# Electric current

Electric current is one of the most basic term in electrical engineering. It is the flow of electric charge in a closed circuit.

In simple, when the valence electrons of a conductor start moving in the same direction the current is said to be flow through that conductor.

Actually electric current define the rate of flow of charge electric charge through a conducting medium with respect to timeCurrent in amp tell us how many electrons are passing through a specific area of conductor per second.

## Concept of electric current

Atom is a material having large number free electrons. These electrons are continuously in motion but the motion is a random therefore there is no flow in a given direction. When electric pressure is apply, all the free electrons start moving in same direction i.e. from negative to positive. This direct flow of electron is called electric current. Hence the emf induced in a closed circuit cause electrical current to flow in the closed circuit.

Now the question is why electrons moves toward the positive terminal?
Electrons are negatively charged particles therefore electrons are attract by positive terminal and repel by the negative terminal. As the direction of flow of conventional current is opposite to the direction of flow of electrons. Which means  conventional current flow from positive terminal to negative terminal.

## Types of electric current

There are two types of electric current
1. AC (Alternating Current)
2. DC (Direct Current)

1. 1.Alternating currentis the current which reverses its direction after every half cycle. It means that in AC flow of electric charge changes its direction continuously after regular interval of time. There are positive and negative sides as shown in figure.
2. 2. Direct currentis the current which flow only in one direction. In DC the flow of electric charge of electrons is only in one direction. There is only positive side as shown in figure.

## Measurement of electric current

There is a device which is used to measure the electric current and the device name is ammeter. An ammeter is connected in series with load to measure the electric current.

Suppose Q is the charge flow through any specific area of the conductor in a time t second, then

Electric current  = charge/time

Hence electric current is measured by the time rate of flow of charge through the conductor.

Unit of Electric Current
The unit of electric current is Ampere.

1 ampere = one column/one second

The current flow through a specific area of a conductor is said to be one ampere when one coulombs of charge flow through it in one second.

1 Coulomb = charge on 6.25 × 10^18 electrons

Therefore, when 6.25 × 10^18 electrons flow through a specific area of conductor in one second, the quantity of current is said to be one ampere.