Coulomb's Laws of Electrostatics

COULOMB'S LAWS OF ELECTROSTATICS

I guys Today I am going to explain about Coulomb's laws . Before going to laws you have know about Electrostatics

1) Electrostatics

Now, we will discuss the behaviour of static electricity and the laws governing it. Infact, electrostatics is that branch of science which deals with the phenomena associated with electricity at rest.

It has been already discussed that generally an atom is electrically neutral i.e. in a normal atom

the aggregate of positive charge of protons is exactly equal to the aggregate of negative charge of the electrons.

If, somehow, some electrons are removed from the atoms of a body, then it is left with a preponderance of positive charge. It is then said to be positively-charged. If, on the other hand, some electrons are added to it, negative charge out-balances the positive charge and the body is said to be negatively charged.

In brief, we can say that positive electrification of a body results from a deficiency of the electrons whereas negative electrification results from an excess of electrons.

The total deficiency or excess of electrons in a body is known as its charge.

2) Absolute and Relative Permittivity of a Medium

While discussing electrostatic phenomenon, a certain property of the medium called its permittivity plays an important role. Every medium is supposed to possess two permittivities :

(i) absolute permittivity (ε) and

(ii) relative permittivity (εr).

For measuring relative permittivity, vacuum or free space is chosen as the reference medium. It has an absolute permittivity of 8.854 × 10−12 F/m

Absolute permittivity ε0 = 8.854 × 10−12 F/m

Relative permittivity, εr = 1

Being a ratio of two similar quantities, εr

has no units.

Now, take any other medium. If its relative permittivity, as compared to vacuum is εr

, then its absolute permittivity is ε = ε0 εr F/m

If, for example, relative permittivity of mica is 5, then, its absolute permittivity is

ε = ε0 εr = 8.854 × 10−12 × 5 = 44.27 × 10−12 F/m

Coulomb's laws: -

First law

Like charges of electricity repel each other, whereas unlike charges attract each other.

Second law