Profile
Settings
Refer your friends
Sign out
In 1785, a French physicist named Charles Augustin de Coulomb coined a real mathematical relationship between two electrically charged objects. Coulomb’s law, often known as Coulomb’s inverse-square law, is an equation for the force that causes bodies to attract or repel each other.
Coulomb’s law
According to Coulomb’s law the force of attraction or repulsion between two charged bodies is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. It acts on the line that connects the two charges that are called point charges.
Electrical force
The electrical force, like all other forces, is usually measured in Newtons. The electrical interaction’s intensity is a vector quantity with both magnitude and direction because it is a force. The electrical force’s direction is determined by whether the charged objects are charged with like or opposing charges, as well as their spatial orientation. With a little thinking and knowledge of the two objects’ charge types, the direction of the force on either of them can be determined.
Coulomb’s law equation
The equation of coulomb’s law can be written as:
F=KQ1Q2/d2
where Q1 is the quantity of charge on object 1 (in Coulombs), Q2 denotes the quantity of charge on object 2, and d denotes the separation distance between the two items (in metres). The sign K stands for the Coulomb’s law constant, which is a proportionality constant. This constant’s value is determined by the medium in which the charged objects are immersed. The value of K in the case of air is 9×109N m2/C2. The value of k can be lowered by up to 80 times if the charged objects are present in water. When the units of charge (Coulombs) and distance (metres) are replaced into the equation, the units of charge (Coulombs) and distance (metres) are cancelled, leaving a Newton as the unit of force.
When two items function as point charges, the Coulomb’s law equation provides a precise representation of the force between them. When a charged conducting sphere interacts with other charged objects, it behaves as though all of its charge is concentrated in its centre. While the charge is evenly distributed around the sphere’s surface, the charge’s centre can be regarded as the sphere’s centre. The sphere functions like a point charge, with the extra charge at the centre. The distance d in the equation is the distance between the centres of charge for both objects because Coulomb’s law applies to point charges (not the distance between their nearest surfaces).
Relative permeability
The relative permeability for any medium is given as:
∈r=(force between two charges in air) / (force between same charges in different medium)
Here r is the relative permeability.
Limitations of coulombs law
Only the point charges at rest are covered by the law.
Coulomb’s Law can only be used in situations where the inverse square law is followed.
When charges have an arbitrary shape, it is difficult to apply Coulomb’s law because the distance between them cannot be determined.
The charge on the huge planets cannot be calculated directly using the law.
Necessary points on coulomb’s law
For different separations, if the force between two charges in two different media is the same, then:
When two identical conductors with charges q1 and q2 are separated by a distance d, the force of attraction or repulsion between them is F0. Also, if they come into contact and then are removed by the same distance, a new force is created between them that is
When two electrons are separated by a given amount of space, then the ratio of electrical force to the gravitational force is 1042.
When two protons are separated by a given amount of space, then the ratio of electrical force to the gravitational force is 1036.
When one proton and one electron is separated by a given amount of space, then the ratio of electrical force to the gravitational force is 1039.
Applications of Coulomb’s law:
Calculate the distance between the two charges as well as the force between them.
The Coulomb’s law can be used to compute the electric field.
Calculate the force acting on a single point as a result of the existence of many points (Superposition Theorem).
Conclusion
Coulomb’s law says that in a vacuum, the force F between two-point charges, Q1 and Q2, is proportional to their product and inversely proportional to their distance apart, r. Each charge is said to generate an electric field, the strength of which is measured at any given position by the force exerted per unit charge. As a result, the electric field strength E1 due to Q1 at the position of Q2 equals F/Q2 in newton per coulomb. Furthermore, the work per unit charge, in joules per coulomb, required to transport a positive charge from one point to the other is defined as the potential difference, in volts, between two points in an electric field.
