Electrical Circuit Fundamentals: Definitions and Concepts

Fundamentals of Electrical Circuits

An electrical circuit is a closed path in which electrons circulate. A basic circuit includes the following elements: a generator that provides power, a wire, a switch, and a receptor.

The continuous circulation of electrons through a circuit is called electric current.

Circuit Components

• Generators: Necessary to provide the energy required for electrons to move (e.g., batteries).
• Receptors: Devices that convert electrical energy into another type of energy (e.g., light bulbs, motors, resistors).
• Control Elements: Utilized for directing and interrupting the electric current (e.g., switches, pushbuttons).
• Protection Elements: If the current is too high in a circuit, cables and components can overheat and melt or stop functioning. To avoid this, fuses are used.

Material Classification

Materials are classified based on how easily electrons move through them:

• Conductors: Electrons move with ease within the interior of the material. Example: All metals.
• Insulators: Electrons cannot move freely. Examples: Wood, glass, plastic.
• Semiconductors: Have properties intermediate between insulating and conducting materials. Example: Silicon and germanium, used in the fabrication of microprocessors and computers.

Resistance and Conductance

Resistance is the opposition a material presents to the passage of electric current. Conductance is the inverse of resistance.

• Metals (Conductors): Resistance is almost null (very low).
• Insulators: Resistance is very high.

Key Electrical Quantities

Voltage or Potential Difference

The amount of energy that a battery or generator provides to move each unit of charge (electron) is expressed as voltage or potential difference, measured in volts (V).

Intensity of Electric Current

This is the quantity of electrons that cross the section of a conductor every second. It is calculated using the formula: I = Q / t (Charge divided by time).

Ohm's Law

The resistance a material opposes to the passage of electricity is the ratio between the voltage applied across its ends and the intensity of the current that traverses it.

Types of Current

Direct Current (DC)

If a device is connected to a battery, electrons always flow in the same direction and with a constant intensity.

Alternating Current (AC)

The electron movement changes direction, typically 50 times per second (50 Hz). The intensity is not always constant.

Effective Value of AC

The effective value of an alternating electrical signal is the value that a continuous signal would need to have to produce the same energetic effect.

Electric Power and Energy

Electric Energy is the energy that the generator provides to keep the electrons in motion. This energy is consumed by the receivers.

Electric Power: The ability of a receiver to transform electrical energy per unit of time.