standards, it is denoted by the Latin letter “H” / “h”. In addition to height, in drawings sometimes this letter also acts as a designation for depth. Height, width and length - all these parameters are measured in meters and their multiples and submultiples (kilometers, centimeters, millimeters, etc.).
Radius and diameter
In addition to the parameters discussed, when drawing up drawings you have to deal with others.
For example, when working with circles, it becomes necessary to determine their radius. This is the name of the segment that connects two points. The first of them is the center. The second is located directly on the circle itself. In Latin this word looks like "radius". Hence the lowercase or capital “R”/“r”.
When drawing circles, in addition to the radius, you often have to deal with a phenomenon close to it - diameter. It is also a line segment connecting two points on a circle. In this case, it necessarily passes through the center.
Numerically, the diameter is equal to two radii. In English this word is written like this: "diameter". Hence the abbreviation - large or small Latin letter “D” / “d”. Often the diameter in the drawings is indicated using a crossed out circle - “Ø”.
Although this is a common abbreviation, it is worth keeping in mind that GOST provides for the use of only the Latin “D” / “d”.
Thickness
Most of us remember school mathematics lessons. Even then, teachers told us that it is customary to use the Latin letter “s” to denote a quantity such as area. However, according to generally accepted standards, a completely different parameter is written in drawings in this way - thickness.
Why is this so? It is known that in the case of height, width, length, the designation by letters could be explained by their writing or tradition. It’s just that thickness in English looks like “thickness”, and in Latin it looks like “crassities”. It is also not clear why, unlike other quantities, thickness can only be indicated in lowercase letters. The notation "s" is also used to describe the thickness of pages, walls, ribs, etc.
Perimeter and area
Unlike all the quantities listed above, the word “perimeter” does not come from Latin or English, but from Greek. It is derived from "περιμετρέο" ("measure the circumference"). And today this term has retained its meaning (the total length of the boundaries of the figure). Subsequently, the word entered the English language (“perimeter”) and was fixed in the SI system in the form of an abbreviation with the letter “P”.
Area is a quantity that shows the quantitative characteristics of a geometric figure that has two dimensions (length and width). Unlike everything listed earlier, it is measured in square meters (as well as in submultiples and multiples thereof). As for the letter designation of the area, it differs in different areas. For example, in mathematics this is the Latin letter “S”, familiar to everyone from childhood. Why this is so - no information.
Some people unknowingly think that this is due to the English spelling of the word "square". However, in it the mathematical area is "area", and "square" is the area in the architectural sense. By the way, it is worth remembering that “square” is the name of the geometric figure “square”. So you should be careful when studying drawings in English. Due to the translation of “area” in some disciplines, the letter “A” is used as a designation. In rare cases, "F" is also used, but in physics this letter stands for a quantity called "force" ("fortis").
Other common abbreviations
The designations for height, width, length, thickness, radius, and diameter are the most commonly used when drawing up drawings. However, there are other quantities that are also often present in them. For example, lowercase "t". In physics, this means “temperature”, however, according to GOST of the Unified System of Design Documentation, this letter is the pitch (of helical springs, etc.). However, it is not used when it comes to gears and threads.
The capital and lowercase letter “A”/“a” (according to the same standards) in the drawings is used to denote not the area, but the center-to-center and center-to-center distance. In addition to different sizes, in drawings it is often necessary to indicate angles of different sizes. For this purpose, it is customary to use lowercase letters of the Greek alphabet. The most commonly used are “α”, “β”, “γ” and “δ”. However, it is acceptable to use others.
What standard defines the letter designation of length, width, height, area and other quantities?
As mentioned above, so that there is no misunderstanding when reading the drawing, representatives of different nations have adopted common standards for letter designation. In other words, if you are in doubt about the interpretation of a particular abbreviation, look at GOSTs. This way you will learn how to correctly indicate height, width, length, diameter, radius, and so on.
It's no secret that there are special notations for quantities in any science. Letter designations in physics prove that this science is no exception in terms of identifying quantities using special symbols. There are quite a lot of basic quantities, as well as their derivatives, each of which has its own symbol. So, letter designations in physics are discussed in detail in this article.
Physics and basic physical quantities
Thanks to Aristotle, the word physics began to be used, since it was he who first used this term, which at that time was considered synonymous with the term philosophy. This is due to the commonality of the object of study - the laws of the Universe, more specifically - how it functions. As you know, the first scientific revolution took place in the 16th-17th centuries, and it was thanks to it that physics was singled out as an independent science.
Mikhail Vasilyevich Lomonosov introduced the word physics into the Russian language by publishing a textbook translated from German - the first physics textbook in Russia.
So, physics is a branch of natural science devoted to the study of the general laws of nature, as well as matter, its movement and structure. There are not as many basic physical quantities as it might seem at first glance - there are only 7 of them:
- length,
- weight,
- time,
- current strength,
- temperature,
- amount of substance
- power of light.
Of course, they have their own letter designations in physics. For example, the symbol chosen for mass is m, and for temperature - T. Also, all quantities have their own unit of measurement: the luminous intensity is candela (cd), and the unit of measurement for the amount of substance is mole.
Derived physical quantities
There are much more derivative physical quantities than basic ones. There are 26 of them, and often some of them are attributed to the main ones.
So, area is a derivative of length, volume is also a derivative of length, speed is a derivative of time, length, and acceleration, in turn, characterizes the rate of change in speed. Momentum is expressed through mass and speed, force is the product of mass and acceleration, mechanical work depends on force and length, energy is proportional to mass. Power, pressure, density, surface density, linear density, amount of heat, voltage, electrical resistance, magnetic flux, moment of inertia, moment of impulse, moment of force - they all depend on mass. Frequency, angular velocity, angular acceleration are inversely proportional to time, and electric charge is directly dependent on time. Angle and solid angle are derived quantities from length.
What letter represents voltage in physics? Voltage, which is a scalar quantity, is denoted by the letter U. For speed, the designation is the letter v, for mechanical work - A, and for energy - E. Electric charge is usually denoted by the letter q, and magnetic flux - F.
SI: general information
The International System of Units (SI) is a system of physical units that is based on the International System of Units, including the names and designations of physical quantities. It was adopted by the General Conference on Weights and Measures. It is this system that regulates letter designations in physics, as well as their dimensions and units of measurement. Letters of the Latin alphabet are used for designation, and in some cases - of the Greek alphabet. It is also possible to use special characters as a designation.
Conclusion
So, in any scientific discipline there are special designations for various kinds of quantities. Naturally, physics is no exception. There are quite a lot of letter symbols: force, area, mass, acceleration, voltage, etc. They have their own symbols. There is a special system called the International System of Units. It is believed that basic units cannot be mathematically derived from others. Derivative quantities are obtained by multiplying and dividing from basic ones.
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The times when current was discovered through the personal sensations of scientists who passed it through themselves are long gone. Now special devices called ammeters are used for this.
An ammeter is a device used to measure current. What is meant by current strength?
Let's look at Figure 21, b. It shows the cross section of the conductor through which charged particles pass when there is an electric current in the conductor. In a metal conductor, these particles are free electrons. As electrons move along a conductor, they carry some charge. The more electrons and the faster they move, the more charge they will transfer in the same time.
Current strength is a physical quantity that shows how much charge passes through the cross section of a conductor in 1 s.
Let, for example, during a time t = 2 s, current carriers carry a charge of q = 4 C through the cross section of the conductor. The charge transferred by them in 1 s will be 2 times less. Dividing 4 C by 2 s, we get 2 C/s. This is the current strength. It is designated by the letter I:
I - current strength.
So, to find the current strength I, it is necessary to divide the electric charge q that passed through the cross section of the conductor in time t by this time:
The unit of current is called ampere (A) in honor of the French scientist A. M. Ampere (1775-1836). The definition of this unit is based on the magnetic effect of current, and we will not dwell on it. If the current strength I is known, then we can find the charge q passing through the cross section of the conductor in time t. To do this, you need to multiply the current by time:
The resulting expression allows us to determine the unit of electric charge - coulomb (C):
1 C = 1 A 1 s = 1 A s.
1 C is the charge that passes through the cross-section of a conductor in 1 s at a current of 1 A.
In addition to the ampere, other (multiple and sub-multiple) units of current strength are often used in practice, for example milliampere (mA) and microampere (µA):
1 mA = 0.001 A, 1 µA = 0.000001 A.
As already mentioned, current is measured using ammeters (as well as milli- and microammeters). The demonstration galvanometer mentioned above is a conventional microammeter.
There are different designs of ammeters. The ammeter, intended for demonstration experiments at school, is shown in Figure 28. The same figure shows its symbol (a circle with the Latin letter “A” inside). 
When connected to a circuit, an ammeter, like any other measuring device, should not have a noticeable effect on the measured value. Therefore, the ammeter is designed in such a way that when it is turned on, the current strength in the circuit remains almost unchanged.
Depending on the purpose, ammeters with different division values are used in technology. The ammeter scale shows what maximum current it is designed for. You cannot connect it to a circuit with a higher current strength, as the device may deteriorate.
To connect the ammeter to the circuit, it is opened and the free ends of the wires are connected to the terminals (clamps) of the device. In this case, the following rules must be observed:
1) the ammeter is connected in series with the circuit element in which the current is measured;
2) the ammeter terminal with the “+” sign should be connected to the wire that comes from the positive pole of the current source, and the terminal with the “–” sign - to the wire that comes from the negative pole of the current source.
When connecting an ammeter to a circuit, it does not matter which side (left or right) of the element being tested it is connected to. This can be verified experimentally (Fig. 29). As you can see, when measuring the current passing through the lamp, both ammeters (the one on the left and the one on the right) show the same value. 
1. What is current strength? What letter does it represent? 2. What is the formula for current strength? 3. What is the unit of current called? How is it designated? 4. What is the name of the device for measuring current? How is it indicated on the diagrams? 5. What rules should be followed when connecting an ammeter to a circuit? 6. What formula is used to find the electric charge passing through the cross section of a conductor if the current strength and the time of its passage are known?
phscs.ru
Basic physical quantities, their letter designations in physics.
It's no secret that there are special notations for quantities in any science. Letter designations in physics prove that this science is no exception in terms of identifying quantities using special symbols. There are quite a lot of basic quantities, as well as their derivatives, each of which has its own symbol. So, letter designations in physics are discussed in detail in this article.
Physics and basic physical quantities
Thanks to Aristotle, the word physics began to be used, since it was he who first used this term, which at that time was considered synonymous with the term philosophy. This is due to the commonality of the object of study - the laws of the Universe, more specifically - how it functions. As you know, the first scientific revolution took place in the 16th-17th centuries, and it was thanks to it that physics was singled out as an independent science.
Mikhail Vasilyevich Lomonosov introduced the word physics into the Russian language by publishing a textbook translated from German - the first physics textbook in Russia.
So, physics is a branch of natural science devoted to the study of the general laws of nature, as well as matter, its movement and structure. There are not as many basic physical quantities as it might seem at first glance - there are only 7 of them:
- length,
- weight,
- time,
- current strength,
- temperature,
- amount of substance
- power of light.
Of course, they have their own letter designations in physics. For example, the symbol chosen for mass is m, and for temperature - T. Also, all quantities have their own unit of measurement: the luminous intensity is candela (cd), and the unit of measurement for the amount of substance is mole.
Derived physical quantities
There are much more derivative physical quantities than basic ones. There are 26 of them, and often some of them are attributed to the main ones.
So, area is a derivative of length, volume is also a derivative of length, speed is a derivative of time, length, and acceleration, in turn, characterizes the rate of change in speed. Momentum is expressed through mass and speed, force is the product of mass and acceleration, mechanical work depends on force and length, energy is proportional to mass. Power, pressure, density, surface density, linear density, amount of heat, voltage, electrical resistance, magnetic flux, moment of inertia, moment of impulse, moment of force - they all depend on mass. Frequency, angular velocity, angular acceleration are inversely proportional to time, and electric charge is directly dependent on time. Angle and solid angle are derived quantities from length.
What letter represents voltage in physics? Voltage, which is a scalar quantity, is denoted by the letter U. For speed, the designation is the letter v, for mechanical work - A, and for energy - E. Electric charge is usually denoted by the letter q, and magnetic flux - F.
SI: general information
The International System of Units (SI) is a system of physical units that is based on the International System of Units, including the names and designations of physical quantities. It was adopted by the General Conference on Weights and Measures. It is this system that regulates letter designations in physics, as well as their dimensions and units of measurement. Letters of the Latin alphabet are used for designation, and in some cases - of the Greek alphabet. It is also possible to use special characters as a designation.
Conclusion
So, in any scientific discipline there are special designations for various kinds of quantities. Naturally, physics is no exception. There are quite a lot of letter symbols: force, area, mass, acceleration, voltage, etc. They have their own symbols. There is a special system called the International System of Units. It is believed that basic units cannot be mathematically derived from others. Derivative quantities are obtained by multiplying and dividing from basic ones.
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| Area (Latin area), vector potential, work (German Arbeit), amplitude (Latin amplitudo), degeneracy parameter, work function (German Austrittsarbeit), Einstein coefficient for spontaneous emission, mass number | |
| Acceleration (lat. acceleratio), amplitude (lat. amplitudo), activity (lat. activitas), thermal diffusivity coefficient, rotational ability, Bohr radius | |
| Magnetic induction vector, baryon number, specific gas constant, virial coefficient, Brillouin function, interference fringe width (German Breite), brightness, Kerr constant, Einstein coefficient for stimulated emission, coefficient Einstein for absorption, rotational constant of the molecule | |
| Magnetic induction vector, beauty/bottom quark, Wien constant, width (German: Breite) | |
| electric capacity (eng. capacitance), heat capacity (eng. heatcapacity), constant of integration (lat. constans), charm (eng. charm), Clebsch-Gordan coefficients (eng. Clebsch-Gordan coefficients), Cotton-Mouton constant (eng. Cotton-Mouton constant), curvature (lat. curvatura) | |
| Speed of light (Latin celeritas), speed of sound (Latin celeritas), heat capacity, magic quark, concentration, first radiation constant, second radiation constant | |
| Electric displacement field vector, diffusion coefficient, dioptric power, transmission coefficient, quadrupole electric moment tensor, angular dispersion of a spectral device, linear dispersion of a spectral device, potential transparency coefficient barrier, de-plus meson (English Dmeson), de-zero meson (English Dmeson), diameter (Latin diametros, ancient Greek διάμετρος) | |
| Distance (Latin distantia), diameter (Latin diametros, Ancient Greek διάμετρος), differential (Latin differentia), down quark, dipole moment, diffraction grating period, thickness (German: Dicke) | |
| Energy (Latin energīa), electric field strength (English electric field), electromotive force (English electromotive force), magnetomotive force, illumination (French éclairement lumineux), emissivity of the body, Young's modulus | |
| 2.71828…, electron, elementary electric charge, electromagnetic interaction constant | |
| Force (lat. fortis), Faraday constant, Helmholtz free energy (German freie Energie), atomic scattering factor, electromagnetic field strength tensor, magnetomotive force, shear modulus | |
| Frequency (lat. frequentia), function (lat. functia), volatility (ger. Flüchtigkeit), force (lat. fortis), focal length (eng. focal length), oscillator strength, friction coefficient | |
| Gravitational constant, Einstein tensor, Gibbs free energy, space-time metric, virial, partial molar value, adsorbate surface activity, shear modulus, total field momentum, gluon ), Fermi constant, conductivity quantum, electrical conductivity, weight (German: Gewichtskraft) | |
| Gravitational acceleration, gluon, Lande factor, degeneracy factor, weight concentration, graviton, constant Gauge interactions | |
| Magnetic field strength, equivalent dose, enthalpy (heat contents or from the Greek letter “eta”, H - ενθαλπος), Hamiltonian, Hankel function, Heaviside step function ), Higgs boson, exposure, Hermite polynomials | |
| Height (German: Höhe), Planck's constant (German: Hilfsgröße), helicity (English: helicity) | |
| current intensity (French intensité de courant), sound intensity (Latin intēnsiō), light intensity (Latin intēnsiō), radiation intensity, luminous intensity, moment of inertia, magnetization vector | |
| Imaginary unit (lat. imaginarius), unit vector | |
| Current density, angular momentum, Bessel function, moment of inertia, polar moment of inertia of the section, internal quantum number, rotational quantum number, luminous intensity, J/ψ meson | |
| Imaginary unit, current density, unit vector, internal quantum number, 4-vector current density | |
| Kaons (eng. kaons), thermodynamic equilibrium constant, coefficient of electronic thermal conductivity of metals, modulus of uniform compression, mechanical impulse, Josephson constant | |
| Coefficient (German: Koeffizient), Boltzmann constant, thermal conductivity, wave number, unit vector | |
| Momentum, inductance, Lagrangian function, classical Langevin function, Lorenz number, sound pressure level, Laguerre polynomials, orbital quantum number, energy brightness, brightness (eng. luminance) | |
| Length, mean free path, orbital quantum number, radiation length | |
| Moment of force, magnetization vector, torque, Mach number, mutual inductance, magnetic quantum number, molar mass | |
| Mass (lat. massa), magnetic quantum number (eng. magnetic quantum number), magnetic moment (eng. magnetic moment), effective mass, mass defect, Planck mass | |
| Quantity (lat. numerus), Avogadro's constant, Debye number, total radiation power, optical instrument magnification, concentration, power | |
| Refractive index, amount of matter, normal vector, unit vector, neutron, quantity, fundamental quantum number, rotation frequency, concentration, polytropic index, Loschmidt constant | |
| Origin of coordinates (lat. origo) | |
| Power (lat. potestas), pressure (lat. pressūra), Legendre polynomials, weight (fr. poids), gravity, probability (lat. probabilitas), polarizability, transition probability, 4-momentum | |
| Momentum (lat. petere), proton (eng. proton), dipole moment, wave parameter | |
| Electric charge (English quantity of electricity), quantity of heat (English quantity of heat), generalized force, radiation energy, light energy, quality factor (English quality factor), zero Abbe invariant, quadrupole electric moment (English quadrupole moment) , nuclear reaction energy | |
| Electric charge, generalized coordinate, quantity of heat, effective charge, quality factor | |
| Electrical resistance, gas constant, Rydberg constant, von Klitzing constant, reflectance, resistance, resolution, luminosity, particle path, distance | |
| Radius (lat. radius), radius vector, radial polar coordinate, specific heat of phase transition, specific heat of fusion, specific refraction (lat. rēfractiō), distance | |
| Surface area, entropy, action, spin, spin quantum number, strangeness, Hamilton's principal function, scattering matrix , evolution operator, Poynting vector | |
| Displacement (Italian ь s "postamento), strange quark (English strange quark), path, space-time interval (English spacetime interval), optical path length | |
| Temperature (lat. temperātūra), period (lat. tempus), kinetic energy, critical temperature, therm, half-life, critical energy, isospin | |
| Time (Latin tempus), true quark, truthfulness, Planck time | |
| Internal energy, potential energy, Umov vector, Lennard-Jones potential, Morse potential, 4-speed, electrical voltage | |
| Up quark, speed, mobility, specific internal energy, group velocity | |
| Volume (French volume), voltage (English voltage), potential energy, visibility of the interference fringe, Verdet constant (English Verdet constant) | |
| Velocity (lat. vēlōcitās), phase velocity, specific volume | |
| Mechanical work, work function, W boson, energy, binding energy of the atomic nucleus, power | |
| Speed, energy density, internal conversion ratio, acceleration | |
| Reactance, longitudinal increase | |
| Variable, displacement, Cartesian coordinate, molar concentration, anharmonicity constant, distance | |
| Hypercharge, force function, linear increase, spherical functions | |
| Cartesian coordinate | |
| Impedance, Z boson, atomic number or nuclear charge number (German: Ordnungszahl), partition function (German: Zustandssumme), Hertz vector, valence, electrical impedance, angular magnification, characteristic vacuum impedance | |
| Cartesian coordinate | |
| Thermal expansion coefficient, alpha particles, angle, fine structure constant, angular acceleration, Dirac matrices, expansion coefficient, polarization, heat transfer coefficient, dissociation coefficient, specific thermoelectromotive force, Mach angle, absorption coefficient, natural indicator of light absorption, degree of emissivity of the body, damping constant | |
| Angle, beta particles, particle speed divided by the speed of light, quasi-elastic force coefficient, Dirac matrices, isothermal compressibility, adiabatic compressibility, damping coefficient, angular width of interference fringes, angular acceleration | |
| Gamma function, Christophel symbols, phase space, adsorption magnitude, velocity circulation, energy level width | |
| Angle, Lorentz factor, photon, gamma rays, specific gravity, Pauli matrices, gyromagnetic ratio, thermodynamic pressure coefficient, surface ionization coefficient, Dirac matrices, adiabatic exponent | |
| Variation of magnitude (eg), Laplace operator, dispersion, fluctuation, degree of linear polarization, quantum defect | |
| Small displacement, Dirac delta function, Kronecker delta | |
| Electrical constant, angular acceleration, unit antisymmetric tensor, energy | |
| Riemann zeta function | |
| Efficiency, dynamic viscosity coefficient, metric Minkowski tensor, internal friction coefficient, viscosity, scattering phase, eta meson | |
| Statistical temperature, Curie point, thermodynamic temperature, moment of inertia, Heaviside function | |
| Angle to the X axis in the XY plane in spherical and cylindrical coordinate systems, potential temperature, Debye temperature, nutation angle, normal coordinate, wetting measure, Cubbibo angle, Weinberg angle | |
| Extinction coefficient, adiabatic index, magnetic susceptibility of the medium, paramagnetic susceptibility | |
| Cosmological constant, Baryon, Legendre operator, lambda hyperon, lambda plus hyperon | |
| Wavelength, specific heat of fusion, linear density, mean free path, Compton wavelength, operator eigenvalue, Gell-Mann matrices | |
| Friction coefficient, dynamic viscosity, magnetic permeability, magnetic constant, chemical potential, Bohr magneton, muon, erected mass, molar mass, Poisson's ratio, nuclear magneton | |
| Frequency, neutrino, kinematic viscosity coefficient, stoichiometric coefficient, amount of matter, Larmor frequency, vibrational quantum number | |
| Grand canonical ensemble, xi-null-hyperon, xi-minus-hyperon | |
| Coherence length, Darcy coefficient | |
| Product, Peltier coefficient, Poynting vector | |
| 3.14159…, pi-bond, pi-plus meson, pi-zero meson | |
| Resistivity, density, charge density, radius in polar coordinate system, spherical and cylindrical coordinate systems, density matrix, probability density | |
| Summation operator, sigma-plus-hyperon, sigma-zero-hyperon, sigma-minus-hyperon | |
| Electrical conductivity, mechanical stress (measured in Pa), Stefan-Boltzmann constant, surface density, reaction cross section, sigma coupling, sector velocity, surface tension coefficient, specific photoconductivity, differential scattering cross section, screening constant, thickness | |
| Lifetime, tau lepton, time interval, lifetime, period, linear charge density, Thomson coefficient, coherence time, Pauli matrix, tangential vector | |
| Y boson | |
| Magnetic flux, electric displacement flux, work function, ide, Rayleigh dissipative function, Gibbs free energy, wave energy flux, lens optical power, radiation flux, luminous flux, magnetic flux quantum | |
| Angle, electrostatic potential, phase, wave function, angle, gravitational potential, function, Golden ratio, mass force field potential | |
| X boson | |
| Rabi frequency, thermal diffusivity, dielectric susceptibility, spin wave function | |
| Wave function, interference aperture | |
| Wave function, function, current function | |
| Ohm, solid angle, number of possible states of a statistical system, omega-minus-hyperon, angular velocity of precession, molecular refraction, cyclic frequency | |
| Angular frequency, meson, state probability, Larmor frequency of precession, Bohr frequency, solid angle, flow velocity |
dik.academic.ru
| Magnitude | Designation | SI unit of measurement | |
| Current strength | I | ampere | A |
| Current Density | j | ampere per square meter | A/m2 |
| Electric charge | Q, q | pendant | Cl |
| Electric dipole moment | p | coulomb meter | Cl ∙ m |
| Polarization | P | pendant per square meter | C/m2 |
| Voltage, potential, EMF | U, φ, ε | volt | IN |
| Electric field strength | E | volt per meter | V/m |
| Electrical capacity | C | farad | F |
| Electrical resistance | R, r | ohm | Ohm |
| Electrical resistivity | ρ | ohm meter | Ohm ∙ m |
| Electrical conductivity | G | Siemens | Cm |
| Magnetic induction | B | tesla | Tl |
| Magnetic flux | F | weber | Wb |
| Magnetic field strength | H | ampere per meter | Vehicle |
| Magnetic moment | pm | ampere square meter | A ∙ m2 |
| Magnetization | J | ampere per meter | Vehicle |
| Inductance | L | Henry | Gn |
| Electromagnetic energy | N | joule | J |
| Volumetric energy density | w | joule per cubic meter | J/m3 |
| Active power | P | watt | W |
| Reactive power | Q | var | var |
| Full power | S | watt-ampere | W∙A |
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Physical quantities of electric current
Hello, dear readers of our site! We continue the series of articles dedicated to novice electricians. Today we will briefly look at the physical quantities of electric current, types of connections and Ohm's law.
First, let's remember what types of current exist:
Alternating current (letter designation AC) - is generated due to the magnetic effect. This is the same current that you and I have in our homes. It does not have any poles because it changes them many times per second. This phenomenon (change of polarities) is called frequency, it is expressed in hertz (Hz). Currently, our network uses an alternating current of 50 Hz (that is, a change in direction occurs 50 times per second). The two wires that enter the home are called phase and neutral, since there are no poles.
Direct current (letter designation DC) is the current that is obtained chemically (for example, batteries, accumulators). It is polarized and flows in a certain direction.
Basic physical quantities:
- Potential difference (symbol U). Since generators act on electrons like a water pump, there is a difference across its terminals, which is called a potential difference. It is expressed in volts (designation B). If you and I measure the potential difference at the input and output connections of an electrical appliance with a voltmeter, we will see a reading of 230-240 V. Usually this value is called voltage.
- Current strength (designation I). Let's say when a lamp is connected to a generator, an electrical circuit is created that passes through the lamp. A stream of electrons flows through the wires and through the lamp. The strength of this current is expressed in amperes (symbol A).
- Resistance (designation R). Resistance usually refers to the material that allows electrical energy to be converted into heat. Resistance is expressed in ohms (symbol Ohm). Here we can add the following: if the resistance increases, then the current decreases, since the voltage remains constant, and vice versa, if the resistance decreases, the current increases.
- Power (designation P). Expressed in watts (symbol W), it determines the amount of energy consumed by the appliance that is currently connected to your outlet.
Types of consumer connections
Conductors, when included in a circuit, can be connected to each other in various ways:
- Consistently.
- Parallel.
- Mixed method
A serial connection is a connection in which the end of the previous conductor is connected to the beginning of the next one.
A parallel connection is a connection in which all the beginnings of the conductors are connected at one point, and the ends at another.
A mixed connection of conductors is a combination of series and parallel connections. Everything we have told in this article is based on the basic law of electrical engineering - Ohm's law, which states that the current strength in a conductor is directly proportional to the applied voltage at its ends and inversely proportional to the resistance of the conductor.
In the form of a formula, this law is expressed as follows:
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