What is electrical current ? - Definitions of electrical current | Electrical current measured in |Conventional current and direction of electron flow

Before discussing about What is Electrical current ? First we have to discuss about electrical charge
so lets get short discussion about Electron theory ,

Fig 01

Electric charge and energy form the two most fundamental electrical quantities. We know that an atom consists of electrons, protons and neutrons. Each electron has negative(-) charge, each proton has a positive (+) charge while an atom, the number of electrons is equal to the number of protons.

The electrons may be added to or taken away from an atom.This causes the atom to be charged negatively or positively.

If the atom has a electron in excess this electron needed to remove from atom ; called a positive ion.

If an electron is added to an atom, it attains a negative charge; called a negative ion.

The basic unit of charge is charge of an electron. The unit of charge in the international system of units is the Coulomb (C).

An electron has a negative charge of 1.601x10⁻¹⁹ Coulomb.

The charge may be at rest or be in motion. A charge in motion constitutes an electric current.

Bound and Free electrons

Electrons are revolve around Nucleus in their orbits as shown in fig 1. Every orbit can accommodate maximum 2n² number of electron. where n is orbit.

orbit 1 as shown in fig can accommodate 2 electron

orbit 2 can accommodate 8 electron

orbit 3 can accommodate 18 electron

The rule 2n² of is not valid for the outer most shell of a atom. The outer most shell or orbit of a atom contains maximum of 8 electrons.

Electrons in outer most shell or orbit is called Valance electrons .

electrons in inner complete orbit is called bound electrons.this electrons are strongly attached to the nucleus because of strong attractive force.

electrons in outer most shell or orbit is called free electrons. they can move in one atom to other atom easily .

Definitions of electrical current

Basically we can say flow of electrical charge is called electrical current.

exact definition of current is

Electric current is defined as the time rate of change of charge passing through a specified area.

i= dq / dt

i= coulomb / second

where q is charge in coulomb and t is time in second.

The charge is measured in coulombs per time in seconds, so the unit of electric current is coulomb/Sec (C/s) or amperes (A). The amperes is the SI unit of the conductor. The I is the symbolic representation of the current.

It measured by an instrument called Ammeter.

If one coulomb of charge passes thorough a conductor in one second than this current called one ampere.

Flow of current and number of electrons

i= dq / dt

i= coulomb / second

One coulomb per second is called one ampere
An electron has a negative charge of 1.601x10⁻¹⁹ Coulomb.

therefor 1 coulomb = 1 / 1.601x10⁻¹⁹ = 6.242 x 10¹⁸ electrons.

so we can say if one ampere of current if flow. There is 6.242 x 10¹⁸ electrons are flow through conductor per second.

Multiples of the ampere we use the following expressions.

1 kilo-ampere = 1 kA = 1000 A = 1 x 10³A
1 milli-ampere = 1 mA = 1/1000 A = 1 x 10⁻³A
1 micro-ampere = 1 μA = 1/1000000 A = 1 x 10⁻⁶A

Conventional current and direction of electron flow

In above fig conductor X Y connected to the battery X connected to positive terminal p and Y connected to negative terminal q. Resistance R is connected to limit current.

Electron have negative charge so they attracted to positive terminal of battery. Electrons flow towards the positive terminal of battery and enter in it. now form negative terminal that same number of electrons are flow towards the conductor.

Before invention of electron theory , assumption is made that current is flow due to positive electrons. and current flow form negative terminal to conductor and than enter to positive terminal of battery.

After invention of electron theory , according to this theory electron flow negative terminal to positive terminal .

There is so confusion regarding direction of current and flow of electron.To solve this problem

we accept that

Current flow from positive terminal of battery to conductor and enter to negative terminal of battery. this current is called Conventional current. and flow of electron is in opposite direction of current.

All network analysis problem are solve on basis of conventional current.

This is my view on what is current ? and definition of current after my research on it.

Thank you.

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