In our house there are several electrical and electronic devices, which require different electrical quantities such as electrical voltage, electrical current, electrical resistance and electrical power. In this article we decided to approach one of the main electrical quantities, which is the electric current, in order to show the main characteristics of the electric current.
What is Electric Current?
All substances, gaseous, liquid or solid, are made up of small particles invisible to the human eye, called atoms. The atom is basically divided into two parts, which is the nucleus and the electrosphere. In the nucleus is where protons and neutrons are located, the proton has a positive charge and the neutron has no electrical charge. In the electrosphere is where the electrons that have negative shits are located.
In the existing electrical conductor’s free electrons that are in constant disordered movement. For free electrons to move in an orderly manner in electrical conductors, it is necessary to have a force that drives free electrons, and this force is called electrical voltage.
The force caused by the electrical voltage causes the free electrons to move in an orderly fashion, thus forming an electron current that is called an electric current, represented by the letter (I).
The intensity of the electric current is determined by the ratio between the amount of electrical charges, which cross a determined section of a conductor, over a period of time. The unit of measurement given for the intensity of the electric current by the international system of units (SI) is the amp, in honor of the French scientist, André-marie Ampère (1775 – 1836), to represent the electric current we use the letter (A) as symbol. ).
Types of Electric Current
There are two types of electric current, direct current and alternating current. Direct current (DC or DC) is an ordered flow of free electrons in the same direction, remaining constant over time and has defined roles, that is, positive and negative poles, and this type of electrical current is obtained from the battery, battery, power supplies, charger etc.
Alternating electric current (AC or AC – from English alternating current), is the ordered flow of free electrons in a varied direction over time and has no poles defined as indirec current, varying between phase and neutral means to be present in hydroelectric plants, electrical outlets, substations, etc.
Electric Current Direction
Before studying the structure of atoms there was already a definition for electric current as being the direction of the flow of positive charges, so the charges move from the positive pole to the negative pole.
At the beginning of the history of electricity, because they were not aware of the structure of atoms, they did not know that in solid conductors the positive charges are strongly linked to the nuclei of the atoms, therefore, in solid conductors there can be no positive charge flow.
However, when subatomic physics discovered this fact, the definition for electric current as a flow of positive charges was already widely used in calculations and representations for circuit analysis, so this sense is still used today and is called the conventional current sense. electrical. Thus two directions were defined for the electric current, that is, the real sense and the conventional sense, where the real sense is the flow of electrons from the negative pole to the positive pole and the conventional sense is used in calculations for circuit analysis, being that in this case the direction of the electric current goes from the positive pole to the negative pole of the source.
Electric Current in each type of electrical circuit
The electrical circuit is a closed path through which the electric current flows, there are basically three types of circuit, which are: series, parallel and mixed circuit . The electrical current behaves in different ways in each type of electrical circuit, whereas in series circuits the electrical current is the same at all points. In parallel, the electric current is divided between the meshes, and may have different values of electric current, depending on the point of analysis. In the mixed circuit the electric current behaves in both ways, depending on the analyzed grid.
In order to carry out the analysis and calculations on the circuits, laws and formulas were developed over time, for example, ohm’s law , first kirchhoff’s law and current divider.
Ohm’s law is one of the most applied laws in electrical calculations. Ohms’ law is the basis for electrical calculations and involves four electrical quantities, which are: electrical voltage, electrical current, electrical resistance and electrical power . Ohm’s law is very simple, when we have the value of two of these quantities it is possible to find the value of the third variable, for that it is enough to use the appropriate formula, in the case of the electric current we have three formulas that can be used to obtain the value of electric current.
Kirchhoff’s first law
Kirchhoff’s laws are fundamental to perform series, parallel or mixed circuit analysis, as they are directly related to electrical current. Kirchhoff’s first law, also known as the law of currents or the law of nodes, is related to the electric current in a node. Kirchhoff’s first law says that the result of the sum of the electrical currents in a node is always equal to zero, so the node does not accumulate charge.
The node is a point where the current divides having two or more paths to travel in the circuit and the sum of all currents entering a node is equal to the sum of all currents leaving the node.