Electrical Basics. Article:

What is Current. In which direction does current flows.


Definition of Current.

Current is the flow of electrons in the same direction. When electrons are randomly moving in different directions they is no current and also for electrons to flow there is a need of a closed circuit.

A circuit in general, is a paths in which electrons follow when flowing. A circuit can be Open or Closed.

A closed Circuit.

A closed circuit is when there is a complete connection between circuit components starting from the source e.g a battery, circuit components and back to the source, all switches in ON position.

Switches we use at home, in industries they just close or open the circuit. The following diagram shows a closed circuit, a switch in On position.

closed circuit

An Open Circuit.

An open circuit is when there is a break in a circuit, it can be due to a fault or a switch in OFF position. The following diagram shows an open circuit, a switch in Off position.

open circuit

Current is said, flows in opposite direction with electrons, this seems confusing as in the definition above we said current is the flow of electrons. Don't worry, this is so because of the two discoveries which took place in the early discovery of Electricity.

The first discovery of current took place in the 17th century by Benjamin Franklin - a Scientist. He discovered that they is something which flow inside conductors which he called Current.

He goes forward saying that this current is due to electric fluid flowing inside conductors in the same direction. The electric field was said flows from the positive to the negative.

In the 19th century J.J Thompson a physicist discovered electrons, which he said are the one which cause current or which flows.

He said they flow from negative to positive opposing the first discovery of electric fluid. After the discovery of electrons it was then realised that it is not electric fluid which cause current but these are electrons.

Before the descovery of electrons, scientists in the 17th century decided that current flows from positive to negative following the first discovery and after the discovery of electrons it was then difficult to change the direction because most textbooks where written and electrical symbols of components like diodes were designed following the first direction.

Till today the flow of current from positive to negative is accepted as the general direction of flow of current but it is nothing to do with electrons.

They are two terms which are now used to make a better understanding of current, which are Conventional current and Electron current flow.

Conventional current is current which flows from positive to negative following the first theory and Electron current flow is current which flows from negative to positive following the second theory.

Both two currents seems important since when doing calculations in electrical, it is easy to do calculations using Conventional current since you will be using positive numbers mostly and also electron current flow anables a better understanding on how electronic components works such as diodes, transistors e.t.c.

They are two types of current which are Direct Current and Alternating Current

Direct Current.

Direct Current is a type of current in which electrons flows in only one direction due to stationery position of negative and positive polarities. Direct current is produced by solar panel dc generators.

Alternating Current.

It is a type of current in which electrons changes direction of flow, flowing back and forth due to exchanging of positions between the negative and positive polarities.

Since electrons always flows from negative to positive, when polarities exchange positions they also alternate the direction of flow so that they continue flowing towards the positive polarity.

The exchange of positions between two polarities can be done by moving the magnetic field across a conductor. This type of current is produced by AC generators.

How current is measured.

Current is measured in amperes using an instrument called an Ammeter. One ampare is equivalent to 6 240 000 000 000 000 000 or 6,24 ×10¹⁸ electrons passing through any point within a circuit in every second.

To measure current an Ammeter is put in series with circuit component being measured so that it counts the number of electrons passing through it in every second and display then in ampares on the screen.

The diagram below shows an ammeter connected in series with a circuit lamp.

ammeter measuring current

With the previous information on how current is measured, we can also define Current as the rate of flow of electric charge since we saw that the Ammeter counts the number of electrons passing through it in every second.