What concept does Coulomb relate to in electric theory?

Coulomb's work is fundamentally tied to the concept of electric charge. He is best known for formulating Coulomb's Law, which describes the force between two charged objects. This law states that the force 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 them. Essentially, it quantifies how electric charges interact with one another, demonstrating that like charges repel and opposite charges attract.

Understanding electric charge is vital because it lays the groundwork for the entire field of electrostatics and, more broadly, electromagnetism. The concept of charge is what enables the existence and behavior of electric forces, electric fields, and subsequently other related concepts like voltage and resistance.

The other concepts listed—voltage, resistance, and electric field—are important in their own right but rely on the existence and properties of electric charges to be well-defined. Voltage relates to the energy per unit charge, resistance affects current flow, and fields describe the influence charges have on one another across space. However, electric charge is the foundational concept that underpins Coulomb's contributions.