The Law of Coulomb

Coulomb’s law also known as Coulomb’s inverse-square law, is a hypothetical law of physics that provides a relationship between the strength of the electrostatic force between two charged particles. The electrostatic force between charged particles at rest is typically called Coulomb force.

In 1785 the law was defined by French physicist Charles-Augustin de Coulomb, hence the title. Coulomb’s law was an important step forward in the field of physics as it provided a clear and distinct relationship between charged particles.

The convention states that the strength of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between the charged particles.

The force acts in a straight line connecting the two point charges. If the charges are alike, the electrostatic force between them is repellent. If they are unlike, the force between them is attractive.

Being inverse-square law, the law is comparable to Isaac Newton’s inverse-square law of ubiquitous gravitation, but gravitational forces are consistently attractive, while electrostatic forces can be repulsive. Coulomb’s law can be utilized to obtain Gauss’s law and vice versa.

Limitations of the Law

There are three conditions to need to be satisfied for the rationality of Coulomb’s inverse square law:

The charges must have a spherically uniform.It is only applicable in cases when the inverse law worksThe charges must be point charges at rest

Now, Coulomb’s law of magnetism is nothing but a modified form of the above law. It states that the force of the magnetic attraction or repulsion between two magnetic poles is directly proportional to the product of the magnitude of the poles and inversely proportional to the square of the distance between the two poles.

This law allows for the strength of attraction or repulsion between two magnetic poles to be explicitly expressed. Therefore, we can clearly understand how important this law and in fact, it has several applications in experimental physics.

Now, let’s draw from the similarities between electric charges and magnetic poles and try to understand Coulomb’s law of magnetism a little better.

Although magnetic monopoles do not exist, for theoretical consideration let us take two magnetic monopoles m1 and m2. Now, similar to electric charges, the direction of the force between two pole acts in a straight line joining the poles. When the two poles are identical (North-North or South-South), they repel each other whereas the opposite poles (North-South) attract each other. As we bring the poles closes to each other, the force of attraction/repulsion between them becomes stronger. Hence, the force is inversely proportional to the distance between the two poles.

So, these were the basics of magnetism and Coulomb’s law. We can clearly see the similarities between the laws of magnetism and electrostatics and we can use this to our advantage while learning these concepts in the future.