Electrostatics is an old form of science. From the very past, humans have been fascinated by Electrostatics, discharge and lightning or wool or silk cloths that attract light objects after rubbing. You’d possibly have done a plastic ruler stick game with small light pieces of paper. This is often precisely the topic we are becoming to debate about it. Static means anything that does not move or change with time. Electrostatics deals with the study of forces, fields, and potentials arising from static charges. In this Physics article, you are going to learn Coulomb’s Law of Electrostatics.
Coulomb’s Law of Electrostatics
Coulomb’s law of Electrostatics could also be a quantitative statement about the force between two point charges. According to this law, if two stationary and point charges \(q_1\) and \(q_2\) are kept at a distance r, then it is found that the force of attraction or repulsion between them is –
\(F=k{q_1q_2\over{r^2}}\)
Where k = proportionality constant.
The value of k = \(8.988 \times 10^9 Nm^2/C^2\) ≈ \(9.0 \times 10^9 Nm^2/C^2\)
- If the charges are like, the force is of repulsion.
- If the charges are unlike, the force is of attraction.
Derivation of Coulomb’s Law of Electrostatics
According to Coulomb’s Law, we know that,
The electrostatic force is directly proportional to the product of the charges.
\(F{\propto}q_1q_2\)
The electrostatic force is inversely proportional to the perpendicular distance between the two charges.
\(F\propto\frac{1}{{{r^2}}}\)
Together we get,
\(F\propto({q_1}{q_2})/{r^2}\)
If we remove the proportionality sign we introduce a proportionality constant ‘k’, also known as Coulomb’s Constant. The value of this constant is dependent upon the permittivity of the medium.
The value of ‘k’ is given by
\(k=\frac{1}{4\pi\epsilon_o}\) where \({\epsilon_o}\) = permittivity of vacuum.
For any other medium between the two charges, we can find out the value of Coulumb’s constant to be,
\(k=\frac{1}{4\pi\epsilon_r\epsilon_o}=k=\frac{1}{4\pi\epsilon}\)
Where,
\(\epsilon_r \) is the permittivity of the medium and
\(\epsilon\) is the permittivity of the medium with respect to vacuum.
