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Physical quantities. Physical quantities and units of their measurement Physical quantity and unit of quantity

Physical quantities. Physical quantities and units of their measurement Physical quantity and unit of quantity

Physical size called physical property material object, process, physical phenomenon, characterized quantitatively.

Physical quantity value expressed by one or more numbers characterizing this physical quantity, indicating the unit of measurement.

The size of a physical quantity are the values of numbers appearing in the value of a physical quantity.

Units of measurement of physical quantities.

Unit of measurement of physical quantity is a quantity of fixed size that is assigned a numerical value equal to one. It is used for the quantitative expression of physical quantities homogeneous with it. A system of units of physical quantities is a set of basic and derived units based on a certain system of quantities.

Only a few systems of units have become widespread. In most cases, many countries use the metric system.

Basic units.

Measure a physical quantity - means to compare it with another similar physical quantity taken as a unit.

The length of an object is compared with a unit of length, the mass of a body with a unit of weight, etc. But if one researcher measures the length in fathoms and another in feet, it will be difficult for them to compare the two values. Therefore, all physical quantities throughout the world are usually measured in the same units. In 1963, the International System of Units SI (System international - SI) was adopted.

For each physical quantity in the system of units there must be a corresponding unit of measurement. Standard units is its physical implementation.

The length standard is meter- the distance between two strokes applied on a specially shaped rod made of an alloy of platinum and iridium.

Standard time serves as the duration of any regularly repeating process, for which the movement of the Earth around the Sun is chosen: the Earth makes one revolution per year. But the unit of time is taken not to be a year, but give me a sec.

For a unit speed take the speed of such a uniform rectilinear movement, in which the body moves 1 m in 1 s.

A separate unit of measurement is used for area, volume, length, etc. Each unit is determined when choosing a particular standard. But the system of units is much more convenient if only a few units are selected as the main ones, and the rest are determined through the main ones. For example, if the unit of length is a meter, then the unit of area will be a square meter, volume will be a cubic meter, speed will be a meter per second, etc.

Basic units The physical quantities in the International System of Units (SI) are: meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), candela (cd) and mole (mol).

Basic SI units
Magnitude	Unit	Designation
Magnitude	Name	Russian	international



Force electric current
Thermodynamic temperature
The power of light
Quantity of substance

There are also derived SI units that have their own names:

Derived SI units with their own names
	Unit		Derived unit expression
Magnitude	Name	Designation	Through other SI units	Through SI major and supplementary units


Pressure				m -1 ChkgChs -2
Energy, work, amount of heat				m 2 ChkgChs -2
Power, energy flow				m 2 ChkgChs -3
Amount of electricity, electric charge
Electrical voltage, electrical potential				m 2 ChkgChs -3 ChA -1
Electrical capacity				m -2 Chkg -1 Ch 4 Ch 2
Electrical resistance				m 2 ChkgChs -3 ChA -2
Electrical conductivity				m -2 Chkg -1 Ch 3 Ch 2
Flow magnetic induction				m 2 ChkgChs -2 ChA -1
Magnetic induction				kgHs -2 HA -1
Inductance				m 2 ChkgChs -2 ChA -2
Light flow
Illumination				m 2 ChkdChsr
Radioactive source activity	becquerel
Absorbed radiation dose

ANDmeasurements. To obtain an accurate, objective and easily reproducible description of a physical quantity, measurements are used. Without measurements, a physical quantity cannot be characterized quantitatively. Definitions such as “low” or “high” pressure, “low” or “high” temperature reflect only subjective opinions and do not contain comparisons with reference values. When measuring a physical quantity, a certain numerical value is assigned to it.

Measurements are carried out using measuring instruments. There are quite a large number of measuring instruments and devices, from the simplest to the most complex. For example, length is measured with a ruler or tape measure, temperature with a thermometer, width with calipers.

Measuring instruments are classified: by the method of presenting information (displaying or recording), by the method of measurement (direct action and comparison), by the form of presentation of readings (analog and digital), etc.

The following parameters are typical for measuring instruments:

Measuring range- the range of values of the measured quantity for which the device is designed during its normal operation (with a given measurement accuracy).

Sensitivity threshold- the minimum (threshold) value of the measured value, distinguished by the device.

Sensitivity- connects the value of the measured parameter and the corresponding change in the instrument readings.

Accuracy- the ability of the device to indicate the true value of the measured indicator.

Stability- the ability of the device to maintain a given measurement accuracy for a certain time after calibration.

STATE SECURITY SYSTEM
UNITS OF MEASUREMENT

UNITS OF PHYSICAL QUANTITIES

GOST 8.417-81

(ST SEV 1052-78)

USSR STATE COMMITTEE ON STANDARDS

Moscow

DEVELOPED USSR State Committee for Standards PERFORMERSYu.V. Tarbeev,Dr.Tech. sciences; K.P. Shirokov,Dr.Tech. sciences; P.N. Selivanov, Ph.D. tech. sciences; ON THE. EryukhinaINTRODUCED USSR State Committee for Standards Member of Gosstandart OK. IsaevAPPROVED AND PUT INTO EFFECT Resolution State Committee USSR according to standards of March 19, 1981 No. 1449

STATE STANDARD OF THE USSR UNION

State system for ensuring the uniformity of measurements

UNITSPHYSICALSIZE

State system for ensuring the uniformity of measurements.

Units of physical quantities

GOST

8.417-81

(ST SEV 1052-78)

By Decree of the USSR State Committee on Standards dated March 19, 1981 No. 1449, the introduction date was established

from 01/01/1982

This standard establishes units of physical quantities (hereinafter referred to as units) used in the USSR, their names, designations and rules for the use of these units. The standard does not apply to units used in scientific research and when publishing their results, if they do not consider and use the results of measurements of specific physical quantities, as well as units of quantities assessed on conventional scales*. * Conventional scales mean, for example, the Rockwell and Vickers hardness scales and the photosensitivity of photographic materials. The standard complies with ST SEV 1052-78 in terms of general provisions, units of the International System, units not included in SI, rules for the formation of decimal multiples and submultiples, as well as their names and designations, rules for writing unit designations, rules for the formation of coherent derived SI units (see reference Appendix 4).

1. GENERAL PROVISIONS

1.1. The units of the International System of Units*, as well as decimal multiples and submultiples of them, are subject to mandatory use (see Section 2 of this standard). * International System of Units (international abbreviated name - SI, in Russian transcription - SI), adopted in 1960 by the XI General Conference on Weights and Measures (GCPM) and refined at subsequent CGPM. 1.2. It is allowed to use, along with the units according to clause 1.1, units that are not included in the SI, in accordance with clauses. 3.1 and 3.2, their combinations with SI units, as well as some decimal multiples and submultiples of the above units that are widely used in practice. 1.3. It is temporarily allowed to use, along with the units under clause 1.1, units that are not included in SI, in accordance with clause 3.3, as well as some multiples and submultiples of them that have become widespread in practice, combinations of these units with SI units, decimal multiples and submultiples of them them and with units according to clause 3.1. 1.4. In newly developed or revised documentation, as well as publications, the values of quantities must be expressed in SI units, decimal multiples and fractions of them and (or) in units allowed for use in accordance with clause 1.2. It is also allowed in the specified documentation to use units according to clause 3.3, the withdrawal period of which will be established in accordance with international agreements. 1.5. The newly approved normative and technical documentation for measuring instruments must provide for their calibration in SI units, decimal multiples and fractions of them, or in units allowed for use in accordance with clause 1.2. 1.6. Newly developed regulatory and technical documentation on verification methods and means must provide for verification of measuring instruments calibrated in newly introduced units. 1.7. SI units established by this standard and units allowed for use in paragraphs. 3.1 and 3.2 shall apply in educational processes all educational institutions, in textbooks and textbooks. 1.8. Revision of regulatory, technical, design, technological and other technical documentation in which units not provided for by this standard are used, as well as bringing into compliance with paragraphs. 1.1 and 1.2 of this standard for measuring instruments, graduated in units subject to withdrawal, are carried out in accordance with clause 3.4 of this standard. 1.9. In contractual-legal relations for cooperation with foreign countries, with participation in the activities of international organizations, as well as in technical and other documentation supplied abroad along with export products (including transport and consumer packaging), international designations of units are used. In documentation for export products, if this documentation is not sent abroad, it is allowed to use Russian unit designations. (New edition, Amendment No. 1). 1.10. In regulatory and technical design, technological and other technical documentation for various types of products and products used only in the USSR, Russian unit designations are preferably used. At the same time, regardless of what unit designations are used in the documentation for measuring instruments, when indicating units of physical quantities on plates, scales and shields of these measuring instruments, international unit designations are used. (New edition, Amendment No. 2). 1.11. In printed publications it is allowed to use either international or Russian designations of units. The simultaneous use of both types of symbols in the same publication is not allowed, with the exception of publications on units of physical quantities.

2. UNITS OF THE INTERNATIONAL SYSTEM

2.1. The main SI units are given in table. 1.

Table 1

Magnitude
Name	Dimension	Name	Designation	Definition
Name	Dimension	Name	international	Definition
Length				A meter is the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 S [XVII CGPM (1983), Resolution 1].
Weight		kilogram		The kilogram is a unit of mass, equal to mass international prototype of the kilogram [I CGPM (1889) and III CGPM (1901)]
Time				A second is a time equal to 9192631770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom [XIII CGPM (1967), Resolution 1]
Electric current strength				Ampere is force equal to strength unchanging current, which, when passing through two parallel straight conductors of infinite length and negligibly small circular cross-sectional area, located in a vacuum at a distance of 1 m from each other, would cause on each section of a conductor 1 m long an interaction force equal to 2 × 10 -7 N [CIPM (1946), Resolution 2, approved by the IX CGPM (1948)]
Thermodynamic temperature				Kelvin is a unit of thermodynamic temperature equal to 1/273.16 of the thermodynamic temperature of the triple point of water [XIII CGPM (1967), Resolution 4]
Quantity of substance				A mole is the amount of substance in a system containing the same number of structural elements as there are atoms in carbon-12 weighing 0.012 kg.
When using a mole, the structural elements must be specified and may be atoms, molecules, ions, electrons and other particles or specified groups of particles [XIV CGPM (1971), Resolution 3]				The power of light
Candela is the intensity equal to the luminous intensity in a given direction of a source emitting monochromatic radiation with a frequency of 540 × 10 12 Hz, the energetic luminous intensity of which in that direction is 1/683 W/sr [XVI CGPM (1979), Resolution 3] Notes: 1. In addition to the Kelvin temperature (symbol T ) it is also possible to use Celsius temperature (designation t ) it is also possible to use Celsius temperature (designation = ), defined by the expression - Notes: 1. In addition to the Kelvin temperature (symbol T Notes: 1. In addition to the Kelvin temperature (symbol 0 , where Notes: 1. In addition to the Kelvin temperature (symbol 0 = 273.15 K, by definition. Kelvin temperature is expressed in Kelvin, Celsius temperature - in degrees Celsius (international and Russian designation °C). The size of a degree Celsius is equal to a kelvin. ) it is also possible to use Celsius temperature (designation 2. Kelvin temperature interval or difference is expressed in kelvins. The Celsius temperature interval or difference can be expressed in both kelvins and degrees Celsius.

3. The designation of International Practical Temperature in the 1968 International Practical Temperature Scale, if it is necessary to distinguish it from thermodynamic temperature, is formed by adding the index “68” to the designation of thermodynamic temperature (for example, 68 or

68).

4. The uniformity of light measurements is ensured in accordance with GOST 8.023-83.
	Name	Designation	Definition
	Name	international	Definition
(Changed edition, Amendment No. 2, 3).			2.2. Additional SI units are given in table. 2.
table 2	Name of quantity		Flat angle A radian is the angle between two radii of a circle, the length of the arc between which is equal to the radius square with side equal to the radius of the sphere

(Changed edition, Amendment No. 3). 2.3. Derived SI units should be formed from basic and additional SI units according to the rules for the formation of coherent derived units (see mandatory Appendix 1). Derived SI units that have special names can also be used to form other derived SI units. Derived units with special names and examples of other derived units are given in Table. 3 - 5. Note. Electrical and magnetic SI units should be formed in accordance with the rationalized form of the electrical equations.

magnetic field

Table 3

Magnitude
Name	Dimension	Name	Designation
Name	Dimension	Name	international
Examples of derived SI units, the names of which are formed from the names of basic and additional units		Square
square meter		Volume, capacity
cubic meter		Speed
meter per second		Angular velocity
radians per second		Acceleration
meters per second squared		Angular acceleration
radian per second squared		Wave number
meter to the minus first power		Density
kilogram per cubic meter		Specific volume
		cubic meter per kilogram
		ampere per square meter
ampere per meter		Molar concentration
mole per cubic meter		Flow of ionizing particles
second to the minus first power		Particle flux density
second to the minus first power - meter to the minus second power		Brightness

candela per square meter

Table 4

Magnitude
Name	Dimension	Name	Designation	Derived SI units with special names
Name	Dimension	Name	international	Derived SI units with special names
Expression in terms of major and minor, SI units
Frequency
Strength, weight
Pressure, mechanical stress, elastic modulus				Energy, work, amount of heat
m 2 × kg × s -2				Power, energy flow
m 2 × kg × s -3
Electric charge (amount of electricity)				Electrical voltage, electrical potential, electrical potential difference, electromotive force
m 2 × kg × s -3 × A -1	Electrical capacity			L -2 M -1 T 4 I 2
				m -2 × kg -1 × s 4 × A 2
m 2 × kg × s -3 × A -2	Electrical conductivity			L -2 M -1 T 3 I 2
m -2 × kg -1 × s 3 × A 2				Magnetic induction flux, magnetic flux
m 2 × kg × s -2 × A -1				Magnetic flux density, magnetic induction
kg × s -2 × A -1				Inductance, mutual inductance
m 2 × kg × s -2 × A -2
Light flow				Illumination
m -2 × cd × sr		becquerel
Activity of a nuclide in a radioactive source (radionuclide activity) Absorbed radiation dose, kerma, absorbed dose indicator (absorbed dose)
ionizing radiation

(Changed edition, Amendment No. 3).

Equivalent radiation dose

Examples of derived SI units, the names of which are formed using the special names given in table. 4

Magnitude
Name	Dimension	Name	Designation		Expression in terms of SI major and supplementary units
Name	Dimension	Name	international		Expression in terms of SI major and supplementary units
Moment of power		newton meter			Energy, work, amount of heat
Surface tension		Newton per meter
Dynamic viscosity		pascal second			m -1 × kg × s -1
		pendant per cubic meter
Electrical bias		pendant per square meter
		volt per meter			m × kg × s -3 × A -1
Absolute dielectric constant	L -3 M -1 × T 4 I 2	farad per meter			m -3 × kg -1 × s 4 × A 2
Absolute magnetic permeability		henry per meter			m × kg × s -2 × A -2
Specific energy		joule per kilogram
Heat capacity of the system, entropy of the system		joule per kelvin			m 2 × kg × s -2 × K -1
Specific heat capacity, specific entropy		joule per kilogram kelvin		J/(kg × K)	m 2 × s -2 × K -1
Surface density energy flow		watt per square meter
Thermal conductivity		watt per meter kelvin			m × kg × s -3 × K -1
		joule per mole			m 2 × kg × s -2 × mol -1
Molar entropy, molar heat capacity	L 2 MT -2 q -1 N -1	joule per mole kelvin		J/(mol × K)	m 2 × kg × s -2 × K -1 × mol -1
		watt per steradian			m 2 × kg × s -3 × sr -1
Exposure dose (X-ray and gamma radiation)		pendant per kilogram
Absorbed dose rate		gray per second

3. UNITS NOT INCLUDED IN SI

3.1. The units listed in table. 6 are allowed for use without a time limit, along with SI units. 3.2. Without a time limit, it is allowed to use relative and logarithmic units with the exception of the neper unit (see clause 3.3). 3.3. The units given in table. 7 may be temporarily applied until relevant international decisions are taken on them. 3.4. Units, the relationships of which with SI units are given in Reference Appendix 2, are withdrawn from circulation within the time limits provided for by the programs of measures for the transition to SI units, developed in accordance with RD 50-160-79. 3.5. In justified cases in industries National economy It is allowed to use units not provided for by this standard by introducing them into industry standards in agreement with Gosstandart.

Table 6

Non-systemic units allowed for use along with SI units

4. The uniformity of light measurements is ensured in accordance with GOST 8.023-83.				Note
	Name	Designation	Relation to SI unit
	Name	international	Relation to SI unit
Weight
Weight	atomic mass unit		1.66057 × 10 -27 × kg (approx.)
Time 1

			86400 s
(Changed edition, Amendment No. 2, 3).			(p /180) rad = 1.745329… × 10 -2 × rad
			(p /10800) rad = 2.908882… × 10 -4 rad
			(p /648000) rad = 4.848137…10 -6 rad

square meter
Length	astronomical unit		1.49598 × 10 11 m (approx.)
	light year		9.4605 × 10 15 m (approx.)
			3.0857 × 10 16 m (approx.)
Optical power	diopter
Examples of derived SI units, the names of which are formed from the names of basic and additional units
Energy	electron-volt		1.60219 × 10 -19 J (approx.)
Full power	volt-ampere
Reactive power
Mechanical stress	newton per square millimeter
1 It is also possible to use other units that are widely used, for example, week, month, year, century, millennium, etc.

(Changed edition, Amendment No. 3).

2 It is allowed to use the name “gon” 3 It is not recommended to use for precise measurements. If it is possible to shift the designation l with the number 1, the designation L is allowed.

Note. Units of time (minute, hour, day), plane angle (degree, minute, second), astronomical unit, light year, diopter and atomic mass unit are not allowed to be used with prefixes

4. The uniformity of light measurements is ensured in accordance with GOST 8.023-83.				Note
	Name	Designation	Relation to SI unit
	Name	international	Relation to SI unit
Length	Table 7		Units temporarily approved for use	nautical mile
radians per second				1852 m (exactly)
Weight			In maritime navigation	In gravimetry
2 × 10 -4 kg (exactly)			For precious stones and pearls	Linear density
cubic meter				nautical mile
10 -6 kg/m (exactly)	In the textile industry
10 -6 kg/m (exactly)	Rotation frequency		revolutions per second
revolutions per minute
1/60 s -1 = 0.016(6) s -1 Pressure				Natural logarithm

(Changed edition, Amendment No. 3).

dimensionless ratio of a physical quantity to a physical quantity of the same name, taken as the original

1 Np = 0.8686…V = = 8.686… dB

4. RULES FOR THE FORMATION OF DECIMAL MULTIPLES AND MULTIPLE UNITS, AS WELL AS THEIR NAMES AND DESIGNATIONS

4.1. Decimal multiples and submultiples, as well as their names and designations, should be formed using the factors and prefixes given in Table. 8.

Table 8	Factors and prefixes for the formation of decimal multiples and submultiples and their names	Factor	Table 8	Factors and prefixes for the formation of decimal multiples and submultiples and their names	Factor
Table 8		international	Table 8		international

4.2. Attaching two or more prefixes in a row to the name of a unit is not allowed. For example, instead of the name of the unit micromicrofarad, you should write picofarad. Notes: 1 Due to the fact that the name of the basic unit - kilogram - contains the prefix “kilo”, to form multiple and sub-multiple units of mass, the sub-multiple unit of gram (0.001 kg, kg) is used, and the prefixes must be attached to the word “gram”, for example, milligram (mg, mg) instead of microkilogram (m kg, μkg). 2. The submultiple unit of mass - “gram” can be used without attaching a prefix. 4.3. The prefix or its designation should be written together with the name of the unit to which it is attached, or, accordingly, with its designation. 4.4. If a unit is formed as a product or relation of units, the prefix should be attached to the name of the first unit included in the product or relation. It is allowed to use a prefix in the second factor of the product or in the denominator only in justified cases, when such units are widespread and the transition to units formed in accordance with the first part of the paragraph is associated with great difficulties, for example: ton-kilometer (t × km; t × km), watt per square centimeter (W / cm 2; W/cm 2), volt per centimeter (V / cm; V/cm), ampere per square millimeter (A / mm 2; A/mm 2). 4.5. The names of multiples and submultiples of a unit raised to a power should be formed by attaching a prefix to the name of the original unit, for example, to form the names of a multiple or submultiple unit of a unit of area - square meter , representing the second power of the unit of length - the meter, the prefix should be attached to the name of this last unit: square kilometer

, square centimeter, etc. 4.6. Designations of multiples and submultiples of a unit raised to a power should be formed by adding the appropriate exponent to the designation of a multiple or submultiple of that unit, the exponent meaning the exponentiation of a multiple or submultiple unit (together with the prefix). Examples: 1. 5 km 2 = 5(10 3 m) 2 = 5 × 10 6 m 2. 2. 250 cm 3 /s = 250(10 -2 m) 3 /(1 s) = 250 × 10 -6 m 3 /s. 3. 0.002 cm -1 = 0.002(10 -2 m) -1 = 0.002 × 100 m -1 = 0.2 m -1. 4.7. Recommendations for choosing decimal multiples and submultiples are given in Reference Appendix 3.

5.1. To write the values of quantities, units should be designated with letters or special signs (...°,... ¢,... ¢ ¢), and two types of letter designations are established: international (using letters of the Latin or Greek alphabet) and Russian (using letters of the Russian alphabet) . The unit designations established by the standard are given in table. 1 - 7. International and Russian designations for relative and logarithmic units are as follows: percent (%), ppm (o/oo), ppm (pp m, ppm), bel (V, B), decibel (dB, dB), octave (- , oct), decade (-, dec), background (phon, background). 5.2. Letter designations of units must be printed in roman font. In unit designations, a dot is not used as an abbreviation sign. 5.3. Unit designations should be used after numerical values of quantities and placed on the line with them (without moving to the next line). Between the last digit of the number and the designation of the unit, a space should be left equal to the minimum distance between words, which is determined for each type and size of font according to GOST 2.304-81. (Changed edition, Amendment No. 3). Exceptions are designations in the form of a sign raised above the line (clause 5.1), before which a space is not left. 5.4. In the presence of decimal

in the numerical value of a quantity, the unit symbol should be placed after all digits.	5.5. When indicating the values of quantities with maximum deviations, you should enclose the numerical values with maximum deviations in brackets and place unit designations after the brackets or put unit designations after the numerical value of the quantity and after its maximum deviation.	5.6. It is allowed to use unit designations in column headings and in row names (sidebars) of tables. Examples:

Nominal flow. m3/h
Upper limit of readings, m 3
Dividing value of the rightmost roller, m 3, no more
100, 160, 250, 400, 600 and 1000
2500, 4000, 6000 and 10000
Traction power, kW
Overall dimensions, mm:
length
width

height Track, mm, as multiplication signs*. * In typewritten texts, it is allowed not to raise the period. It is allowed to separate the letter designations of units included in the work with spaces, if this does not lead to misunderstanding. 5.9. In letter designations of unit ratios, only one line should be used as a division sign: oblique or horizontal. It is allowed to use unit designations in the form of a product of unit designations raised to powers (positive and negative)**.** If for one of the units included in the relation, the designation is set in the form

negative degree 1

(for example s -1, m -1, K -1; c -1, m -1, K -1), using an oblique or horizontal line is not allowed. 5.10. When using a slash, the unit symbols in the numerator and denominator should be placed on a line, and the product of the unit symbols in the denominator should be enclosed in parentheses.

5.11. When indicating a derived unit consisting of two or more units, it is not allowed to combine letter designations and names of units, i.e. For some units, give designations, and for others, names.

Note. It is allowed to use combinations of special characters...°,... ¢,... ¢ ¢, % and o / oo with letter designations of units, for example...°/ s, etc.

APPLICATION = Mandatory,

RULES FOR FORMATION OF COHERENT DERIVATIVE SI UNITS APPLICATION Coherent derived units (hereinafter referred to as derived units) of the International System, as a rule, are formed using the simplest equations of connections between quantities (defining equations), in which the numerical coefficients are equal to 1. To form derived units, quantities in the connection equations are taken equal to SI units. Example. The unit of speed is formed using an equation that determines the speed of a rectilinearly and uniformly moving point s v ) it is also possible to use Celsius temperature (designation s/t s Where ) it is also possible to use Celsius temperature (designation- speed;

[- length of the traveled path;] = [- time of movement of the point. Substitution instead]/[And their SI units gives

v s t ] = 1 m/s. Therefore, the SI unit of speed is meter per second. He

RULES FOR FORMATION OF COHERENT DERIVATIVE SI UNITS equal to speed a rectilinearly and uniformly moving point, at which this point moves a distance of 1 m in a time of 1 s. If the coupling equation contains a numerical coefficient different from 1, then to form a coherent derivative of an SI unit, values with values in SI units are substituted into the right side, giving, after multiplication by the coefficient, the total numerical value, equal to the number;APPLICATION is the speed of motion of a point, then the coherent SI unit of energy is formed, for example, as follows:

Therefore, the SI unit of energy is the joule (equal to the newton meter). In the examples given, it is equal to the kinetic energy of a body weighing 2 kg moving at a speed of 1 m / s, or a body weighing 1 kg moving at a speed

negative degree 2

Information

Correlation of some non-systemic units with SI units

Name of quantity					Note
	Name	Designation		Relation to SI unit
	Name	international		Relation to SI unit
Length	angstrom
Length	x-unit			1.00206 × 10 -13 m (approx.)
Examples of derived SI units, the names of which are formed from the names of basic and additional units
Weight
table 2	square degree			3.0462... × 10 -4 sr
Frequency
	kilogram-force			9.80665 N (exact)
	kilopond
	gram-force			9.83665 × 10 -3 N (exact)

	ton-force			9806.65 N (exactly)
revolutions per minute	kilogram-force per square centimeter			98066.5 Ra (exactly)
	kilopond per square centimeter
	millimeter of water column		mm water Art.	9.80665 Ra (exactly)
	millimeter of mercury		mmHg Art.

Tension (mechanical)	kilogram-force per square millimeter			9.80665 × 10 6 Ra (exact)
Tension (mechanical)	kilopond per square millimeter			9.80665 × 10 6 Ra (exact)
Work, energy
Power	Horsepower
Dynamic viscosity
Kinematic viscosity
	ohm-square millimeter per meter		Ohm × mm 2 /m
Magnetic flux	Maxwell
Magnetic induction
	gplbert			(10/4 p) A = 0.795775…A
Magnetic field strength				(10 3 / p) A/ m = 79.5775…A/ m
Amount of heat, thermodynamic potential (internal energy, enthalpy, isochoric-isothermal potential), heat of phase transformation, heat chemical reaction	calorie (int.)			4.1858 J (exactly)
	thermochemical calorie			4.1840 J (approx.)
	calorie 15 degrees			4.1855 J (approx.)
Absorbed radiation dose
Equivalent dose of radiation, equivalent dose indicator
Exposure dose of photon radiation (exposure dose of gamma and x-ray radiation)				2.58 × 10 -4 C/kg (exact)
Activity of a nuclide in a radioactive source				3,700 × 10 10 Bq (exact)
Length
Angle of rotation				2 p rad = 6.28… rad
Magnetomotive force, magnetic potential difference	ampereturn
second to the minus first power - meter to the minus second power
Examples of derived SI units, the names of which are formed from the names of basic and additional units

Amended edition, Rev. No. 3.

negative degree 3

Information

1. The choice of a decimal multiple or fractional unit of an SI unit is dictated primarily by the convenience of its use. From the variety of multiple and submultiple units that can be formed using prefixes, a unit is selected that leads to numerical values of the quantity acceptable in practice. In principle, multiples and submultiples are chosen so that the numerical values of the quantity are in the range from 0.1 to 1000. 1.1. In some cases, it is appropriate to use the same multiple or submultiple unit even if the numerical values fall outside the range of 0.1 to 1000, for example, in tables of numerical values for the same quantity or when comparing these values in the same text. 1.2. In some areas the same multiple or submultiple unit is always used. For example, in drawings used in mechanical engineering, linear dimensions are always expressed in millimeters. 2. In table. 1 of this appendix shows the recommended multiples and submultiples of SI units for use. Presented in table. 1 multiples and submultiples of SI units for a given physical quantity should not be considered exhaustive, since they may not cover the ranges of physical quantities in developing and emerging fields of science and technology. However, the recommended multiples and submultiples of SI units contribute to the uniformity of presentation of the values of physical quantities related to various fields of technology. The same table also contains multiples and submultiples of units that are widely used in practice and are used along with SI units. 3. For quantities not covered in table. 1, you should use multiple and submultiple units selected in accordance with paragraph 1 of this appendix. 4. To reduce the likelihood of errors in calculations, it is recommended to substitute decimal multiples and submultiples only in the final result, and during the calculation process, express all quantities in SI units, replacing prefixes with powers of 10. 5. In Table. 2 of this appendix shows the popular units of some logarithmic quantities.

Table 1

4. The uniformity of light measurements is ensured in accordance with GOST 8.023-83.	Designations
	SI units		units not included in SI	multiples and submultiples of non-SI units
Part I. Space and time
(Changed edition, Amendment No. 2, 3).	rad ; rad (radian)	m rad ; mkrad	... ° (degree)... (minute)..." (second)
table 2	sr ; cp (steradian)
Length	m; m (meter)		… ° (degree) … ¢ (minute) … ² (second)
Examples of derived SI units, the names of which are formed from the names of basic and additional units
square meter			l(L); l (liter)
Time	s ; s (second)		d ; day (day) min; min (minute)
cubic meter
radians per second	m/s2; m/s 2
Part II. Periodic and related phenomena
	Hz; Hz (hertz)
10 -6 kg/m (exactly)			min -1 ; min -1
Part III. Mechanics
Weight	kg ; kg (kilogram)		t ; t (ton)
2 × 10 -4 kg (exactly)	kg/m; kg/m	mg/m; mg/m or g/km; g/km
meter to the minus first power	kg/m3; kg/m 3	Mg/m3; Mg/m 3 kg/dm 3; kg/dm 3 g/cm3; g/cm 3	t/m3; t/m 3 or kg/l; kg/l	g/ml; g/ml
Quantity of movement	kg×m/s; kg × m/s
Momentum	kg × m 2 / s; kg × m 2 /s
Moment of inertia (dynamic moment of inertia)	kg × m 2, kg × m 2
Frequency	N; N (newton)
Moment of power	N×m; N×m	MN × m; MN × m kN × m; kN × m mN × m; mN × m m N × m ; µN × m
revolutions per minute	Ra; Pa (pascal)	m Ra; µPa
Voltage
Dynamic viscosity	Ra × s; Pa × s	mPa × s; mPa × s
Kinematic viscosity	m2/s; m 2 /s	mm2/s; mm 2 /s
Surface tension		mN/m; mN/m
Energy, work	J ; J (joule)		(electron-volt)	GeV ; GeV MeV ; MeV keV ; keV
Power	W ; W (watt)
Part IV. Heat
Temperature	TO; K (kelvin)
Temperature coefficient
Heat, amount of heat
Heat flow
Thermal conductivity
Heat transfer coefficient	W/(m 2 × K)
Heat capacity		kJ/K; kJ/K
Specific heat	J/(kg × K)	kJ /(kg × K); kJ/(kg × K)
Entropy		kJ/K; kJ/K
Specific entropy	J/(kg × K)	kJ/(kg × K); kJ/(kg × K)
Specific heat	J/kg; J/kg	MJ/kg; MJ/kg kJ / kg ; kJ/kg
Specific heat of phase transformation	J/kg; J/kg	MJ/kg; MJ/kg kJ/kg; kJ/kg
Part V. Electricity and magnetism
Electric current (electric current strength)	A; A (amps)
Electric charge (amount of electricity)	WITH; Cl (pendant)
Spatial density of electric charge	C/ m 3; C/m 3	C/mm 3; C/mm 3 MS/ m 3 ; MC/m 3 S/s m 3 ; C/cm 3 kC/m3; kC/m 3 m C/ m 3; mC/m 3 m C/ m 3; µC/m 3
Surface electric charge density	S/ m 2, C/m 2	MS/ m 2 ; MC/m 2 С/ mm 2; C/mm 2 S/s m 2 ; C/cm 2 kC/m2; kC/m 2 m C/ m 2; mC/m 2 m C/ m 2; µC/m 2
Electric field strength		MV/m; MV/m kV/m; kV/m V/mm; V/mm V/cm; V/cm mV/m; mV/m mV/m; µV/m
Electrical voltage, electrical potential, electrical potential difference, electromotive force	V, V (volts)
Electrical bias	C/ m 2; C/m 2	S/s m 2 ; C/cm 2 kC/cm2; kC/cm 2 m C/ m 2; mC/m 2 m C/ m 2, µC/m 2
Electrical displacement flux
m 2 × kg × s -3 × A -1	F, Ф (farad)
Absolute dielectric constant, electrical constant		m F / m , µF/m nF/m, nF/m pF / m , pF/m
Polarization	S/ m 2, C/m 2	S/s m 2, C/cm 2 kC/m2; kC/m 2 m C/ m 2, mC/m 2 m C/ m 2; µC/m 2
Electric dipole moment	S × m, Cl × m
Electric current density	A/ m 2, A/m 2	MA/ m 2, MA/m 2 A/mm 2, A/mm 2 A/s m 2, A/cm 2 kA/m2, kA/m2,
Linear electric current density		kA/m; kA/m A/mm; A/mm A/c m ; A/cm
Magnetic field strength		kA/m; kA/m A/mm; A/mm A/cm; A/cm
Magnetomotive force, magnetic potential difference
Magnetic induction, magnetic flux density	T; Tl (tesla)
Magnetic flux	Wb, Wb (weber)
Magnetic vector potential	T × m; T × m	kT×m; kT × m
Inductance, mutual inductance	N; Gn (Henry)
Absolute magnetic permeability, magnetic constant		m N/ m; µH/m nH/m; nH/m
Magnetic moment	A × m 2; A m 2
Magnetization		kA/m; kA/m A/mm; A/mm
Magnetic polarization
Electrical resistance
m 2 × kg × s -3 × A -2	S ; CM (Siemens)
Electrical resistivity	W×m; Ohm × m	GW×m; GΩ × m M W × m; MΩ × m kW×m; kOhm × m W×cm; Ohm × cm mW×m; mOhm × m mW×m; µOhm × m nW×m; nΩ × m
Electrical conductivity		MS/m; MSm/m kS/m; kS/m
Reluctance
Magnetic conductivity
Impedance
Impedance module
Reactance
Active resistance
Admittance
Conductivity module
Reactive conductivity
Conductance
Active power
Reactive power
Full power			V × A, V × A
Part VI. Light and related electromagnetic radiation
Wavelength
radian per second squared
Radiation energy
Radiation flux, radiation power
Energy luminous intensity (radiant intensity)	W/sr; Tue/Wed
Energy brightness (radiance)	W /(sr × m 2); W/(avg × m2)
Energy illumination (irradiance)	W/m2; W/m2
Energetic luminosity (radiance)	W/m2; W/m2
When using a mole, the structural elements must be specified and may be atoms, molecules, ions, electrons and other particles or specified groups of particles [XIV CGPM (1971), Resolution 3]
m 2 × kg × s -2 × A -2	lm ; lm (lumen)
Light energy	lm×s; lm × s		lm × h; lm × h
second to the minus first power - meter to the minus second power	cd/m2; cd/m2
Luminosity	lm/m2; lm/m 2
Light flow	l x; lux (lux)
Light exposure	lx×s; lx × s
Light equivalent of radiation flux	lm/W; lm/W
Part VII. Acoustics
Period
Batch frequency
Wavelength
Sound pressure		m Ra; µPa
Particle oscillation speed		mm/s; mm/s
Volume velocity	m3/s; m 3 /s
Sound speed
Sound energy flow, sound power
Sound intensity	W/m2; W/m2	mW/m2; mW/m2 mW/m2; µW/m 2 pW/m2; pW/m2
Specific acoustic impedance	Pa×s/m; Pa × s/m
Acoustic impedance	Pa×s/m3; Pa × s/m 3
Mechanical resistance	N×s/m; N × s/m
Equivalent absorption area of a surface or object
Reverberation time
Part VIII Physical chemistry and molecular physics
Quantity of substance	mol; mole (mol)	kmol; kmol mmol; mmol m mol; µmol
Molar mass	kg/mol; kg/mol	g/mol; g/mol
Molar volume	m3/moi; m 3 /mol	dm 3/mol; dm 3 /mol cm 3 / mol; cm 3 /mol	l/mol; l/mol
Molar internal energy	J/mol; J/mol	kJ/mol; kJ/mol
Molar enthalpy	J/mol; J/mol	kJ/mol; kJ/mol
Chemical Potential	J/mol; J/mol	kJ/mol; kJ/mol
Chemical affinity	J/mol; J/mol	kJ/mol; kJ/mol
Molar heat capacity	J/(mol × K); J/(mol × K)
Molar entropy	J/(mol × K); J/(mol × K)
ampere per meter	mol/m3; mol/m 3	kmol/m3; kmol/m 3 mol/dm 3; mol/dm 3	mol/1; mol/l
Specific adsorption	mol/kg; mol/kg	mmol/kg; mmol/kg
Thermal diffusivity	M2/s; m 2 /s
Part IX. Ionizing radiation
Absorbed dose of radiation, kerma, absorbed dose indicator (absorbed dose of ionizing radiation)	Gy ; Gr (gray)	m G y; µGy
Activity of a nuclide in a radioactive source (radionuclide activity)	Bq ; Bq (becquerel)

(Changed edition, Amendment No. 3).

68).

Name of logarithmic quantity	Unit designation	Initial value of the quantity
Sound pressure level
Sound power level
Sound intensity level
Power Level Difference
Strengthening, weakening
Attenuation coefficient

negative degree 4

Information

INFORMATION DATA ABOUT COMPLIANCE WITH GOST 8.417-81 ST SEV 1052-78

1. Sections 1 - 3 (clauses 3.1 and 3.2); 4, 5 and the mandatory Appendix 1 to GOST 8.417-81 correspond to sections 1 - 5 and the appendix to ST SEV 1052-78. 2. Reference appendix 3 to GOST 8.417-81 corresponds to the information appendix to ST SEV 1052-78.

Physical quantity - a property of physical objects that is qualitatively common to many objects, but quantitatively individual for each of them. The qualitative side of the concept “physical quantity” determines its type (for example, electrical resistance as general property conductors of electricity), and quantitative - its “size” (the value of the electrical resistance of a particular conductor, for example R = 100 Ohms). The numerical value of the measurement result depends on the choice of unit of physical quantity.

Physical quantities are assigned alphabetic symbols used in physical equations expressing relationships between physical quantities that exist in physical objects.

Size of physical quantity - quantitative determination of a value inherent in a specific object, system, phenomenon or process.

Physical quantity value- assessment of the size of a physical quantity in the form of a certain number of units of measurement accepted for it. Numerical value of a physical quantity- an abstract number expressing the ratio of the value of a physical quantity to the corresponding unit of a given physical quantity (for example, 220 V is the value of the voltage amplitude, and the number 220 itself is a numerical value). It is the term “value” that should be used to express the quantitative side of the property under consideration. It is incorrect to say and write “current value”, “voltage value”, etc., since current and voltage are themselves quantities (the correct use of the terms “current value”, “voltage value”).

With a selected assessment of a physical quantity, it is characterized by true, actual and measured values.

The true value of a physical quantity They call the value of a physical quantity that would ideally reflect the corresponding property of an object in qualitative and quantitative terms. It is impossible to determine it experimentally due to inevitable measurement errors.

This concept is based on two main postulates of metrology:

§ the true value of the quantity being determined exists and is constant;

§ the true value of the measured quantity cannot be found.

In practice, they operate with the concept of a real value, the degree of approximation of which to the true value depends on the accuracy of the measuring instrument and the error of the measurements themselves.

The actual value of a physical quantity they call it a value found experimentally and so close to the true value that for a certain purpose it can be used instead.

Under measured value understand the value of the quantity measured by the indicator device of the measuring instrument.

Unit of physical quantity - a fixed-size value, which is conventionally assigned a standard numerical value equal to one.

Units of physical quantities are divided into basic and derivative and combined into systems of units of physical quantities. The unit of measurement is established for each of the physical quantities, taking into account the fact that many quantities are interconnected by certain dependencies. Therefore, only some of the physical quantities and their units are determined independently of the others. Such quantities are called main. Other physical quantities - derivatives and they are found using physical laws and dependencies through core. A set of basic and derived units of physical quantities, formed in accordance with accepted principles, is called system of units of physical quantities. The unit of a basic physical quantity is basic unit systems.

International system of units (SI system; SI - French. Systeme International) was adopted by the XI General Conference on Weights and Measures in 1960.

The SI system is based on seven basic and two additional physical units. Basic units: meter, kilogram, second, ampere, kelvin, mole and candela (Table 1).

Table 1. International SI units


Name	Dimension	Name	Designation
international
Basic

		kilogram

Electric current strength
Temperature
Quantity of substance
The power of light
Additional
Flat angle
Solid angle		Name of quantity

Meter equal to the distance, traveled by light in a vacuum in 1/299792458 of a second.

Kilogram- a unit of mass defined as the mass of the international prototype kilogram, representing a cylinder made of an alloy of platinum and iridium.

Second is equal to 9192631770 periods of radiation corresponding to the energy transition between two levels of the hyperfine structure of the ground state of the cesium-133 atom.

Ampere- the strength of a constant current, which, passing through two parallel straight conductors of infinite length and negligibly small circular cross-sectional area, located at a distance of 1 m from each other in a vacuum, would cause an interaction force equal to 210 -7 N (newton) on each section of the conductor 1 m long.

Kelvin- a unit of thermodynamic temperature equal to 1/273.16 of the thermodynamic temperature of the triple point of water, i.e., the temperature at which the three phases of water - vapor, liquid and solid - are in dynamic equilibrium.

Mole- the amount of substance containing as many structural elements as are contained in carbon-12 weighing 0.012 kg.

Candela- the intensity of light in a given direction of a source emitting monochromatic radiation with a frequency of 54010 12 Hz (wavelength about 0.555 microns), whose energy radiation intensity in this direction is 1/683 W/sr (sr - steradian).

Additional units SI systems are intended only to form units of angular velocity and angular acceleration. Additional physical quantities of the SI system include plane and solid angles.

Radian (glad) - the angle between two radii of a circle whose arc length is equal to this radius. In practical cases, the following units of measurement of angular quantities are often used:

degree - 1 _ = 2p/360 rad = 1.745310 -2 rad;

minute - 1" = 1 _ /60 = 2.9088 10 -4 rad;

second - 1"= 1"/60= 1 _ /3600 = 4.848110 -6 rad;

radian - 1 rad = 57 _ 17 "45" = 57.2961 _ = (3.4378 10 3)" = (2.062710 5)".

Steradian (Wed) - a solid angle with a vertex at the center of the sphere, cutting out an area on its surface equal to the area of a square with a side equal to the radius of the sphere.

Measure solid angles using plane angles and calculation

Where b- solid angle; ts- a plane angle at the vertex of a cone formed inside a sphere by a given solid angle.

Derived units of the SI system are formed from basic and supplementary units.

In the field of measurements of electrical and magnetic quantities, there is one basic unit - ampere (A). Through the ampere and the unit of power - watt (W), common for electrical, magnetic, mechanical and thermal quantities, all other electrical and magnetic units can be determined. However, today there are no sufficiently accurate means of reproducing watt absolute methods. Therefore, electrical and magnetic units are based on units of current and the ampere-derived unit of capacitance, the farad.

Physical quantities derived from ampere also include:

§ unit of electromotive force (EMF) and electrical voltage - volt (V);

§ unit of frequency - hertz (Hz);

§ unit of electrical resistance - ohm (Ohm);

§ unit of inductance and mutual inductance of two coils - henry (H).

In table 2 and 3 show the derived units most used in telecommunication systems and radio engineering.

Table 2. Derived SI units

Magnitude
Name	Dimension	Name	Designation
international

Energy, work, amount of heat
Strength, weight
Power, energy flow
Amount of electricity
Electrical voltage, electromotive force (EMF), potential
Electrical capacity	Electrical capacity
Electrical resistance
Electrical conductivity	Electrical conductivity
Magnetic induction
Magnetic induction flux
Inductance, mutual inductance

Table 3. SI units used in measurement practice

Magnitude
Name	Dimension	Unit	Designation
international
Electric current density		ampere per square meter
Electric field strength		volt per meter
Absolute dielectric constant	L 3 M -1 T 4 I 2	farad per meter
Electrical resistivity		ohm per meter
Total power of the electrical circuit		volt-ampere
Reactive power of an electrical circuit
Magnetic field strength		ampere per square meter

Abbreviations for units, both international and Russian, named after great scientists, are written in capital letters, for example ampere - A; om - Om; volt - V; farad - F. For comparison: meter - m, second - s, kilogram - kg.

In practice, the use of whole units is not always convenient, since very large or very small values are obtained as a result of measurements. Therefore, the SI system has its decimal multiples and submultiples, which are formed using multipliers. Multiple and submultiple units of quantities are written together with the name of the main or derived unit: kilometer (km), millivolt (mV); megaohm (MΩ).

Multiple unit of physical quantity- a unit greater than an integer number of times the system one, for example kilohertz (10 3 Hz). Submultiple unit of physical quantity- a unit that is an integer times smaller than the system one, for example a microhenry (10 -6 H).

The names of multiple and submultiple units of the SI system contain a number of prefixes corresponding to the factors (Table 4).

Table 4. Factors and prefixes for the formation of decimal multiples and submultiples of SI units

Table 8	Factors and prefixes for the formation of decimal multiples and submultiples and their names	Factor
international

For a quantitative description of various properties of physical objects, physical systems, phenomena or processes, RMG 29-99 (Recommendations for interstate standardization) introduced the concept quantities.

Magnitude- this is a property that can be distinguished from other properties and assessed in one way or another, including quantitatively.

The quantities are divided into perfect And real .

Ideal values mainly relate to the field of mathematics and are a generalization (model) of specific real concepts. They are calculated in one way or another.

Real values are divided into physical and non-physical.

Physical quantity in the general case, it can be defined as a quantity characteristic of certain material objects (processes, phenomena) studied in the natural (physics, chemistry) and technical sciences. Physical quantities include mass, temperature, time, length, voltage, pressure, speed, etc.

TO non-physical These include quantities inherent in social (non-physical) sciences - philosophy, sociology, economics, etc. Non-physical quantities for which a unit of measurement cannot be entered can only be estimated. Examples of non-physical quantities: student assessment on a 5-point scale, the number of employees in an organization, the price of a product, tax rate, etc. The assessment of non-physical quantities is not part of the tasks of theoretical metrology.

Physical quantity– one of the properties of a physical object, common in a qualitative sense for many physical objects, but quantitatively individual for each of them (the qualitative side determines the “kind” of a quantity, for example, electrical resistance as a general property of conductors of electricity, and the quantitative side – its “size” ", for example, the resistance of a particular conductor).

There are physical quantities measurable Where assessed.

Measured physical quantities can be expressed quantitatively in terms of a specific number of established units of measurement.

Estimated physical quantities– quantities for which, for some reason, a unit of measurement cannot be entered, and they can only be estimated.

Assessment– the operation of assigning a certain number of units accepted for it to a given physical quantity, carried out according to established rules. Assessment is carried out using scales.

To express the quantitative content of a property of a particular object, the concept of “size of physical quantity” is used, the assessment of which is established during the measurement process.

Size of physical quantity(size of a quantity) is the quantitative determination of a physical quantity inherent in a specific material object, system, phenomenon or process.

For example, each person has a certain height and weight, as a result of which people can be distinguished by their height or weight, i.e. according to the sizes of the physical quantities that interest us.

Size is an objective quantitative characteristic that does not depend on the choice of units of measurement.

For example, if we write 3.5 kg and 3500 g, then these are two representations of the same size. Each of them is meaning physical quantity (in in this case– masses).

Physical quantity value is an expression of the size of a physical quantity in the form of a certain number of units accepted for it.

Physical quantity value Q obtained as a result of measurement and calculated in accordance with basic measurement equation:

Q = q[Q], (1)

where q is an abstract number called numerical value, and [Q] – unit size measurement of a given physical quantity.

Numerical value of a physical quantity– an abstract number expressing the ratio of the value of a quantity to the corresponding unit of a given physical quantity.

Numeric value The measurement result will depend on the choice of unit of physical quantity. (Example about a boa constrictor from a cartoon).

The numbers 3.5 and 3500 are abstract numbers included in the value of a physical quantity and indicating the numerical values of a physical quantity. In the example given, the mass of the object is given by the numbers - 3.5 and 3500, and the units are kilogram (kg) and gram (g).

Meaning values should not be confused with size. Size of physical quantity of this object exists really and regardless of whether we know it or not, whether we express it in any units or not. The value of a physical quantity appears only after the size of the quantity of a given object is expressed using some unit.

Unit of physical quantity- a physical quantity of a fixed size, which is conditionally assigned a numerical value equal to one. It is used for the quantitative expression of homogeneous physical quantities.

Homogeneous physical quantities are physical quantities that are expressed in the same units and can be compared with each other (for example, the length and diameter of a part).

Physical quantities are combined into system.

System of physical quantities(system of quantities) is a set of physical quantities formed in accordance with accepted principles, when some quantities are taken as independent, and others are determined as functions of these independent quantities.

All quantities included in the system of physical quantities are divided into basic Where derivatives.

Basic physical quantity- a physical quantity included in a system of quantities and conventionally accepted as independent of other quantities of this system.

Derived physical quantity– a physical quantity included in a system of quantities and determined through the basic quantities of this system.

A formalized reflection of the qualitative difference in physical quantities is their dimension.

Dimension of a physical quantity - this is an expression reflecting the relationship of a given quantity with physical quantities accepted in a given system of units as basic ones with a proportionality coefficient equal to one.

The dimension of a physical quantity is indicated by the symbol dim (from the Latin dimension - dimension).

The dimensions of basic physical quantities are indicated by the corresponding capital letters:

length - dim l = L

mass - dim m = M

time - dim t = Notes: 1. In addition to the Kelvin temperature (symbol

electric current strength – dim i= I

thermodynamic temperature – dim Q = Q

amount of substance - dim n = N

luminous intensity – dim j = J

Dimension dim x any derivative of a physical quantity X determined through the equation of connection between quantities. It has the form of a product of basic quantities raised to the appropriate powers:

dim x = L a M b T g I e Q i N v J t ,(2)

where L, M, T, I... - symbols of the main quantities of this system;

a, b, g, e... - indicators of dimension, each of which can be positive or negative, an integer or fractional number, as well as zero.

Dimension indicator - exponent to which the dimension of a basic physical quantity included in the dimension of a derivative physical quantity is raised.

According to the presence of dimension, physical quantities are divided into dimensional Where dimensionless.

Dimensional physical quantity– a physical quantity in the dimension of which at least one of the basic physical quantities is raised to a power not equal to zero.

Dimensionless physical quantity– all dimension indicators are equal to zero. They do not have units of measurement, that is, they are not measured in anything ( For example, friction coefficient).

Measurement scales

Assessment and measurement of physical quantities is carried out using various scales.

Measurement scale is an ordered set of values of a physical quantity that serves as the basis for its measurement.

Let us explain this concept using the example of temperature scales. In the Celsius scale, the melting temperature of ice is taken as the starting point, and the boiling point of water is taken as the main interval (reference point). One hundredth of this interval is the unit of temperature (degree Celsius).

The following main types are distinguished: measurement scales: names, order, differences (intervals), ratios and absolute scales.

Name scales reflect quality properties. The elements of these scales are characterized only by relations of equivalence (equality) and similarity of specific qualitative manifestations of properties.

An example of such scales is the scale for classifying (evaluating) the color of objects by name (red, orange, yellow, green, etc.), based on standardized color atlases, systematized by similarity. Measurements in the color scale are made by comparing, under certain lighting, color samples from the atlas with the color of the object under study and establishing the equality (equivalence) of their colors.

The naming scales do not contain such concepts as “zero”, “unit of measurement”, “dimension”, “more” or “less”. The naming scale can consist of any symbols (number, name, other symbols). The numbers or numbers of such a scale are nothing more than code signs.

The naming scale allows you to make classifications, identify and distinguish objects.

Order scale(rank scale) - arranges objects relative to any of their properties in descending or ascending order.

The resulting ordered series is called ranked. He can give answers to the questions: “What is more or less?”, “What is worse or better?”. The order scale cannot provide more detailed information - how much more or less, how many times better or worse.

An example of an order scale is a group of people built by height, where each subsequent one is lower than all the previous ones; knowledge scoring; athlete's place; wind (Beaufort scale) and earthquake (Richter scale) scales; scales of hardness numbers (Rockwell, Brinell, Vickers scales), etc.

Order scales may or may not have a zero element ( for example, ranked accuracy classes of instruments (0,1 and 2)).

Using order scales, you can measure qualitative indicators that do not have a strict quantitative measure. These scales are especially widely used in humanities: pedagogy, psychology, sociology.

Difference scale(intervals) contains the difference between the values of a physical quantity. For these scales, relations of equivalence, order, and summation of intervals (differences) between quantitative manifestations of properties make sense.

This scale consists of identical intervals, has a conventional (accepted by agreement) unit of measurement and an arbitrarily chosen reference point - zero.

Measurements are based on comparison of identical properties of material objects. For properties for which physical methods are used for quantitative comparison, metrology has established a single generalized concept - a physical quantity. Physical quantity- a property that is qualitatively common to many physical objects, but quantitatively individual for each object, for example, length, mass, electrical conductivity and heat capacity of bodies, gas pressure in a vessel, etc. But smell is not a physical quantity, since it is established using subjective sensations.

A measure for quantitative comparison of identical properties of objects is unit of physical quantity - a physical quantity that, by agreement, is assigned a numerical value equal to 1. Units of physical quantities are assigned a full and abbreviated symbolic designation - dimension.

For example, mass - kilogram (kg), time - second (s), length - meter (m), force - Newton (N). The value of a physical quantity is

assessment of a physical quantity in the form of a certain number of units accepted for it characterizes the quantitative individuality of objects. For example, the diameter of the hole is 0.5 mm, the radius of the globe is 6378 km, the speed of the runner is 8 m/s, the speed of light is 3 10 5 m/s. By measuring is called finding the value of a physical quantity using special technical means . For example, measuring the shaft diameter with a caliper or micrometer, liquid temperature with a thermometer, gas pressure with a pressure gauge or vacuum gauge. Physical quantity value x^, obtained during measurement is determined by the formula x^ = ai, Where A-

numerical value (size) of a physical quantity; and is a unit of physical quantity. Since the values of physical quantities are found experimentally, they contain measurement error. In this regard, a distinction is made between true and actual values of physical quantities. True meaning -

the value of a physical quantity that ideally reflects the corresponding property of an object in qualitative and quantitative terms. It is the limit to which the value of a physical quantity approaches with increasing measurement accuracy. a value of a physical quantity found experimentally that is so close to the true value that it can be used instead for a certain purpose. This value varies depending on the required measurement accuracy. In technical measurements, the value of a physical quantity found with an acceptable error is accepted as the actual value.

Measurement error is the deviation of the measurement result from the true value of the measured value. Absolute error called the measurement error expressed in units of the measured value: Oh = x^- x, Where X- the true value of the measured quantity. Relative error - attitude absolute error measurements to the true value of a physical quantity: 6=Ax/x. The relative error can also be expressed as a percentage.

Since the true value of the measurement remains unknown, in practice only an approximate estimate of the measurement error can be found. In this case, instead of the true value, the actual value of a physical quantity is taken, obtained by measuring the same quantity with a higher accuracy. For example, the error in measuring linear dimensions with a caliper is ±0.1 mm, and with a micrometer - ± 0.004 mm.

The measurement accuracy can be expressed quantitatively as the reciprocal of the relative error modulus. For example, if the measurement error is ±0.01, then the measurement accuracy is 100.