The Fundamental and derived variables Are the physical magnitudes that allow to express any quantity or measurement of the bodies.
Experimentation is a fundamental aspect of the physical And other physical sciences. Theories and other hypotheses are verified and established as scientific truth through realized experiments.
Measurements are an integral part of experiments, where the magnitudes and relationships between different physical quantities are used to verify the truth of the theory or hypotheses.
Types of magnitudes: fundamental and derived
Key figures
In each system of units is defined a set of fundamental units whose physical quantities are called fundamental magnitudes.
The fundamental units are defined independently and often the quantities are directly measurable in a physical system.
In general, a system of units requires three mechanical units (mass, length and time). An electrical unit is also required.
The magnitudes that do not depend on any other physical quantity for their measurement are known as fundamental quantities, do not depend on any other quantity that can be expressed. There are a total of seven fundamental magnitudes:
1- Mass: kilogram (kg)
It is defined by the mass of a platinum-iridium cylinder prototype maintained at the International Bureau of Weights and Measures in Paris, France.
Copies of this cylinder are kept by many countries that use them to standardize and compare weights.
2- Length: meter (m)
It is defined as the length of the path traveled by light in a range of exactly 1/299792458 seconds.
3- Time: second (s)
According to the International System of Units, it is the time of 192,631,770 periods of oscillations of light emitted by a cesium -133 atoms corresponds to the transition between two hyperfine levels of the ground state. This is determined by the use of high precision atomic clocks.
4- Electrical current: Ampere (A)
It measures the intensity of electric current. It is defined by the constant current that if it flows in two parallel straight conductors of infinite length and negligible section flows, when it is to 1 meter of distance in the vacuum, produces a force equal to 2 × 10-7 Newton by meter of length between These drivers.
While it may seem that the electric charge should have been used as the base unit, the current measurement is much easier and therefore it is chosen as the standard base unit.
5- Temperature: kelvin (K)
According to the International System of Units, the Kelvin is exactly 1 / 273.16 of the thermodynamic temperature of the triple point of water.
The triple point of the water is a temperature and a fixed pressure in which the Solid, liquid and gaseous states at the same time.
6- Light intensity: candela (cd)
It measures the light intensity of a source emitting radiation of a constant frequency of 540 × 1012 Hz with a radiant intensity of 1/683 watts per sterane in any given direction.
7-mol (mol)
The mole is the amount of substance containing as many entities as atoms in 0.012 kg of carbon-12.
For example: the fundamental mass magnitude, can be measured directly using a scale and therefore, does not depend on another magnitude.
Derived magnitudes
The derived quantities are formed by the product of the powers of the fundamental units. In other words, these quantities derive from the use of the fundamental units.
These units are not defined independently, as they depend on the definition of other units. The quantities associated with the derived units are called derived quantities.
For example, consider the vector quantity of velocity. By measuring the distance traveled by an object and the time taken, the average speed of the object can be determined. Therefore, velocity is a derived variable.
The electric charge is also a derivative quantity given by the product of the current flow and the time taken.
Except for the 7 fundamental quantities mentioned above, all other magnitudes are derived. Some examples of derived magnitudes are:
1- Work unit: joule or July (J)
It is the work done when the point of application of the force of a newton (1 N) moves at a distance of one meter (1 m) in the direction of the force.
2- Strength: newton (N)
It is that force which, when applied to a body with a mass of one kilogram (1 kg), gives an acceleration of one meter per second squared (1 m x s 2 ).
3- Pressure: pascal (Pa)
It is the pressure that results when a force of one Newton (1 N) is applied uniformly and perpendicularly to a surface of 1 square meter (1 m 2 ).
4- Power: watt or watt (W)
It is the power that generates the energy production at the rate of one joule per second (1 J x s).
5- Electric charge: coulomb or coulomb (C)
It is the amount of electric charge carried in one second (1 s) by a current of an ampere (1 A).
6- Electrical potential: volt (V)
It is the potential difference between two points of a conduction wire carrying a constant current of an ampere (1 A), when the power dissipated between these points is one watt (1 W).
7- Electrical resistance: ohm or ohm (Ω)
Measures electrical resistance. Specifically, that present between two points of a conductor when a constant potential difference of a volt (1 V), applied between these two points, produces a current of one ampere (1 A), the conductor being the source of no electromotive force .
8- Frequency: hertz or hertz (Hz)
It is the frequency of a periodic phenomenon whose period is one second (1 s).
References
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