Fundamentals of Electricity and Electrical Installations
Atoms and Electric Charge
An “atom” is the smallest part of a chemical element that retains its properties. “Electric charge” is the excess or defect of electrons in a body.
Electricity and Current
“Electricity” is the orderly movement of electrons through a material. “Sense of electricity” is the direction of moving electrons.
Classes of Electric Current
- Direct current (DC): The flow is constant and does not change direction.
- Alternating current (AC): The electron flow is variable and changes direction.
- Pulsating current: The flow of electrons is variable but does not change direction.
Electrical Properties of Materials
- Drivers offer little resistance to electron displacement.
- Insulators or dielectrics greatly resist electron displacement due to their atomic structure.
- Semiconductors are materials where the number of free electrons depends on temperature and impurities.
Electrical Circuits
An “electrical circuit” is a set of active (energy-providing) and passive (energy-dissipating) elements connected to allow electric current flow.
Types of Circuits
- Series circuit: Elements are connected end-to-end.
- Parallel circuit: Elements are connected to the same two points.
Resistance
“Resistance” or resistors introduce difficulty or resistance in a circuit.
Kirchhoff’s Laws
- First Law: The algebraic sum of currents arriving at a junction equals the sum of currents leaving.
- Second Law: In a closed circuit, the sum of voltages equals the sum of voltage drops.
Drivers, Resistivity, and Resistance
- Resistivity is the specific resistance of a material.
- Conductivity is the ease with which current passes through a material.
- Electrical resistance of a conductor is proportional to its length and resistivity, and inversely proportional to its cross-section.
Joule’s Law
Joule’s Law relates to heat generated by current flow in a conductor. The “quantity of heat” is proportional to the resistance, the square of the current, and time.
Protection Elements: Fuse
Overcurrent means the current exceeds the nominal value (In).
A “short circuit” is a low-resistance connection between two points, causing high current.
“Overload” is a non-fault condition causing a surge in current.
A “fuse” is a protective device that opens a circuit when current exceeds a predetermined value.
Electrical Installations
Low Voltage Electrical Installation
A set of devices and circuits for producing, converting, transmitting, distributing, or using electricity.
- Counters measure electrical energy consumption.
- A switch opens and closes a circuit, remaining in its state until activated.
- Buttons open and close a circuit only while being pressed.
- A tap is a control device with one input and two outputs.
- A crossover switch has two inputs and two outputs, allowing connection inversion.
- A teleruptor is a remotely operated switch.
- An automatic timer regulates the on-time of lighting installations.
Domotics
Domotics is the technology for automating and controlling home facilities to improve quality of life.