WHAT ARE THE FUNDAMENTAL QUANTITIES? - SCIENCE - 2025

The fundamental quantities by definition are physical quantities that are so called because they can not be defined in terms of others; that is to say, they are independent and from them other so many magnitudes of different kinds are obtained or derived.

Length, for example, is a fundamental quantity; while the surface is not, as it is defined in terms of length. Similarly, the length quantity cannot be defined in terms of the surface quantity.

Time is one of the most relevant fundamental quantities in science. Source: Pixabay.

A physical quantity is understood to be a property of a material or system that can be measured or quantified. It can also be defined as the combination of magnitude and a unit. Mass, a physical quantity, is expressed as nKg, where n represents magnitude, and kg the unit of mass.

Others define physical magnitude as the measurable quantity of a physical system. It is measured using a standard that has exactly defined said magnitude, and taking as a unit the amount of that property that the standard object has.

The International Office of Weights and Measures through the International Vocabulary of Metrology (VIM) defines magnitude as an attribute of a phenomenon, body or substance, which can be distinguished qualitatively and quantitatively determined.

What are the fundamental magnitudes?

The fundamental quantities, according to the International System of Units (SI) are the following: length, time, mass, intensity of electric current, temperature, quantity of substance (mol) and light intensity. Therefore, there are seven fundamental quantities.

Length

Meter (m). The meter is the distance traveled by light in vacuum in 1 / 299,792,458 seconds. Pattern established in 1883.

Weather

Seconds). It is the duration of 9,192,631,770 periods of radiation corresponding to the transition between the hyperfine levels of the ground state of cesium-133. Pattern established in 1967.

Mass

Kilogram (kg). The kilogram is the mass of a platinum-iridium alloy cylinder deposited with the International Bureau of Weights and Measures. Pattern established in 1887. However, currently its exact value is defined from Planck's constant.

Electric current intensity

Ampere (A). The ampere or ampere is the constant current intensity that, remaining in two parallel conductors, rectilinear, of infinite length, of negligible circular section and located at a distance of one meter from each other in a vacuum, would produce a force equal to 2 · 10 ^-7 newtons per meter of length.

Temperature

Kelvin (K). The kelvin is the fraction 1 / 273.16 of the triple point temperature of water.

Amount of substance

Mol (mol). The mole is the amount of a substance in a system that contains as many elemental units as there are atoms in 12 grams of carbon-12.

Light intensity

Candela (cd). The candela is the unit of light in a given direction of a source of monochromatic radiation of frequency 540 · 10 ¹² Hz, and whose energy intensity in that direction is 1/683 watts / steradian.

Which represent?

The length

Length is a measure of a linear dimension, that is, of a straight or curved line. They also refer to length as the side of a body with the greatest extension, without further consideration.

Cartographers consider longitude as the angular distance (degrees, minutes and seconds) of any point on Earth, in relation to the Meridian 0 that passes through the Astronomical Observatory in Greenwich, London.

Length is a fundamental quantity of an extensive type, since it is additive and varies with the extension or size considered. In addition, it is a vector type magnitude because it has a quantity, a direction and a sense. The unit in SI is the meter, but in CGS it is the centimeter.

Weather

Physical magnitude that indicates the duration of events that can vary determining the periods of duration. It is also defined as the period in which an action is performed or an event develops.

It is a physical magnitude of the scalar type, although some point out that it is vector. In both SI and CGS the unit is the second

Mass

Indicates the amount of matter in a substance or a body. It is an extensive fundamental quantity, since it is additive and is influenced by the size of the entity to which it belongs. In addition, it is a fundamental magnitude of the scalar type, since it only indicates quantity, without indicating direction and direction.

In SI the unit of mass is the kilogram. Meanwhile, in the CGS the unit of mass is the gram.

Electric current intensity

The intensity of electric current (I) is defined as the amount of electric charge (Q) that passes through the cross section of a conductor per unit of time (t):

I = Q / t

Charge is mainly carried by electrons in motion. The current intensity (I) is expressed in amperes; the amount of charge (Q) does it in coulombs; and time (t), in seconds. The intensity of current is a physical magnitude of a scalar and intensive type.

Temperature

It is a measure of the amount of heat in a body. Heat is a form of energy that flows in favor of its difference in concentration. Temperature is a fundamental magnitude of the scalar and intensive type.

Absolute zero (0 Kelvin) is the lowest possible temperature. At this temperature the value of the enthalpy and entropy of a frozen ideal gas reaches its minimum value. The 0 kelvin is equivalent to - 273.16 ºC.

Because it is a constant and absolute value, the kelvin is used as a unit of the fundamental magnitude of temperature, relating it to the triple point of water. This is characterized by the solid, liquid and gaseous states of water being in equilibrium.

Amount of substance

The mole is equivalent to 6.022 · 10 ²³ atoms or molecules (Avogadro's number) and is a constant value for all elements and compounds. For this reason, a mole of any substance is said to contain as many elemental units as there are 12 grams of carbon-12.

In 12 grams of carbon-12 there is one mole of the element, since by definition 12 grams of this element is the mass of one mole of it.

Light intensity

Luminous intensity is defined in photometry as the amount of luminous flux emitted by a source per unit solid angle. Steradian is the SI derived unit that measures solid angles. It is the three-dimensional equivalent of the radian.

Luminous intensity is also defined as the light radiated per second in a specific direction, known as radiant intensity. It is defined by the following formula:

IV = Im / sr

Where IV is the luminous intensity, Im the luminous flux, and sr the steradian.

Luminous flux is a measure of perceived light power. The unit of light intensity is the candela, which is traditionally defined as the light intensity produced by a lit candle.

References

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