Static Electric Field | Electrostatic Induction | Electric Field Strength

There is a relation between seller and consumer, consumer buys product from the seller. Except of this connection of selling and buying there is another relation which is of donor and taker. Now from the same point of view we can divide electric charge. We know there are two types of charge present in the nature (i) positive and (ii) negative charge. In positive charge, there is mainly deficiency of electrons and in negative charge there are excess of electrons. Now, we can simply understand the concepts of charge from a very basic example. Take a dry comb, comb your hair (which should be dry) two to three times, now take that comb near tiny pieces of paper, you will see that the paper pieces are getting attracted to the comb. This is the very basic example of electric charge and static electric field. Due to friction there is movement of electrons between comb and hair, so one of them gets positively charged and another one gets negatively charged and as the paper is neutral (i.e. not charged) they get attracted to the comb. So, we can see that there is an attraction force works between charged particle and neutral particle, it has been seen further that there is repulsion between two same charged particles and attraction between two differently or opposite charged particles. This happens due to the field created around a particle. This can be understood if we imagine a glowing bulb, the bulb can be taken as the charge and the visible light is nothing but static electric field, the characteristic of field is similar to the light in the sense that the intensity of the field is greater near the source and it fades as we move further from the source. Now from another point of view we can say that static electric field is nothing but an intense space, in terms of power where work is done or needed to be done upon in presence of an electrically charged particle depending on the nature of the charged particle.

Electrostatic Induction

A positive charge lacks electrons, where as a negative charge has excess electrons. What about the phenomenon of attraction of a neutral particle by a charged particle, because we can understand the phenomenon of attraction and repulsion between oppositely charged particles and same charged particles, but how neutrally charged particles get attracted by charged particles. This can be explained by electrostatic induction. The word induction itself explains a lot, it means action which is not the result of direct contact. To explain the above explained phenomenon, we can say that when a neutral body is brought near the charged body, opposite charge is induced in the neutrally charged body near to the charged body and same charge on the opposite side. We can understand the phenomenon more accurately by a diagram.

Electrostatic Induction

Electrostatic Induction


From the diagram the very basic operation of electrostatic induction can be understood. Opposite charge is induced near the charge and similar charge is induced further from the charge. In a more easier way we can say that this phenomenon is actually the redistribution of electric charges inside a matter in a more organised manner and the orientation depends upon the inducing charge.

Electric Field Strength

We discussed earlier, what is electric field. Now in this article we will know about electric field strength. Mainly this term electric field strength is used when two charged particles are kept near to each other. During that time electric field due to both the charges create a resistant electric field and the strength of that field can be determined by Coulomb’s law. Now we need to know, what is Coulomb’s law?

This law states that the force between two charges

  1. is directly proportional to the product of the charges,
  2. inversely proportional to the square of the distance between them and
  3. depends on the nature of the medium surrounding the charges.

To show the relation mathematically among force ‘F’ between two point charges leaving charge ‘Q1’ and Q2 and placed at a distance ‘d’ from each other is given by

Where K is any constant, in SI system the force between two charges is given by

Here εo is the permittivity of vacuum = 8.854 x 10 − 12 F/m and εr is the relative permittivity of the surrounding medium. Depending on the force, the electric field strength is determined and expressed in v/m (volts per meter). This force is a vector quantity and has direction. And finally it can be said that any charged particle has an electric field around itself and the strength of this field depends on the charge of the particle.

Electric Field Intensity

Intensity means the magnitude or amount. Now field intensity similarly means the magnitude of the strength of the field. Basically electric field intensity is considered for point charges. If we give the definition of this term it would be like, the force experienced by an unit charge if placed at a distance ‘d’ from a charge ‘Q’. And This force exerted on the unit charge can be determined by the Coulomb’s law which is like

The electric field intensity is vector quantity(i.e. it has both magnitude and direction) and is devoted by ‘E’ and magnitude is given by

The intensity is felt more when the unit charge is placed at the nearest of the charge and it is lightest when at infinite distance.


Video on Electric Field

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