Introduction to Electricity & Electromagnetism

Introduction to Electricity

• Electricity involves physical phenomena related to the presence and flow of electric charges.

• It manifests in various phenomena like lightning, static electricity, electromagnetic induction, and electric current flow.

• Electrification involves the loss or gain of electrons.

• For electrification to occur, electrons must be mobile.

• Some materials, like metals, allow the movement of electrical charges, and are called electrical conductors.

• Other materials, like glass, plastic, and silk, impede the movement of electrical charges and are called electrical insulators.

Theory of Electromagnetism

• Magnetism and electricity are closely related; magnetism, natural or artificial (electromagnetism), allows obtaining electricity easily and inexpensively.

• James Clerk Maxwell, a Scottish mathematician, first explained the relationship between electricity and magnetism around 1870.

• Electromagnetism is magnetism produced by electricity effects.

• Electromagnetism has numerous industrial applications, for example: electric generators such as dynamos or alternators, transformers, relays, and motors.

Fundamentals of Electromagnetism

• When a coiled cable wound around a support is traversed by an electric current, it creates a magnetic field around it, like a natural magnet.
• The magnetic field created by the coil increases with the number of coil turns and the intensity of the circulating current.

Applications of Electromagnetism

• Alternators, dynamos, or magnetic flywheels work on the principle of current induced in a winding when subjected to a magnetic field variation.

Transformers

• Transformers are based on the phenomenon of self-induction and mutual induction.

• Transformers consist of primary and secondary windings coiled around a ferromagnetic core material.

• The voltage induced in the secondary depends on the turns ratio between the primary and secondary, and the current intensity through the primary at interruption.

• Self-induction limits a coil's charging time, especially when saturation time is limited, like in ignition transformers operating at high speeds.

Electron in Matter

• Electricity originates from the movement of a tiny particle that forms atoms, called an electron.

• An atom, the smallest portion of matter, has a nucleus with protons (positive charge) and neutrons (no charge).

• An atom can have many electrons orbiting the nucleus.

• Phenomena can remove electrons from outer orbits, causing a deficit of negative charges and creating a positive ion.

• Electron displacement from its orbit creates a "hole" that attracts an electron from a nearby atom, triggering a cascade of electrons and creating electron circulation.

• The force that makes electrons circulate in a conductor depends on the electron difference between the conductor's ends.

• If one end has many electrons and the other has few, electrons naturally circulate towards the electron deficient end to reach equilibrium.

• Electrons have a small mass and a unit of negative electrical charge.

• Protons have a much larger mass than electrons and a unit of positive electrical charge.

• Neutrons have no electrical charge and have the same mass as protons.

• An atom consists of a nucleus and a cortex.

• The nucleus contains clustered protons and neutrons.

• The hydrogen atom´s nucleus has only one proton.

• The sodium, for example, has eleven protons e twelve neutrons.

• The cortex is formed by layers, in which electrons move in circular orbits around the nucleus.

Electric Machines

• Electrical machines are mechanisms that generate, harness, or transform electrical energy..

• Generators convert mechanical energy into electrical energy.

• Motors convert electrical energy into mechanical energy

• When a current-carrying conductor is within a magnetic field, it moves perpendicularly to the magnetic field.

• If the magnetic field is horizontal, the conductor moves up or down, depending on the current's direction.

• Replacing the conductor with a current-carrying loop makes one side rise and the other fall, causing the loop to spin due to current entry and exit on opposite sides.

Electric Motors

• Electric motors are rotating electrical machines that transform electrical energy into mechanical energy.

• Electric motors have advantages like economy, cleanliness, convenience, and operational safety.

• Electric motors replaced many energy sources in industries, transportation, commerce, and homes.

• Attraction-repulsion forces between a magnet and a current-carrying coil drive electric motors.

• Building an electric motor requires a coil (windings with a beginning and end), a magnet, and a battery to send current through the windings.

• Modern electric motors have multiple windings (coils) in the rotor (rotating part) and a large magnet (stator) around the rotor on the motor's fixed part.

• Motors exist with coils on the stator and a magnet as the rotor.

Dynamos and Alternators

• Michael Faraday discovered that moving an electrical conductor within a magnetic field (magnet) generates voltage.
• A closed circuit with a receptor causes an electrical current.

Dynamo

• To extract the generated current from the loop, collectors that rotate with each loop are are placed with fixed brushes on the conductor
• It is noticeable that the collectors are cut.

Alternator

• The same brush would change polarity (from plus to minus) within each of the loops:
• Is equal but without cut collectors.

Electricity Production

• With knowledge of electricity generation principles from magnetic fields and electron movement, commercial electricity production can use power plants fueled by biogas, geothermal, wind, thermal, and hydroelectric sources.

Electric Current

• The two types of electric current are: the alternating current and the direct current.

Direct current

• Direct Current (DC) is current where charges move in one direction.
• Batteries produce this type of electricity.

Alternating current

• Alternating current (AC) is current whereby charges move in one direction and then the opposite.

• Its Polarity changes cyclically within the circuit.

• The number of times (cycling) or "frequency" that the current changes per second is measured in hertz (Hz).

Potential Difference

• The Potential difference (or tension) between two points is the energy that is required to deliver a positive charge in order to displace it from one to another.

• The measurement unit is the volt (V).

• In the same way we need presure for the water to circle within a pipe, tension is required for electrical current to circulate within a pipe.

• The instrument used to measure the difference in potential, tension or voltage, is the voltmeter.

• It connects to the circuit to measure the electrical power.

Current Intensity

• Is the quantity of electrical charge that circulates from a conductor at a unity of time.

• Its unity is the ampere (A). Corresponds to one coulomb of charge per second.

• The instrument that measures intensity is the amperimeter

• It is serially connected to the circuit to measure.

Electricity production based on fossil combustibles

• The generation of electricity from fossil combustibles is known as the thermal power plant, although other elements as combustibles exist for instance, coal, gas, gasoil, nuclear energy, wood.

• The process follows the same principle.

• The generator connects itself to a transformer that elevated voltage, sending them through high tension transmission lines at nominal values from 25 to 132 kilovolt.

• That voltage is variable depending from the company designs.

• Increasing transport voltages is necessary in view that high tension cables must travel larger distances, its copper cables give resistance to the current transported, causing the decreasing of main output to the distribution center.

• Generally, the same principle follows an electrical energy production system that utilizes other combustible types, one considers that this is very polluting and pricy since it sends large amounts of CO2 to environmental media.

• Energy demand in the world has remained sustained at 14 percent.

• This is due to the growing world population, and the industrial development and improvement of living conditions of developing countries who are growing demand for energy.

• The core primary sources of energy are Combustibles, nuclear fission, and renewables.