Physical quantities are all those measurable and quantifiable characteristics that physical bodies may have, which can be divided into two types, the fundamental quantities that can be obtained independently, and the derivatives that depend on the previous ones.
The physical sciences depend for the most part on experiments, because it is a science in which hypotheses need tests to certify the information, in which all magnitudes make an appearance, since they are very common in these experiments.
In physical terms, the magnitude is any property that a substance, material or physical body possesses that is quantifiable and measurable, such as mass, length or volume, by which it is possible to obtain the necessary data from them. .
For best results, we proceed to measure, which consists of compare the magnitudes with other similar ones, which are usually called units, which gives better results to the experiment.
Units are quantities that are used as a guide to measure other quantities of the same type, such as when weighing an object which is said to have two kilograms, which has twice the unit taken as a standard, which is the kilogram .
In times before 1960, different magnitudes were used throughout the entire planet, so in that year, at the eleventh meeting of the general conference of weights and measures in Paris, what would be the fundamental magnitudes for the entire world were named. world, no exceptions.
First, the fundamental quantities were defined, since they are independent, to later decide which would be the derivatives, which depend on the previous ones to be calculated or measured.
Now that it is recognized that they are the magnitudes, what it is to measure, what it is for and how a measurement is made, and that they are the units, it is much easier to understand what the fundamental and derived magnitudes would be, in turn how to use them.
What are the fundamental quantities?
These are the conventional and main units of measurement of properties of a physical body, which when combined create the derived quantities. These magnitudes were chosen by the international system of units or better known by SI, which gave 7 units that are mass, length, temperature, time, light intensity, amount of substance and current intensity, each having one of these is its unit of comparison and its own symbol that characterizes it.
Mass
It is a general property of matter, which measures the amount of matter that a body itself contains, using the kilogram as the unit that has the Kg as symbol, this is obtained with its inertia, since it is the acceleration that it exerts a force on him.
The length
This is obtained by having a brief notion of the distance of the object, which is a metric concept, which has been defined by knowing the distance of a geometric body, which should not be confused, because the length will always be greater than the given distance, that's a one-dimensional measurement.
According to Albert Einstein, length is not a defined property, because all physical bodies are measurable, and depending on the observer, different results could be obtained.
Weather
It is a physical property with which the events that occur are determined, which can be separated into past, future and a third that is none of the above, which was called present. Thanks to this, events can be ordered and even their duration determined.
The unit of this magnitude is the second, which is symbolized by the s, the capital letter or the abbreviation seg should not be used because its respective and corresponding symbol is the one that was shown in the first place.
Temperature
It is a magnitude based on scales defined by the internal energy of a thermodynamic body, when it is spoken in physical terms, in turn it is also known as that property measurable through a thermometer, which is usually heat.
The temperature units that the international system of units defined as the fundamental one is the Kelvin symbolized by K, although in scientific experiments several temperature units are usually used, the most popular being the Celsius or degrees centigrade, and the Fahrenheit in the USA
Luminous intensity
It is defined as the amount of luminous flux that a body or physical substance possesses for each unit of solid angle, its unit is the candela symbolized by the Cd granted by the international system of units.
A point light source is called one that emits its light energy in all directions equally, such as lamps, instead of those whose luminescence varies depending on the angle of the direction considered and its normal direction, to which they are called the Lambert reflective surface.
Amount of substance
It is defined as the number of entities present in a substance or physical body, depending on the unit of quantity of substance chosen, it could affect the constant of proportionality, which has the mole as the default unit, which is defined as the amount of substance that have a physical body.
Amperage
This is due to the movement of charges in it, which are usually electrons, which is the flow of electric current that a material can travel, this is also called flow, which is the amount of charge per unit of time. Its units the ampere symbolized by A.
The instrument with which this unit is quantified and measured is the galvanometer, which when calibrated in amperes is known as an ammeter.
For these magnitudes there is also the cegesimal system of units which can be used to measure mass, length and time, each having its respective cegesimal unit that will be shown below.
- Mass: for this the gram (g) is used
- Length: centimeters (cm) are used to measure this property
- Time: when measuring a certain quantity of this magnitude, the second (s) is used
What are the derived quantities?
These are the result of the combination of the fundamental magnitudes, giving as results these derivatives, among which there are several, but the most common are energy, force, acceleration, density, volume and frequency.
To obtain these quantities, it is necessary to combine two or more fundamental quantities, such as, for example, if you want to obtain force, you must multiply the mass by the length and then divide it twice by time.
These magnitudes also have their respective units, which are the following:
- Force: Newton (N) is used
- Energy: for this the Julio (J) is used
- Acceleration: the meter over second squared (m / s2) is used
- Volume: cubic meter (m3) is used
- Density: In this the kilogram per cubic meter (kg / m3) is used
- Frequency: for this the hertz (Hz) is used
There are many of these, since even more than two fundamental quantities can be combined, which can result in properties such as molar volume, pressure, electric charge, magnetic flux, inductance, among many others.