F is Every subject of study and every field education has some basic quantities that form the foundational basis for that subject. Like every field of study, the Electrical has 4 basic Quantities: Voltage, Current, Resistance and Power. After reading this article, you will be able to develop a clear insight about these quantities.


It is defined as the potential difference between two points.

The concept of voltage can be easily understood by comparing magnetic forces of material with electrical forces. We all are familiar with the simple magnet and its magnetic property by which it attracts some metallic objects towards itself. A magnet has the magnetic force which surrounds its core and it attracts every other object which is placed inside its field. The magnetic forces are strong near the magnet and they begin to weak while we move away from that magnet.

Like a magnetic force, there is a similar force which is named as the Electric force (EF). Like the previous case of magnets, EF is strong at some points, and it is weak at other points. The comparative difference of Electric force between weak and strong points is known as potential difference. Technically the name ‘Voltage’ represents this potential difference which exists between different points.


The flow of charges from one point to another.

Electrical conductors contain a large number of electrons. The application of voltage source (potential difference) across any conductor causes the flow of electrons from lower to the higher terminal.

Two different conventions represent the flow of charges from one point to another.

Conventional Current Flow

In old days the scientists though that flow of charges from positive to the negative terminal is responsible for the current flow. (In real the case is opposite). However, the trend is still followed today and this type of flow is known as conventional current flow.

Electron Current Flow

The flow of electron from -ve to +ve terminals is responsible for the flow of current. This type of flow is known as Electron current flow.


We previously studied that moving electrons are responsible for producing current in any circuit. These moving electrons continuously collide with the static atoms and electrons present in the atom. A quantity resistance represents this opposition offered by static atoms and electrons. In simple words, we can describe the resistance as an opposition force which tends to reduce the current flowing through any circuit.

Resistors are the practical components which provide resistance.


The ability of anybody to do work is known as Power.

In Electrical terms, it can be defined as the transfer of energy per unit time. Mathematically we can explain it as the current times voltage.

P = VI

The above discussion along with the units of quantities can be summarised in this graphic:


Power, Current, Voltage and Resistance are the four basic Electrical quantities that help us to understand What exactly Electrical is and what are we going to study.