Electric Technology

Electric Field Charge Density | Electric Charges| Intensity| Coulomb’S Law

About Electric Field Charge Density

Relation of electric Field to Charge Density Since the charge is that the supply of electrical field, The study of static charges is called electrostatics. Firstly, we get introduced to charges and frictional electricity. Then comes the most vital laws of electrostatics which are the coulombs law. But to appreciate the power of coulombs law and superposition principle we have to enlarge our discussion through the concept of the electric fields which is a geometrical way of perceiving the properties of electric charge. An electrostatic arrangement called the electric dipole is discussed because subsequently, we shall deal with atoms and their influences. To deal with symmetrical charge configurations quickly, an additional discussion on gauss’ law through its various applications are also useful.



There are 2 types of electric charges. American scientist Benjamin franklin named them positive and negative charges. When a glass of rod was rubbed on silk, then due to friction, some electrons get transferred from the rod to the silk and hence by convention the glass rod acquires positive charges and the silk acquires negative charges. When a plastic rod is rubbed on wool, then some electrons get transferred from the wool to the plastic rod sand hence the plastic rods becomes negatively charged and the wool becomes positively charged. Generally, the like charges repel and the unlike charges attract each other. The property which differentiates the 2 kinds of charges is called the polarity of charges. If an object possesses an electric charge, it is said to be electrified or charged. When the net charge is 0 it is said to be neutral.


Some substances easily allow passage of electricity through them while others do not. Substances that allow electricity to flow through them easily are called conductors. They have electrons that are free to move inside the material. Metals, human and animal bodies, earth are all examples of conductors. Non-metals for example glass, plastic wood are called insulators since they do not pass electricity through them. There is also a 3rd category called the semiconductors which are the intermediates between the conductor and the insulators and they allow the partial movement of charges through them.


Common symbolsQ
SI unitcoulomb
Other unitselementary chargefaradayampere-hour
In SI base unitsC = A s
DimensionT I

Now as we already know that 2 oppositely charged bodies attract each other but it has also been our observation that a charged body attracts a neutral body as well. This is explained on the basis of charging by induction. In the induction process, 2 bodies at least where one of them is charged are brought very close but they never touch each other.

You can read more from here : https://en.wikipedia.org/wiki/Electric_charge






The 1st one says that a system contains 2-point charges suppose q1 and q2 then the total charge of the system is obtained by simply adding the charges algebraically q1 and q2. The charges add up like the real numbers or they are scalers like the mass of a body. The charge has magnitude but no direction similar to the mass. However, there is 1 difference between the charge and the mass. Mass is always positive whereas the charge can be either positive or negative.

The 2ndone says that the total charge of the isolated system is always conserved. It is not possible to create or destroy net charge carried by an isolated system.

The 2nd one signifies that all free charges are an integral multiple of a basic unit of charge denoted by e. thus the charge q on a body us always expressed as q=ne where n is the positive or negative integer.

The basic unit of charge is the charge that an electron or a proton carries. By convention, the charge on an electron is taken to be negative and is written as -e. the fact that the electric charge is always the integral multiple of e is termed as quantization of charge. The quantization of charge was 1st described through the experimental laws of electrolysis by Michael Faraday.


Coulomb’s law is a quantitive statement about the force between 2-point charges. Coulomb measured the force between 2-point charge and found that it varied inversely as the square of the distance between the charges and was directly proportional to the product of the magnitude of the 2 charges and acted along the line joining the 2 charges.


It is the strength of an electrical field at a given purpose or it can also be outlined because of the force fully-fledged by a unit electric charge placed in the field of force.

Symbol E

Formula Force/ Charge or F/Q

Unit Newton/ Coulomb

Nature of Quantity Vector

Dimensions [ML/T2] / [AT]

[ ML/ T3A]


Thus the electric field is a vector way of representing the space around the charge which helps in calculating the force on one another. Like the electric field at a point in space due to a single charge, the electric field at a point p in space denoted by the position vector, due to the system of charges can be calculated by using coulomb’s law and the superposition principle together. The physical significance of the concept of this electric charge filed emerges only when we go beyond electrostatics and deal with the time-dependent phenomena to be dealt with.

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Dewakar Pandey
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