## Monday, 17 February 2014

### Basics Of Electric Current - High School Physics Tutorial

Electric Current is the flow of electrons in a substance from it’s one point to another in other words Electric Current is the rate at which the charges or electrons flows through a particular surface or point in a substance for eg. The current in a wire is the rate at which the charges carrying electrons passes through the cross sectional surface of the wire.

Electromotive force (EMF)
Voltage Source and Current Source
Body Or Chassis Ground in Electronic Circuits

The anatomy of a conductor and flow of current:A conductor is usually made up of a lot of molecules piled one over another , and the molecules are collection of atoms.

A atom contains two charged particles in it namely Electrons and Protons which have the charges as following:

Proton: Positive   coulombs.

Electron: Negative   coulombs.

When the surplus of electrons is supplied from one end of a wire or any conductor then the electron knocks out an electron from one of the atoms and the knocked out electron then knocks out electron from another atom , the process continues and an extra electron is knocked out from the end point of the conductor this process is called of flow of electrons or Flow of charges which is known as the flow of current.

Formula for Electric Current:

Electric current is denoted by the symbol .

As per the definition of the electric current: “The rate of flow of charges” it can be mathematically denoted as:

Where q = The total charge flowing through the conductor.

And t = Total time taken for the flow of ‘q’ charges.
Unit:

The S.I. unit of electric current is Ampere and is denoted by

And mathematically when one coulomb of charges (  Atoms) flow through the conductor per unit time ;or per second; then the electric current flowing the conductor is said to be of One Ampere.

Conventional Direction of Electric Current:

As discussed above the Electron have a negative electric charge and it is the electron whose flow in a circuit or conductor is responsible for the current , Thus it is the normal convention to take the direction of electric current as if it is flowing opposite to the direction of flow of electrons to make the calculated electric current a positive value.

So the flow of current in a circuit is in the exact opposite direction to the direction of flow of charges.

Direct and Alternating Current:

Direct current ( DC) is the current where the flow of electric charges is unidirectional in nature. In DC the current flows continuously toward a same direction. A DC current is provided by devices like Batteries , Solar cell etc.

Opposite to DC alternating current is the current where the flow of electric charges is bidirectional in nature. In AC the current flow is in one direction for a instance and in another instance the flow of current is reversed ; the process continues until the current is provided. The rate at which the direction of flow of current changes in an AC is known as it’s frequency. AC current is used to transmit signals for eg. radio signals.