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on video What is CURRENT– electric current explained, electricity basics

 



Electric current is one of the most basic concepts that exists within electrical and electronic science - electric current is at the core of the science of electricity.


Whether it is an electrical heater, a large electrical grid system, a mobile phone, computer, remote sensor node or whatever, the concept of electrical current is central to its operation.


However current as such cannot normally be seen, although its effects can be seen, heard and felt all the time, and as a result it is sometimes difficult to gain a view of what it really is.


Lightning strike is an impressive show of electrical current flow

Lightning strike is an impressive show of electrical current flow

Photo taken from top of the Petronas Towers in Kuala Lumpur, Malaysia

Electrical current definition

Electric current definition:

An electric current is a flow of electric charge in a circuit. More specifically, the electric current is the rate of charge flow past a given point in an electric circuit. The charge can be negatively charged electrons or positive charge carriers including protons, positive ions or holes.


The magnitude of the electric current is measured in coulombs per second, the common unit for this being the ampere or amp which is designated by the letter 'A'.



The ampere or amp is widely used within electrical and electronic technology along with the multipliers like milliamp (0.001A), microamp (0.000001A), and so forth.



Read more about. . . . the Ampere, the unit of current.


Current flow in a circuit is normally designated by the letter 'I', and this letter is used in equations like Ohms law where V=I⋅R.


What is electric current: the basics

The basic concept of current is that it is the movement of electrons within a substance. Electrons are minute particles that exist as part of the molecular structure of materials. Sometimes these electrons are held tightly within the molecules and other times they are held loosely and they are able to move around the structure relatively freely.


One very important point to note about the electrons is that they are charged particles - they carry a negative charge. If they move then an amount of charge moves and this is called current.


It is also worth noting that the number of electrons that able to move governs the ability of a particular substance to conduct electricity. Some materials allow current to move better than others.


The motion of the free electrons is normally very haphazard - it is random - as many electrons move in one direction as in another and as a result there is no overall movement of charge.


Random electron movement in a conductor with free electrons - sum total provides zero current flow

Random electron movement in a conductor with free electrons

If a force acts on the electrons to move them in a particular direction, then they will all drift in the same direction, although still in a somewhat haphazard fashion, but there is an overall movement in one direction.


The force that acts on electrons is called electromotive force, or EMF, and its quantity is voltage measured in volts.


Electron flow (current) under the action of applied electro-motive force

Electron flow under the action of applied electro-motive force

To gain a little more understanding about what current is and how it acts in a conductor, it can be compared to water flow in a pipe. There are limitations to this comparison, but it serves as a very basic illustration of current and current flow.


The current can be considered to be like water flowing through a pipe. When pressure is placed on one end it forces the water to move in one direction and flow through the pipe. The amount of water flow is proportional to the pressure placed on the end. The pressure or force placed on the end can be likened to the electro-motive force.


When the pressure is applied to the pipe, or the water is allowed to flow as a result of a tap being opened, then the water flows virtually instantaneously. The same is true for the electrical current.


To gain an idea of the flow of electrons, it takes 6.24 billion, billion electrons per second to flow for a current of one ampere.


Conventional current and electron flow

There is often a lot of misunderstanding about conventional current flow and electron flow. This can be a little confusing at first but it is really quite straightforward.


The particles that carry charge along conductors are free electrons. The electric field direction within a circuit is by definition the direction that positive test charges are pushed. Thus, these negatively charged electrons move in the direction opposite the electric field.


Electron and conventional current flow

Electron and conventional current flow

This came about because the initial investigations in static and dynamic electric currents was based upon what we would now call positive charge carriers. This meant that then early convention for the direction of an electric current was established as the direction that positi



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