In the International System of Units, what are the basic physical quantities

The International System of Units (SI) is a consistent system of units recommended by the International Conference on Weights and Measures (CGPM). In the International System of Units, units are divided into three categories: basic units, derived units, and auxiliary units.

The 7 strictly defined basic units are: length (meters), mass (kilograms), time (seconds), electric current (amps), thermodynamic temperature (kelvin), amount of matter (moles), and luminous intensity (candela). The basic units are dimensionally independent of each other.

There are many export units, all of which are composed of a combination of basic units. There are currently only two auxiliary units, which are purely geometric units. Of course, auxiliary units can also be reconstituted as export units[1] .

The various physical quantities are interconnected with each other by the equations that describe the laws of nature and their definitions. For convenience, a set of physical quantities that are independent of each other is selected as the basic quantity, and the other quantities are expressed according to the basic quantity and the relevant equations, which are called derived quantities. [1]

In 1948, the 9th International Conference on Weights and Measures (CIPM) instructed the International Commission on Weights and Measures (CIPM) to "study and formulate a set of rules for units of measurement" in an effort to establish a scientific and practical system of units of measurement. In 1954, the 10th International Conference on Weights and Measures decided to adopt the six quantities of length, mass, time, current, thermodynamic temperature and luminous intensity as the basic quantities of the practical unit of measurement. In 1960, the 11th International Conference on Weights and Measures (CIME) decided to name this practical unit of measurement as the International System of Units, with SI as the common abbreviation of the International System of Units. Establish rules for prefixes (called SI prefixes), SI derivation units, and SI auxiliary units, as well as other provisions, to form a set of rules for units of measurement.

In 1971, the 14th International Conference on Weights and Measures decided to add "the quantity of matter" as the seventh basic quantity of the International System of Units on the basis of the previous six quantities, and adopted their corresponding units as the basic units of the International System of Units.

Unit of length: meters (m).

Time unit: seconds (s).

Weight unit: kilogram (kg).

Current unit: ampere (a).

Thermodynamic temperature: on (k).

The unit of quantity of a substance: mole (mol).

Luminous intensity: Candela (CD).

7 Fundamental Physical Quantities:

Mass, in kg

Length, unit: m

Time, unit: s

Current intensity, unit: a (the basic physical quantity of electricity is not the amount of charge, but the amount of electric current) temperature, unit: k

Luminous intensity, unit: cd

The amount of a substance, unit: mol

Length m m

Mass kg kg

Time seconds

Current Ampere [amperere] a

Thermodynamic temperature on [Ervin] k

Luminous intensity: Candela (CD).

The amount of a substance is mol

Length m m

Weight kg kg

Time seconds

Current intensity Amps a

Thermodynamic temperature on [Ervin] k

The amount of a substance is mol

Luminous intensity: Candela (CD).

Length m m

In May, a special committee of French scientists recommended that one 40 millionth of the length of the Earth's meridian passing through Paris be used as the unit of length - the meter.

11th International Conference on Weights and Measures: "The length of the meter is equal to the 1650763 of the wavelength of the radiation in a vacuum of 86 times the wavelength of the transition between the 2p10 and 5d1 energy levels of the Krypton atom in a vacuum".

The 17th International Conference on Weights and Measures, held in Paris in October: "The meter is the length of the journey of light in a vacuum in a time interval of 1 299792458 second".

Mass kg kg

In 1967, the 13th International Conference on Weights and Measures adopted a resolution replacing the astronomical definition of seconds with the following definition: one second is the duration of 9,192,631,770 cycles of transition radiation between two hyperfine energy levels of the ground state of the cesium-133 atom.

International atomic time is an international reference time scale based on the definition of the above seconds, which belongs to the International System of Units (SI).

Current Ampere [amperere] a

The ampere is a constant current, and if kept in a vacuum within two indefinitely long parallel straight wires of negligible circular cross-section, which are 1 metre apart, the force generated between the two wires is equal to 2 10-7 Newtons per metre of length. This definition was approved at the 9th International Conference on Weights and Measures in 1948, and at the 11th International Conference on Weights and Measures in 1960, the ampere was officially adopted as one of the basic units of the International System of Units. Ampere is in honor of the French physicist A

m.Ampere.

Thermodynamic temperature on [Ervin] k

Kelvin English is the abbreviation of kelvin, the international code K, the unit of thermodynamic temperature. Kelvin is one of the 7 basic units in the International System of Units (SI), with absolute zero (0K) as the minimum temperature, the temperature of the triple point of water is specified as , 1k is equal to 1 of the temperature of the triple point of water, and the relationship between the thermodynamic temperature t and the customary Celsius temperature t is t t, because the freezing point temperature of water is approximately equal to , and the unit of thermodynamic temperature (k) is exactly the same as the unit of Celsius temperature ( ). Kell or Chinese was named in honor of the British physicist Lord Kelvin.

Luminous intensity: Candela (CD).

Candela is the luminous intensity of a light source in a given direction, which emits monochromatic radiation with a frequency of 540 1012 Hz and an intensity of 1 683 watts per spherical degree in this direction

The defined 540 1012 Hz radiation wavelength is about 555 nm, which is the most sensitive wavelength to the human eye

The quantity of matter - the physical quantity that indicates the number of particles that make up the substance (the quantity of matter is a proper noun, indivisible and omitted).

Mole – is the unit (mol) of the quantity of a physical quantity substance

According to scientific determinations, the number of c atoms contained in 12 grams of 12C is represented by the symbol NA, which is called the Avogadro constant.

Avogadro's constant (NA) approximation.

Definition: Any substance containing a structural particle (approx.) of the Avogadro constant, the amount of which is 1 mo.

7 Fundamental Physical Quantities:

Mass, in kg

Length, unit: m

Time, unit: s

Current intensity, unit: a (the basic physical quantity of electricity is not the amount of charge, but the amount of electric current) temperature, unit: k

Luminous intensity, unit: cd

The amount of a substance, unit: mol

Units of length: meters; Units of mass: kilograms; Units of time: seconds; Units of current: amps; Units of thermodynamic temperature: Kelvin; The unit of the amount of matter: mole; Unit of luminous intensity: candela.

1.Length: Unit: meters. 1 meter is the travel of light in a vacuum in a time interval of 1 299792458 seconds.

2.Mass: Unit: kilogram (kg): 1 kilogram is the weight of 18 14074481 C-12 atoms.

The duration of the 9192631770 cycle.

4.Current: Unit:

Ampere: In a vacuum, two straight wires of infinite length with a negligible circular cross-section pass through a constant current in a vacuum, and if this constant current is such that the force generated between the two wires is equal to 2 10 N per metre of protective length, then the current intensity of the constant current is 1 A.

5.Thermodynamic temperature: Unit: open (Kelvin): 1 open is 1 of the thermodynamic temperature of the three-phase point of water.

6.The quantity of matter: Unit: Mo (mole): 1 Mo is the amount of matter in a system, and the basic unit contained in the system is equal to the number of atoms in kilograms of carbon-12.

7.Luminous intensity: Unit: kan (candela): 1kan is the luminous intensity of a light source in a given direction, the light source emits monochromatic radiation with a frequency of 540 10 Hz, and the radiation intensity in this direction is 1 683 watts per spherical degree.

Length: The broad base unit is meters.

Mass: The basic unit is the kilogram of liquid sail and hail.

Current: The basic unit is amperes.

The amount of matter: the basic unit mole.

Temperature (Absolute): Kelvin Luminous Intensity: Candela

Untie; a, kg is the base unit, and n is not the base unit so a is wrong b, n is not the base unit, s is the base unit so b is wrong c, m st, j are all derived units, not the base unit so c is wrong d, kg, m are all base units so d is correct so d is selected

m(v l) unit physical quantity name acceleration.

Root number (l g) unit s physical quantity name pendulum period.

The landlord seems to be a really good student, it's good to be able to think of this, but the questions you ask are indeed a little more than junior high school students can understand, you can ask your teachers or related professionals after class for consultation, here, I wish you progress in your studies, every day up. If it still can't solve your problem, you can continue to ask and try your best to help you solve it.

Length (m), mass (kg), time (s), current intensity (a), luminous intensity (cd), temperature ( ) and amount of matter (mol) are all pushed out by these 7 basic units.

The amount of matter is the number of particles contained in 1mol (which can be understood as a unit volume, of course, this volume is very small, so mol is used).

a The quantity, mass, and length of the substance are all basic physical quantities in the International System of Units, so a is correct;

b The unit of quantity of a substance is mol, and the unit of mass of a substance is g, and the two are different physical quantities, so b is wrong;

c The quantity of matter is the basic physical quantity, which is expressed in units, and the unit of the old guess quantity of matter is mol, so c is wrong;

d mole is the unit of the quantity of matter, and the servant form is not the unit of the number of particles, so d is wrong;

So choose A