Electric current

Laws of Electricity, Concepts and Descriptions

Laws of electricity, concepts and descriptions

Electricity is the movement of electrical charges that circulate through a conductor. This movement is carried out according to certain physical properties. These properties are collected in a series of laws and theorems that scientists have developed throughout history.

The most important laws and theorems related to electrical energy are:

Coulomb's Law

Coulomb's law states that the electric force of two charged objects is inversely proportional to the square of the distance between them. Coulomb's law also says that this force is directly proportional to the product of the charges.

This law was first introduced in 1785 by the physicist Charles-Augustin de Coulomb

Ampère's Law

Ampère's law was developed by the Frenchman André-Marie Ampère in 1831. Ampère's law relates a static magnetic field to the cause that causes it. Later, James Clerk Maxwell corrected it and it became part of Maxwell's equations.

Ampère's law indicates that the circulation of the intensity of the magnetic field in a closed contour is proportional to the electric current that flows in that contour.

Ohm's Law

Ohm's law states that the intensity of electric current flowing from a conductor connecting two points is directly proportional to the voltage between the two points and inversely proportional to the electrical resistance of the conductor.

Ohm's law manages to describe with great precision the behavior of almost all electrically conductive materials. However, there are some conductive materials that do not follow this law. These are called non-ohmic conductive materials.

The law owes its name to the German physicist George Ohm. In 1827, George Ohm described the currents and voltages that occur in simple electrical circuits. In his honor, the resistance is expressed in Ohms (ω).

Faraday's Law

Faraday's law of electromagnetic induction is a basic law of electromagnetism, with:

  • a transformer

  • an inductance element

  • a plurality of generator operation closely.

The law states that:

The magnitude of the induced electromotive force in any closed circuit is equal to the rate of change of the magnetic flux through the circuit.

This law was discovered by Michael Faraday in 1831. Joseph Henry discovered this law before Faraday in an independent study in 1830, but he did not publish this discovery. Therefore, this law is called Faraday's law.

Traditionally, there are two ways to change the magnetic flux through the circuit. As for the induced electromotive force, what changes is your own electric field, like changing the current that the field generates (like a transformer). As for the electromotive driving force, what changes is the movement of all or part of the circuit in the magnetic field, as in a generator of the same polarity.

Kirchhoff's Current Law (kirchhoff's First Law):

Kirchhoff's law of currents applies to a current that passes through a node of a closed electrical circuit at steady state.

According to Kirchhoff's law, the algebraic sum of the currents entering any node in an electrical circuit (with a different sign if they enter or leave) is zero.

Kirchhoff's Stress Law (kirchhoff's Second Law)

In general, Kirchhoff's stress law states that the algebraic sum of the voltage drops acting between the pairs of points in space that form any closed (oriented) sequence is equal to zero.

In the simplest formulation, the law says that the algebraic sum of the electric potential along a closed line (with the appropriate sign depending on the direction of displacement of the mesh) is equal to zero.

Thévenin's Theorem

Thévenin's theorem refers to any linear circuit with only voltage and current sources and resistors. The theorem states that if points A and B are available, it is equivalent to a single voltage source V and a single resistor R in series with it.

Bernard Thévenet's theorem is the statement that any source can be replaced in an equivalent way by an ideal voltage source connected in series and internal resistance.

This theorem is a dual statement of Norton's theorem about the equivalent replacement of an arbitrary circuit with an ideal current source and a resistor connected in parallel.

In other words, the current in any resistor Zn connected to any circuit is equal to the current in the same resistor Zn connected to an ideal voltage source with a voltage equal to the open circuit voltage of the circuit. Furthermore, it has an internal resistance Zi equal to the total resistance of the "closed part" of the circuit. This resistance is determined by the Zn terminal side provided that all the sources within the circuit are replaced by impedances equal to the internal impedances of these sources.

Norton's Theorem

In the field of electrical circuits, Norton's theorem states that any linear circuit, no matter how complex, seen from two nodes A and B is equivalent to a real current generator consisting of an ideal current generator in parallel with a endurance. The equivalence is limited to the voltage and current at nodes A and B.

Norton's theorem is an extension of Thévenin's theorem and was obtained in 1926 by two different people at the same time:

  • Hans Ferdinand Mayer (1895-1980), a Hause-Siemens researcher

  • Edward Lawry Norton (1898-1983), a Bell laboratory. engineer.

Only Mayer published his work, but Norton released his work through an internal Bell Laboratories technical report.

Superposition Theorem

The superposition theorem states that in a linear circuit with more than one independent source, the effect of all sources on an impedance is the sum of the effects of each source independently, replacing other voltage sources with a short circuit and replacing all all other current sources with an open circuit.


Published: September 12, 2021
Last review: September 12, 2021