Electric current



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

The intensity of electric current 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 colombium passes through a section of the conductor in 1 second.

How is the intensity of an electric current measured?

The galvanometer is the instrument used to measure the intensity of the electric current. For a correct measurement, the galvanometer must be placed in series with the conductor whose intensity is to be measured.

AmperageThe unit of measurement for intensity is Ampere A in the International System of Units. If the galvanometer is calibrated in amps it is called an ammeter.

Amps should not be confused with amp-hours. The ampere-hour is a unit that measures the amount of electrical charge that flows through a storage device if it supplies a current of 1 ampere for 1 hour. An ampere-hour equals 3,600 coulombs.

How is a current intensity generated?

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

The movement of these electrical charges is carried out 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.

Two types of electric current can exist in an electrical circuit :

  • DC (DC).
  • Alternating current ( AC).

What is the difference between current intensity and voltage?

Current and voltage are two different but related aspects of electricity. Voltage is the difference in electrical potential between two points, while current is the flow of electrical charges (or the  amount of electrical charge) through a conductive material .

Along with resistance, they form Ohm's law that relates the three variables together. Ohm's Law states that the voltage between two points of an element is equivalent to the resistance of the element multiplied by the current that flows through it.

To better understand what voltage is and what intensity is, we will explain it less by means of an example :

Let's say you have two water tanks. One is half empty while the other is full. The difference in water levels in the two tanks is similar to a voltage difference. And like water when given a path, the electrical potential would move from the point of greatest potential to the point of least potential until the two levels are equal.

What is the 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 bone. The current density is designated by the symbol J. In the definition of current density it is assumed that current flows uniformly through the conductor cross section.


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

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

What is the impediment?

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 the maximum values ​​or the effective values ​​of voltage and current.

In the international measurement system, the unit of measurement for 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.

valoración: 3 - votos 1

Last review: March 29, 2020