Electric current

Current Intensity

Current Intensity

Current intensity is the electrical charge that a section of the conductor passes through a unit of time. The concept of electric current intensity is one of the first and most fundamental concepts of the study of electricity.

The unit of measurement of the current intensity is the A amp in the International System of Units. On the other hand, the instrument used to measure the intensity of the electric current is the galvanometer placed in series with the conductor whose intensity is to be measured. If the galvanometer is calibrated in amps it is called an ammeter.

The electric current intensity is given by the following formula:

I = Q / t


I: Intensity expressed in Amps (A) 
Q: Electric charge expressed in Coulombs (C) 
t: Time expressed in seconds (sec.)

With this definition, we can say that an electric current has an intensity of 1 amp when a load of 1 Colombian passes through a section of the conductor in 1 second.

How is a current intensity generated?

At the moment when the ends of the same conductor are connected to two electric fields of different potential, the electrons present in the conductor experience forces of attraction and repulsion. These electrical forces cause electrons to move.

The movement of these electric charges is done with a certain speed, so that if we consider any section located at a point between the two extremes, a certain number of electrons per second will pass through it, that is, a certain amount of electricity per second .

That amount of electricity per second is called the intensity of the electric current expressed in amps.

Current density

Another concept related to the intensity of electric current is the current density. With the current density we can express the average current per unit of a conductor's artery. The current density is designated by the symbol J. In the definition of current density it is assumed that the current flows uniformly through the cross-section of the conductor.

J = I / S

J is measured in units of the International System in A / m2 (amps per square meter) but it is often expressed in A / mm2 since, obviously, being a conductor section, it is more manageable to perform the measurement in square millimeters.

Current density is an important value when calculating the section of a conductor through which a certain electric current has to circulate.


The impediment is the magnitude that determines the correspondence between the voltage and the intensity of the electric current. It is a magnitude that expresses the relationship between voltage and intensity for a current, in a given time. Its module (sometimes called improperly impedance) establishes the relationship between maximum values ​​or effective voltage and current values.

In the international system of measurements, the unit of measure of impedance is Ohm.

The impediment is one of the most important characteristics of a cable as well as for all the elements of the network, which indicates the resistance to alternating current between wires that the cable offers at different frequencies.

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Last review: November 15, 2019