Coulomb’s Law and its Significance
– Coulomb’s Law is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.
– It was first published in 1785 by French physicist Charles-Augustin de Coulomb.
– Coulomb’s Law was essential to the development of the theory of electromagnetism.
– It allowed meaningful discussions of the amount of electric charge in a particle.
– The law states that the magnitude of the electrostatic force between two point charges is directly proportional to the product of their charges and inversely proportional to the squared distance between them.
Like Charges Repel, Opposite Charges Attract
– Coulomb discovered that bodies with like electrical charges repel each other.
– The repulsive force between two balls electrified with the same kind of electricity follows the inverse proportion of the square of the distance.
– Coulomb also showed that oppositely charged bodies attract each other according to an inverse-square law.
– The force between charges is along the straight line joining them.
– If the charges have the same sign, they repel; if they have different signs, they attract.
Comparison with Newton’s Law of Universal Gravitation
– Coulomb’s Law is similar to Newton’s Law of Universal Gravitation, but with some differences.
– Gravitational forces always make things attract, while electrostatic forces can make charges attract or repel.
– Electrostatic forces are much stronger than gravitational forces.
– Coulomb’s Law can be used to derive Gauss’s Law, and vice versa.
– In the case of a single point charge at rest, both laws are equivalent, expressing the same physical law in different ways.
History of Coulomb’s Law
– Ancient cultures knew about static electricity, such as rubbing amber with cat’s fur to attract light objects.
– In 1600, William Gilbert distinguished between the lodestone effect and static electricity produced by rubbing amber.
– The word ‘electric’ and ‘electricity’ originated from the Greek word for amber.
– Early investigators in the 18th century, such as Daniel Bernoulli and Alessandro Volta, measured the force between charged plates.
– Joseph Priestley proposed that electrical force followed an inverse-square law, similar to Newton’s law of gravitation.
Scalar and Vector Forms of Coulomb’s Law
– Coulomb’s Law can be stated as a simple mathematical expression in scalar form.
– The scalar form gives the magnitude of the electrostatic force between two point charges.
– The vector form of Coulomb’s Law includes the direction of the force.
– The magnitude of the forces experienced by two charges will always be equal.
– The law of superposition allows Coulomb’s Law to be extended to include any number of point charges. Source: https://en.wikipedia.org/wiki/Coulomb%27s_law
Coulomb's inverse-square law, or simply Coulomb's law, is an experimental law of physics that calculates the amount of force between two electrically charged particles at rest. This electric force is conventionally called electrostatic force or Coulomb force. Although the law was known earlier, it was first published in 1785 by French physicist Charles-Augustin de Coulomb. Coulomb's law was essential to the development of the theory of electromagnetism and maybe even its starting point, as it allowed meaningful discussions of the amount of electric charge in a particle.
The law states that the magnitude, or absolute value, of the attractive or repulsive electrostatic force between two point charges is directly proportional to the product of the magnitudes of their charges and inversely proportional to the squared distance between them. Coulomb discovered that bodies with like electrical charges repel:
It follows therefore from these three tests, that the repulsive force that the two balls – [that were] electrified with the same kind of electricity – exert on each other, follows the inverse proportion of the square of the distance.
Coulomb also showed that oppositely charged bodies attract according to an inverse-square law:
Here, ke is a constant, q1 and q2 are the quantities of each charge, and the scalar r is the distance between the charges.
The force is along the straight line joining the two charges. If the charges have the same sign, the electrostatic force between them makes them repel; if they have different signs, the force between them makes them attract.
Being an inverse-square law, the law is similar to Isaac Newton's inverse-square law of universal gravitation, but gravitational forces always make things attract, while electrostatic forces make charges attract or repel. Also, gravitational forces are much weaker than electrostatic forces. Coulomb's law can be used to derive Gauss's law, and vice versa. In the case of a single point charge at rest, the two laws are equivalent, expressing the same physical law in different ways. The law has been tested extensively, and observations have upheld the law on the scale from 10−16 m to 108 m.
