Fundamental Principles of Coulomb's Law and Electric Force

Coulomb's Law and Electric Force

Coulomb's Law: The electric force with which two resting charges, q₁ and q₂, attract or repel each other is directly proportional to the product of the charges and inversely proportional to the square of the distance d (or r) that separates them.

The force is a vector unit according to the direction of the charges. The constant k has a numerical value of 8.9874 × 10⁹. The unit of electric charge is the Coulomb (C): The Coulomb is the positive charge q which, when placed in a vacuum at a distance of 1 meter from another identical charge, repels it with a force of 8.9874 × 10⁹ N. This constant allows us to solve Coulomb's Law.

Permittivity and Mathematical Expression

The units are determined by the permittivity of the vacuum, which is given by the following expression:

Therefore, Coulomb's Law can be expressed in the following way:

• If the charges q₁ and q₂ have the same sign, the electric force is positive (+).
• If the charges q₁ and q₂ have opposite signs, the electrical force is negative (-).

Understanding Electric Current

Electric Current: Electrical current is the ordered movement of charges caused by the action of an electric field. There are two types of electric current: continuous and alternating.

• Continuous electrical current is produced when applying an electric field directed always in the same direction. Continuous electrical current implies the existence of a flow of electrons within the conductor always in the same sense.
• Alternating electric current is produced when the applied electric field is reversed periodically, such that the direction of the electric current is also reversed periodically. Alternating current (AC) involves a small vibration amplitude of the electrons within the conductor.

Fundamental Properties of Electric Charges

1st Law of Conservation of Charge: In any process that occurs in an isolated system, the total charge remains constant.

2nd Law of Quantization of Charge: Electric charge may not appear in any arbitrary quantity, but only in multiples of a fundamental electrical unit. This fundamental unit of electric charge is the charge of one electron.

Electrification Phenomena by Induction

Induction is the electrification of a conductor by the action of a body that is already electrically charged.

By bringing a positively charged body near a conductor, the electrons in the conductor are attracted to that body. This creates two zones in the conductor: the first with a negative charge located in the proximity of the positively charged body, and another with a positive charge located on the opposite side.

By bringing a negatively charged body near a conductor, the electrons are repelled by the body. This creates two zones in the conductor: the first with a positive charge in the proximity of the body, and another with a negative charge located on the opposite side.

Following induction, the conductor and the charged body attract each other. Insulation will electrify slightly by induction, which is why light substances (like cork) are attracted by electrified bodies.