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# What is charge and electrical current in electrical circuit?

## Charge Particles

While studying electrical engineering, engineer should must be familiar of the basic electrical engineering terms. Charge is also one of the basic and fundamental building block unit of electrical current. One can explain charge definition in simple words as:

“Charge is an electrical property of the atomic particles of which matter consists. It is measure in coulombs (C)”

We study in our basic elementary science that all matters are compose of major building blocks known as atoms. Every atom consists of electrons, protons, and neutrons. The charge on electron is negative, that is equal to 1.602×10^-19 in magnitude. While the charge on proton is same but is positive in magnitude. The presence of both electrons and protons in equal numbers leaves an atom neutrally charged.  There is no charge on neutrons.

We should note the following points about the electrical charge:

1. The Coulomb is the large unit of charge. 1 Coulomb of charge consist of 6.24×10^18 electrons. i.e. (1/1.602×10^-19 ) = 6.24×10^18. That is why, the value of charges are on the order of pC, nC or µC.
2. According to experimental observations, the charges that occur in nature are integral multiples of the electronic charge. i.e. 1e = -1.602×10^-19 C.
3. The law of conservation of charge states that “charge can neither be created nor destroyed but only transferred.” Thus the total sum of electrical charge in a system does not change.

### Coulomb’s Law

Coulomb’s law states that:

“The force of attraction or repulsion between two charge particles is directly proportional to product of their charges and inversely proportional to the square of the distance present between them”

Suppose consider two point charges q2 and q1 that separates by a distance of R in vacuum. The force by q on q2  will be:

Where, K is the proportionality constant.

The value of proportionality constant (Kcan be determine as:

The direction of the charge movement is determine by the property of charge particles. If both are charge particles are of same type, they will repel each other and vice versa.

## Electric Current

We now consider the flow of electric charge. Any movement of charge constitutes an electric current. These charge carriers could be electrons in a vacuum or in metals, holes in a semiconductor or an ions in a solution. When we connects a conducting wire to a battery, the charges within the wire moves. The positive charge particles moves in one direction while the negative charge particles moves in opposite direction. This motion of charge particles creates electric current. Thus, electric current can be defined as:

“Electric current is the time rate of change of charge, measured in Amperes (A)”

It is conventional to take the direction of electric current flow as the movement of positive charges. This conventional current concept was introduced by Benjamin Franklin also known as the inventor of electricity. Although we know that flow of electric current in metallic conductor is due to electron movements which are negatively charged but we have to follow universal convention of electrical current that current flow is due to net positive charges.

#### Related Questions:

At the end of our topic discussion, following few questions related to electrical field arises in students mind. We would try to explain them briefly. Click on the question below to get its answer:

 What is electrical fault current? What is an electrical eddy current? What is meant by electrical stray current? What is electrical current and how is it different from voltage? What is the relationship among electrical power current and voltage? What level of electrical current can kill a human?

If you still have any question in your mind, feel free to it with us. We will try to response back as soon as possible.

### One comment

1. Awesome Content, looks very helpful for me and especially way of explanation is too simple