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## Introduction

Inside a material are millions of atoms. These atoms have several electrons revolving around the nucleus and none of these electrons are at rest. Under certain conditions, it is possible to get these electrons to flow across the material in a guided manner. This flow of charges is known as electric current. The branch of physics that deals with the study of current and electricity began with the invention of batteries by Alessandro Voldo.

Today, the world is heavily dependent on electricity as a form of energy and our lives would become impossible without it. This article discusses current and electricity from a physicist’s perspective.

## Electric Current

Current is the flow of charges across a given conducting path and its direction is conventionally taken to be opposite to the direction of movement of electrons. This means that current flows from a region of lower voltage to a region of higher voltage. In practice, this voltage difference is generally created using a battery, which gives rise to the movement of electrons inside the material. Electric current is defined as the amount of charge flowing through a given cross-section in unit time. Mathematically,

Current is not directly dependent on the size of the cross-section through which charges are flowing. Rather, it is only the amount of charge and the time taken that makes a difference. In general, since the flow of charges isn’t a constant value, we can define the average current as:

And the instantaneous value of current may be found by taking the limiting case of the above equation. That is,

The SI unit of measuring current is the Ampere, which is defined as the flow of 1 Coulomb charge in 1 second.

## Direction Of Electric Current

The direction of electric current is represented by arrows in the circuit. When a battery is attached to a circuit, electrons flow from the negative to the positive terminal. And conventionally, the direction of current is taken as opposite to the direction of electron flow, i.e., from the positive to the negative terminal.