Basic Electrical Engineering Laws

Basic Electrical Engineering Laws

In this article, we will discuss various Basic Electrical Engineering Laws.

Ohm’s Law

Ohm’s law gives a relation between voltage (V) and current (I).

Statement: “The electric current flowing through any conductor is directly proportional to the potential difference (voltage) between the terminals of a conductor (Assuming the physical condition of the conductor remains unchanged).”

According to ohm’s law;

    \[ V \propto I \]

    \[ Voltage \, V = \frac{I}{R} \, Volt \]

Kirchhoff’s Law

German physicist Gustav Kirchhoff described Kirchhoff’s circuit law.

Kirchhoff’s Current Law

This law is also known as Kirchhoff’s first law or Kirchhoff’s Point rule.

Statement: “The sum of current flowing into the node is equal to the sum of current flowing out of that node.”

In other words, “the algebraic sum of currents in a circuit conductor meeting at a node is zero.”

    \[ \sum_{k=1}^n I_k = 0 \]

Where n is the total number of branches.

Kirchhoff’s Voltage Law

This law is also known as Kirchhoff’s second law or Kirchhoff’s Loop (mesh) rule.

Statement: “In a close loop, the directed sum of potential difference (voltage) is zero.”

    \[ \sum_{k=1}^n V_k  = 0 \]

Coulomb’s Law

Coulomb’s law was discovered by Charles-Augustin de Coulomb in 1785.

Coulomb’s First Law

Statement: It states that like-charged objects (bodies or particles) repel each other and, unlike charged objects, attract each other.

Coulomb’s Second Law

Statement: It states that the force attraction and repulsion between two electrically charged objects is directly proportional to the magnitude of their charge and inversely proportional to the square of the distance between them.

    \[ F \propto Q_1 Q_2 \, and \, F \propto \frac{1}{d^2} \]

    \[ F \propto \frac{Q_1 Q_2}{d^2} \]

    \[ F = k \frac{Q_1 Q_2}{d^2} \]

Faraday’s Electromagnetic Induction Law

Faraday’s electromagnetic induction law is simply known as Faraday’s law. This law predicts how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF).

This law is a fundamental operating principle of transformers, inductors, and many electrical machines.

Statement: “The electromotive force around the close path is equal to the negative of the time rate of change of the magnetic flux enclosed by the path.”

    \[ \iint_{\sum(t)} B(t) dA \]

Faraday’s law states that the emf is also given by the rate of change of the magnetic flux;

    \[ E = - \frac{d\phi}{dt} \]

Lenz’s law gives the direction of the EMF.

Lenz’s Law

This law was named after the physicist Emil Lenz in 1834.

Statement: “The direction of electric current induced in a conductor by a changing magnetic field is such that the magnetic field created by induced current opposes changes in a main magnetic field.”

The negative sign in faraday’s law represents by the Lenz law.

Gauss’s Law

Carl Friedrich Gauss introduced the Gauss’s law in 1835. This law is also known as Gauss’s flux theorem.

This law gives a relation between electric charge to the resulting electric field.

According to Gauss’s law, the flux of the electric field out of an arbitrary closed surface is proportional to the electric charge enclosed by the surface, irrespective of how that charge is distributed.

Statement: “The net electric flux through any hypothetical closed surface is equal to \frac{1}{\epsilon_0} times the net electric charge within that closed surface.”

Gauss’s law is expressed as;

    \[ \phi_E = \frac{Q}{\epsilon_0} \]


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