Fundamentals of Electric Current and Circuits

The Electron and Electric Current

The electron is the fundamental element of the electric current, as it has electric charge and can move from one atom to another.

Electrostatic Force (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 that separates them.

A coulomb is the charge that a body possesses when, facing another body of the same charge at 1 meter distance in a vacuum, it repels with a force of $9.10^9$ N.

Electric Circuit Components

An electric circuit consists of a set of interconnected elements, so as to permit the permanent circulation of electric power.

• Generator: Is the device responsible for transforming any form of energy into electric energy.
• Drivers (Conductors): Are made of wires that connect the various circuit elements.
• Recipients (Loads): They are the basic elements of the electric circuit.
• Control and Maneuvering Elements: Determine the operating mode of the circuit.
• Protection Elements.

Electric Current Intensity

The intensity: the amount of charge that traverses a section of a conductor in unit time.

One ampere is the current that flows through a conductor when it carries a charge of one coulomb per second.

Potential Difference

The difference in potential between two points is the work required to transport the unit electric charge from one point to another.

Between two points there is a potential difference of one volt if, for transporting a charge of one coulomb, the work performed is one joule.

Electrical Resistance and Impedance

The electrical resistance is the quantity indicating the degree of difficulty of a material to the flow of electric current.

• Impedance: Is a quantity that establishes the correspondence between the voltage and current in a circuit powered by alternating current.

Energy and Power

The Joule effect is the phenomenon by which electric energy is converted into heat when electric current passes through a conductor.

Current density is called the relationship between the intensity of current through a conductor and its geometrical section.

Electric power is called the energy consumed by a receiver per unit of time.

One watt is the power of a receiver which consumes an energy of one joule each second.

Resistors and Capacitors

Resistor

A resistor is an element which opposes the passage of electric current.

Capacitor

A capacitor is an element capable of storing electric charge when subjected to a potential difference between its plates.