Systems of units SI and CGS. Some units of measurement

The table shows the names symbols and the dimensions of the most commonly used units in the SI system. To transition to other systems - SGSE and SGSM - the last columns show the relationships between the units of these systems and the corresponding units of the SI system.

For mechanical quantities, the SGSE and SGSM systems are completely identical; the main units here are the centimeter, gram and second.

The difference in GHS systems occurs for electrical quantities. This is due to the fact that the GSSE adopted as the fourth basic unit electrical permeability voids (ε 0 =1), and in SGSM - magnetic permeability of voids (μ 0 =1).

In the Gaussian system, the basic units are centimeter, gram and second, ε 0 =1 and μ 0 =1 (for vacuum). In this system, electrical quantities are measured in SGSE, magnetic quantities - in SGSM.

Magnitude	Name	Dimension	Designation	Contains units GHS systems
Magnitude	Name	Dimension	Designation	SSSE	SGSM
Basic units
Length	meter	m	m	10 2 cm
Weight	kilogram	kg	kg	10 3 g
Time	second	sec	sec	1sec
Current strength	ampere	A	A	3×10 9	10 -1
Temperature	Kelvin	TO	TO	-	-
Temperature	degrees Celsius	°C	°C	-	-
The power of light	candela	cd	cd	-	-
Mechanical units
Quantity electricity	pendant		Cl	3×10 9	10 -1
Voltage, EMF	volt		IN		10 8
Tension electric field	volt per meter				10 8
Electrical capacity	farad		F	9×10 11 cm	10 -9
Electrical resistance	ohm		Ohm		10 9
Specific resistance	ohm meter				10 11
Dielectric permeability	farad per meter
Magnetic units
Tension magnetic field	ampere per meter
Magnetic induction	tesla		Tl		10 4 Gs
Magnetic flux	weber		Wb		10 8 Mks
Inductance	Henry		Gn		10 8 cm
Magnetic permeability	henry per meter
Optical units
Solid angle	steradian	erased	erased	-	-
Light flow	lumen		lm	-	-
Brightness	nit		nt	-	-
Illumination	luxury		OK	-	-

Some definitions

Force electric current - the strength of an unchanging current, which, passing through two parallel straight conductors of infinite length and negligible cross-section, located at a distance of 1 m from each other in a vacuum, would cause between these conductors a force equal to 2 × 10 -7 N per meter of length.
Kelvin- unit of temperature measurement equal to 1/273 of the interval from absolute zero temperatures up to the melting temperature of ice.
Candela(candle) - the intensity of light emitted from an area of 1/600000 m 2 of the cross section of the full emitter, in the direction perpendicular to this section, at the temperature of the emitter, equal temperature solidification of platinum at a pressure of 1011325 Pa.
Newton- a force that imparts an acceleration of 1 m/s 2 to a body weighing 1 kg in the direction of its action.
Pascal- pressure caused by a force of 1 N, uniformly distributed over a surface area of 1 m 2.
Joule- the work done by a force of 1N when it moves a body at a distance of 1m in the direction of its action.
Watt- power at which work equal to 1 J is performed in 1 second.
Pendant- the amount of electricity passing through cross section conductor for 1 second at a current of 1A.
Volt- voltage in a section of an electrical circuit with a direct current of 1A, in which 1W of power is expended.
Volts per meter- the intensity of a uniform electric field, at which a potential difference of 1V is created between points located at a distance of 1 m along the field strength line.
Ohm- the resistance of the conductor, between the ends of which a voltage of 1V arises at a current of 1A.
Ohm meter- electrical resistance of the conductor at which the cylindrical straight conductor a cross-sectional area of 1 m2 and a length of 1 m has a resistance of 1 Ohm.
Farad- the capacitance of a capacitor, between the plates of which a voltage of 1V arises when charged at 1 C.
Ampere per meter- magnetic field strength at the center long solenoid with n turns for each meter of length through which a current of strength A/n passes.
Weber- magnetic flux, when it decreases to zero, an amount of electricity of 1 C passes through a circuit connected to this flux with a resistance of 1 Ohm.
Henry- inductance of the circuit, with which, under force direct current in it 1A a magnetic flux of 1Wb is coupled.
Tesla- magnetic induction, at which the magnetic flux through a cross section with an area of 1 m 2 is equal to 1 Wb.
Henry per meter- absolute magnetic permeability of the medium in which, at a magnetic field strength of 1A/m, a magnetic induction of 1H is created.
Steradian- a solid angle, the vertex of which is located at the center of the sphere and which cuts out an area on the surface of the sphere, equal to the area square with side equal to the radius spheres.
Lumen- product of the luminous intensity of the source and the solid angle into which the luminous flux is sent.

Some off-system units

Magnitude	Unit		Value in SI units
Magnitude	Name	designation	Value in SI units
Force	kilogram-wall force	sn	10N
Pressure and mechanical voltage	technical atmosphere	at	98066.5Pa
	kilogram-force per square centimeter	kgf/cm 2	98066.5Pa
	physical atmosphere	atm	101325Pa
	millimeter of water column	mm water Art.	9.80665Pa
	millimeter of mercury	mmHg Art.	133.322Pa
Work and Energy	kilogram-force meter	kgf×m	9.80665J
Work and Energy	kilowatt-hour	kWh	3.6×10 6 J
Power	kilogram-force meter per second	kgf×m/s	9.80665W
Power	Horsepower	hp	735.499W

Interesting fact. The concept of horsepower was introduced by my father. famous physicist Watt. Watt's father was a steam engine designer, and it was vital for him to convince mine owners to buy his machines instead of draft horses. So that mine owners could calculate the benefits, Watt coined the term horsepower to define the power of steam engines. One HP according to Watt, this is 500 pounds of load that a horse could pull all day long. So one horsepower is the ability to pull a cart with 227 kg of cargo during a 12-hour working day. The steam engines sold by Watt had only a few horsepower.

Prefixes and factors to form decimal multiples and submultiple units

Console	Designation		The multiplier by which units are multiplied SI systems
Console	domestic	international
Mega	M	M	10 6
Kilo	To	k	10 3
Hecto	G	h	10 2
Deca	Yes	da	10
Deci	d	d	10 -1
Santi	With	c	10 -2
Milli	m	m	10 -3
Micro	mk	µ	10 -6
Nano	n	n	10 -9
Pico	P	p	10 -12

There are a number of additional units dimensions that are derived from the main ones. Some physical constants turn out to be dimensionless. There are several variants of the GHS, differing in the choice of electrical and magnetic units of measurement and the magnitude of the constants in various laws electromagnetism (SGSE, SGSM, Gaussian system of units).

GHS differs from SI not only in the choice of specific units of measurement. Due to the fact that the SI additionally introduced basic units for electromagnetic physical quantities, which were not in the GHS, some units have other dimensions. Because of this, some physical laws in these systems they are written differently (for example, Coulomb's law). The difference lies in the coefficients, most of which are dimensional. Therefore, if you simply substitute SI units into the formulas written in the GHS, incorrect results will be obtained. The same applies to different types of SGS - in SGSE, SGSM and the Gaussian system of units, the same formulas can be written differently.

The SGS formulas do not contain the non-physical coefficients required in the SI (for example, the electric constant in Coulomb's law), therefore it is considered more convenient for theoretical studies.

IN scientific works As a rule, the choice of one system or another is determined more by the continuity of designations rather than by convenience.

GHS extensions

To facilitate work in the SGS in electrodynamics, the additional systems SGSM and SGSE were adopted.

SGSM

SSSE

In SGSE µ 0 = 1/ With 2 (dimension: s 2 / cm 2), ε 0 = 1. Electrical units in the SGSE system are used mainly in theoretical works. They do not have their own names and are inconvenient for measurements.

SGS symmetrical, or Gaussian system of units

In a symmetrical SGS (also called a mixed SGS or Gaussian system of units), magnetic units are equal to the units of the GSMS system, electrical units are equal to the units of the GSSE system. The magnetic and electric constants in this system are unit and dimensionless: µ 0 = 1, ε 0 = 1.

Story

A system of measures based on the centimeter, gram and second was proposed by the German scientist Gauss in . Maxwell and Thomson improved the system by adding electromagnetic units of measurement.

The values of many units of the GHS system were found to be inconvenient for practical use, and it was soon replaced by a system based on the meter, kilogram and second (ISS). The GHS continued to be used in parallel with the ISS, mainly in scientific research.

Of the three additional systems The most widely used system is the SGS symmetrical system.

Some units of measurement

speed - cm/s;
acceleration - cm/s²;
force - dyne, g cm/s²;
energy - erg, g cm²/s²;
power - erg/s, g cm²/s³;
pressure - dyne/cm², g/(cm·s²);
dynamic viscosity - poise, g/(cm s);
kinematic viscosity - Stokes, cm²/s;
magnetomotive force - Hilbert.

More about electric charge

General information

Surprisingly, we encounter static electricity every day - when we pet our beloved cat, comb our hair, or pull on a synthetic sweater. So we ourselves inevitably become generators of static electricity. We literally bathe in it, because we live in the strong electrostatic field of the Earth. This field arises due to the fact that it is surrounded by the ionosphere, upper layer atmosphere is an electrically conductive layer. The ionosphere was formed under the influence cosmic radiation and has its own charge. While doing everyday things like heating food, we don’t think at all about the fact that we are using static electricity when we turn on the gas supply valve on a burner with automatic ignition or bring an electric lighter to it.

Examples of static electricity

Since childhood, we have been instinctively afraid of thunder, although in itself it is absolutely safe - just an acoustic consequence of a menacing lightning strike, which is caused by atmospheric static electricity. Sailors of the times sailing fleet fell into sacred awe, observing the lights of St. Elmo on their masts, which are also a manifestation of atmospheric static electricity. People endowed supreme gods ancient religions an integral attribute in the form of lightning, be it the Greek Zeus, the Roman Jupiter, the Scandinavian Thor or the Russian Perun.

Centuries have passed since people first began to be interested in electricity, and sometimes we do not even suspect that scientists, having drawn thoughtful conclusions from the study of static electricity, are saving us from the horrors of fires and explosions. We've tamed electrostatics by pointing lightning rods at the sky and equipping fuel tankers with grounding devices that allow electrostatic charges to escape safely into the ground. And, nevertheless, static electricity continues to misbehave, interfering with the reception of radio signals - after all, up to 2000 thunderstorms are raging on Earth at the same time, which generate up to 50 lightning strikes every second.

People have been studying static electricity since time immemorial; We even owe the term “electron” to the ancient Greeks, although they meant something slightly different by this - that’s what they called amber, which was perfectly electrified by friction (other - Greek ἤλεκτρον - amber). Unfortunately, the science of static electricity was not without casualties - Russian scientist Georg Wilhelm Richmann was killed by a lightning bolt during an experiment, which is the most dangerous manifestation of atmospheric static electricity.

Static electricity and weather

To a first approximation, the mechanism of formation of charges in a thundercloud is in many ways similar to the mechanism of electrification of a comb - electrification by friction occurs in the same way. Ice floes, formed from small droplets of water, cooled due to transport by rising air currents to the upper, colder part of the cloud, collide with each other. Larger pieces of ice are charged negatively, and smaller pieces are charged positively. Due to the difference in weight, a redistribution of ice floes in the cloud occurs: large, heavier floes fall to the lower part of the cloud, and lighter, smaller floes gather at the top of the thundercloud. Although the cloud as a whole remains neutral, Bottom part clouds gets negative charge, and the top one is positive.

Just as an electrified comb attracts a balloon due to the induction of an opposite charge on the side closest to the comb, a thundercloud induces on the surface of the Earth positive charge. As the thundercloud develops, the charges increase, and the field strength between them increases, and when the field strength exceeds critical value for data weather conditions, an electrical breakdown of the air occurs - a lightning discharge.

Humanity is indebted to Benjamin Franklin - later President of the Supreme Executive Council of Pennsylvania and the first Postmaster General of the United States - for the invention of the lightning rod (it would be more accurate to call it a lightning rod), which forever saved the world's population from fires caused by lightning striking buildings. By the way, Franklin did not patent his invention, making it available to all mankind.

Lightning did not always cause only destruction - the Ural ore miners determined the location of iron and copper ores precisely by the frequency of lightning strikes at certain points in the area.

Among the scientists who devoted their time to studying the phenomena of electrostatics, it is necessary to mention the Englishman Michael Faraday, later one of the founders of electrodynamics, and the Dutchman Pieter van Muschenbrouck, the inventor of the prototype of the electric capacitor - the famous Leyden jar.

Watching DTM, IndyCar or Formula 1 races, we don’t even suspect that mechanics call pilots to change tires to rain tires, relying on weather radar data. And these data, in turn, are based precisely on electrical characteristics approaching thunderclouds.

Static electricity is our friend and enemy at the same time: radio engineers do not like it, pulling grounding bracelets when repairing burnt circuit boards as a result of a nearby lightning strike - in this case, as a rule, the input stages of the equipment fail. If the grounding equipment is faulty, it can cause severe man-made disasters with tragic consequences - fires and explosions of entire factories.

Static electricity in medicine

However, it comes to the aid of people with heart rhythm disturbances caused by chaotic convulsive contractions of the patient’s heart. Its normal operation is restored by passing a small electrostatic discharge using a device called a defibrillator. The scene of a patient returning from the dead with the help of a defibrillator is a kind of classic for a certain genre of cinema. It should be noted that movies traditionally show a monitor with a missing heartbeat signal and an ominous straight line, when in fact using a defibrillator does not help if the patient's heart has stopped.

Other examples

It would be useful to remember the need to metallize aircraft to protect against static electricity, that is, to connect all metal parts of the aircraft, including the engine, into one electrically integral structure. Static dischargers are installed at the tips of the entire tail of the aircraft to drain static electricity that accumulates during flight due to air friction against the aircraft body. These measures are necessary to protect against interference caused by static electricity and to ensure reliable operation of the avionics equipment.

Electrostatics plays a certain role in introducing students to the section “Electricity” - perhaps none of the sections of physics knows more spectacular experiments - here you have hair standing on end and a chase balloon behind the comb, and the mysterious glow of fluorescent lamps without any connection of wires! But this glow effect of gas-filled devices saves the lives of electricians dealing with high voltage in modern power lines and distribution networks.

And most importantly, scientists came to the conclusion that static electricity, or rather to its discharges in the form of lightning, we probably owe the appearance of life on Earth. During experiments in the middle of the last century, with transmission electrical discharges through a mixture of gases similar in composition to primary staff atmosphere of the Earth, one of the amino acids was obtained, which is the “building block” of our life.

To tame electrostatics, it is very important to know the potential difference or electrical voltage, for the measurement of which instruments called voltmeters were invented. The concept of electrical voltage was introduced by the 19th century Italian scientist Alessandro Volta, after whom this unit is named. At one time, galvanometers named after Volta's compatriot Luigi Galvani were used to measure electrostatic voltage. Unfortunately, these electrodynamic type devices introduced distortions into the measurements.

Study of static electricity

Scientists began systematically studying the nature of electrostatics since the work of the 18th century French scientist Charles Augustin de Coulomb. In particular, he introduced the concept of electric charge and discovered the law of interaction of charges. The unit of measurement of the amount of electricity - the coulomb (C) - is named after him. True, for the sake of historical justice, it should be noted that years earlier the English scientist Lord Henry Cavendish was engaged in this; Unfortunately, he wrote on the table and his works were published by his heirs only 100 years later.

Works of predecessors devoted to laws electrical interactions, enabled physicists George Green, Carl Friedrich Gauss and Simeon Denis Poisson to create a mathematically elegant theory that we still use today. The main principle in electrostatics is the electron postulate - elementary particle, which is part of any atom and is easily separated from it under the influence external forces. In addition, there are postulates about the repulsion of like charges and the attraction of unlike charges.

Electricity measurement

One of the first measuring instruments was the simplest electroscope, invented by the English priest and physicist Abraham Bennett - two sheets of gold electrically conductive foil placed in a glass container. Since then measuring instruments have evolved significantly - and now they can measure differences in nanocoulomb units. Using particularly precise physical instruments, Russian scientist Abram Ioffe and American physicist Robert Andrews Millikan was able to measure the electric charge of an electron

Nowadays, with the development digital technologies, ultra-sensitive and high-precision devices with unique characteristics, which, due to the high input impedance, introduce almost no distortion into the measurements. In addition to measuring voltage, such devices allow you to measure other important characteristics electrical circuits, such as ohmic resistance and flowing current over a wide measurement range. The most advanced devices, called multimeters because of their versatility, or, in jargon, testers, also allow you to measure frequency alternating current, capacitance of capacitors and test transistors and even measure temperature.

As a rule, modern devices have built-in protection that does not allow the device to be damaged if misuse. They are compact, easy to handle and absolutely safe to use - each of them goes through a series of accuracy tests, is tested under severe operating conditions and deservedly receives a safety certificate.

Do you find it difficult to translate units of measurement from one language to another? Colleagues are ready to help you. Post a question in TCTerms and within a few minutes you will receive an answer.

Calculations for converting units in the converter " Electric charge converter" are performed using unitconversion.org functions.

Before the introduction of the international system of SI units, the following systems of units were used.

Metric system measures- a set of units of physical quantities, which is based on two units: the meter is a unit of length, the kilogram is a unit of mass. Distinctive feature The metric system of measures was based on the principle of decimal ratios in relation to multiples and submultiples. Metric system, introduced initially in France, received in the second half of the 19th century. international recognition.

Gauss system.

For the first time the concept of a system of units of physical quantities was introduced German mathematician K. Gauss (1832). Gauss's idea was as follows. First, several quantities are selected that are independent of each other. These quantities are called basic, and their units are called basic units. systems of units. Basic quantities are chosen so that, using formulas expressing the relationship between physical quantities, it is possible to form units of other quantities. Gauss called units obtained using formulas and expressed in terms of basic units derived units. Using his idea, Gauss built system of units magnetic quantities. The main units of this Gaussian system were chosen: millimeter - a unit of length, second - a unit of time. Gauss's ideas turned out to be very fruitful. All subsequent systems of units were built on the principles he proposed.

GHS system

GHS system built on the basis of the LMT system of quantities. The basic units of the CGS system: centimeter - a unit of length, gram - a unit of mass, second - a unit of time. In the GHS system, using the indicated three basic units, derived units of mechanical and acoustic quantities are established. Using the unit of thermodynamic temperature - the kelvin - and the unit of luminous intensity - the candela - the GHS system extends to the field of thermal and optical quantities.

ISS system.

Basic units ISS systems: meter is a unit of length, kilogram is a unit of mass, second is a unit of time. Just like the SGS system, the ISS system is built on the basis of the LMT system of quantities. This system of units was proposed in 1901 by the Italian engineer Giorgi and contained, in addition to the basic ones, derived units of mechanical and acoustic quantities. By adding thermodynamic temperature, the kelvin, and luminous intensity, the candela, as basic units, the ISS system could be extended to the realm of thermal and luminous quantities.

MTS system.

MTS unit system built on the basis of the LMT system of quantities. The basic units of the system: meter - a unit of length, ton - a unit of mass, second - a unit of time. The MTS system was developed in France and legalized by its government in 1919. The MTS system was adopted in the USSR and in accordance with state standard was used for more than 20 years (1933 - 1955). The unit of mass of this system - the ton - in its size turned out to be convenient in a number of industries dealing with relatively large masses. The MTS system also had a number of other advantages. Firstly, the numerical values of the density of matter when expressed in the MTS system coincided with numerical values this value when expressed in the SGS system (for example, in the SGS system the density of iron is 7.8 g/cm3, in the MTS system - 7.8 t/m3). Secondly, the unit of work of the MTS system - kilojoule - had a simple relationship with the unit of work of the ISS system (1 kJ = 1000 J). But the sizes of the units of the vast majority of derived quantities in this system turned out to be inconvenient in practice. In the USSR, the MTS system was abolished in 1955.

MKGSS system.

MKGSS unit system built on the basis of the LFT system of quantities. Its basic units are: meter - a unit of length, kilogram-force - a unit of force, second - a unit of time. Kilogram-force is a force equal to the weight of a body weighing 1 kg at normal acceleration free fall g0 = 9.80665 m/s2. This unit of force, as well as some derived units of the MKGSS system, turned out to be convenient when used in technology. Therefore the system received wide use in mechanics, heat engineering and a number of other industries. The main disadvantage of the MKGSS system is its very limited possibilities of application in physics. A significant disadvantage of the MKGSS system is also that the unit of mass in this system does not have a simple decimal relationship with the units of mass of other systems. With introduction International system units, the MKGSS system has lost its meaning.

Systems of units of electromagnetic quantities. There are two known ways to construct systems of electrical and magnetic quantities based on the GHS system: on three basic units (centimeter, gram, second) and on four basic units (centimeter, gram, second and one unit of electrical or magnetic quantity). In the first way, that is, using three basic units based on the SGS system, three systems of units were obtained: electrostatic system of units (SGSE system), electromagnetic system of units (SGSM system), symmetrical system of units (SGS system). Let's consider these systems.

SGSE system

Electrostatic system of units (SGSE system). In constructing this system, the first derivative of the electrical unit is the unit of electric charge using Coulomb's law as the governing equation. At the same time, absolute the dielectric constant is considered a dimensionless electrical quantity. As a consequence of this, in some equations relating electromagnetic quantities, the square root of the speed of light in vacuum appears explicitly.

SGSM system

Electromagnetic system of units (SGSM system). In constructing this system, the first derivative of the electrical unit is the unit of current, using Ampere's law as the governing equation. In this case, absolute magnetic permeability is considered a dimensionless electrical quantity. In this regard, in some equations relating electromagnetic quantities, the square root of the speed of light in vacuum appears explicitly.

GHS system

Symmetrical system of units (SGS system). This system is a combination of the SGSE and SGSM systems. In the SGS system, units of the SGSE system are used as units of electrical quantities, and units of the SGSM system are used as units of magnetic quantities. As a result of the combination of the two systems, in some equations connecting electrical and magnetic quantities, the square root of the speed of light in vacuum appears explicitly.

CGS (centimeter-gram-second)- a system of units of measurement that was widely used before the adoption of the International System of Units (SI). Another name is absolute physical system units.

Within the framework of the GHS, there are three independent dimensions (length, mass and time), all others are reduced to them by multiplication, division and exponentiation (possibly fractional). In addition to the three basic units of measurement - centimeter, gram and second, in the GHS there are a number of additional units of measurement that are derived from the basic ones. Some physical constants turn out to be dimensionless. There are several variants of the SGS, differing in the choice of electrical and magnetic units of measurement and the magnitude of the constants in the various laws of electromagnetism (SGSE, SGSM, Gaussian system of units). GHS differs from SI not only in the choice of specific units of measurement. Due to the fact that the SI additionally introduced basic units for electromagnetic physical quantities that were not in the GHS, some units have different dimensions. Because of this, some physical laws in these systems are written differently (for example, Coulomb's law). The difference lies in the coefficients, most of which are dimensional. Therefore, if you simply substitute SI units into the formulas written in the GHS, incorrect results will be obtained. The same applies to different types of SGS - in SGSE, SGSM and the Gaussian system of units, the same formulas can be written differently.

The GHS formulas lack the non-physical coefficients required in SI (for example, the electric constant in Coulomb's law), and, in the Gaussian variety, all four vectors of electric and magnetic fields E, D, B and H have the same dimensions, in accordance with their physical meaning , therefore, GHS is considered more convenient for theoretical research.

In scientific works, as a rule, the choice of one system or another is determined by continuity of notation and transparency physical meaning than the convenience of measurements.

Story

A system of measures based on the centimeter, gram and second was proposed by the German scientist Gauss in 1832. In 1874, Maxwell and Thomson improved the system by adding electromagnetic units of measurement.

The quantities of many units of the GHS system were found to be inconvenient for practical use, and it was soon replaced by a system based on the meter, kilogram and second (MKS). The GHS continued to be used in parallel with the ISS, mainly in scientific research.

After the adoption of the SI system in 1960, the GHS almost fell out of use in engineering applications, but continues to be widely used, for example, in theoretical physics and astrophysics due to more simple type laws of electromagnetism.

Of the three additional systems, the most widely used is the SGS symmetrical system.

Some units of measurement

- cm/s;
- cm/s²;
- , g cm/s²;
energy - erg, g cm² / s²;
- erg/s, g cm² / s²;
- dyne/cm², g/(cm·s²);
- , g/(cm s);
- , cm²/s;
- (SGSM, Gaussian system);

Systems of units SI and CGS. Some units of measurement

GHS extensions

SGSM

SSSE

SGS symmetrical, or Gaussian system of units

Story

Some units of measurement

see also

See what "SGSE" is in other dictionaries:

More about electric charge

General information

Examples of static electricity

Static electricity and weather

Static electricity in medicine

Other examples

Study of static electricity

Electricity measurement

Gauss system.

GHS system

ISS system.

MTS system.

MKGSS system.

SGSE system

SGSM system

GHS system

Story

Some units of measurement