Electricity or electrical energy represents a set of physical phenomena separated from magnetism that involves the presence and the motion of electrically charged particles.
Electrical energy is produced today from different sources of power such as coal, oil, natural gas and nuclear as fossil fuels and solar, wind, hydro, geothermal, biomass, tidal, wave, etc. as renewables.
What is Electrical Energy?
Electricity or electrical energy represents a form of energy generated by the flow of electric charge.
Electrical energy produces attraction between particles with opposite charge and repulsion between particles with the same charge.
The movement (flow) of the charged particles through an electric cable or a conductive medium is called electric current or electricity.
Other common phenomena related to electricity include lightning, electric heating, electric discharges and static electricity.
If the presence of an electric charge (positive or negative), an electric field is produced.
The movement (flow) of an electric charge represents electric current or electricity and generates a magnetic field.
Electrical energy represents the potential energy that is stored due to the presence of charged particles or electric fields.
A form of electrical potential energy is the static electricity that is produced through an imbalance or separation between the positive and negative charges on an object.
When enough electrical charge is accumulated, the electrical energy can be discharged under the form a spark or even lightning.
The spark or lightning produced this way generates electrical kinetic energy.
Brief History of Electricity
Ancient people were aware of lightning produced during storms and electric fish, and they’ve considered these fishes as the guardians of other fishes.
Around the 15th century, the Arabs were pretty close to the discovery of the identity of lightning, and electricity produced from any other source because they applied the word lightning in their language to electric ray.
Before the year 1600, electricity was mostly known due to natural phenomena such as lightning and electric fishes, but in the year 1600, William Gilbert (an English scientist) started to carefully study both electricity and magnetism.
In the 18th century, Benjamin Franklin (one of the founding fathers of the U.S.) made an extensive research on electricity, and he even sold most of his possessions to fund his scientific work.
Ben Franklin’s Kite Experiment
Franklin is also known for the famous phenomenon in which he attached a metal key to the bottom of a dampened kite string and he decided to fly the kite during a storm to see if lightning has electrical nature.
Several sparks have started to jump from the key to the back of his hand, which have proved that lightning is indeed an electrical phenomena.
Luigi Galvani (an Italian physician, physicist, biologist and philosopher) published in 1791 a study about bioelectromagnetics (his discovery), in which he showed that electricity is a medium used by neurons to pass signals to the muscles.
Alessandro Volta (an Italian physicist, chemist and pioneer of electricity) created his first battery (a voltaic pile made of alternating layers of zinc and copper) in 1800, and provided scientists with an advanced source of electricity instead of the electrostatic machines used before.
Hans Christian Ørsted (a Danish physicist and chemist) and André-Marie Ampère (a French physicist and mathematician) discovered electromagnetism in 1819 and 1820, and showed the unity between the electric and the magnetic phenomena.
Michael Faraday and the first electric motor
Michael Faraday (an English scientist) is the creator of the first electric motor in 1821.
The first electric circuit was mathematically analysed by Georg Ohm (a German physicist and mathematician) in 1827.
Electricity and magnetism (and also light) were finally linked in the four-part paper entitled “On Physical Lines of Force” and published by James Clerk Maxwell (a Scottish scientists in the field of mathematical physics) in 1861 and 1862.
In the late 19th century, electrical engineering has made an impressive progress due to the work of many people such as: Alexander Graham Bell, Thomas Edison, Ottó Bláthy, Galileo Ferraris, Ányos Jedlik, Oliver Heaviside, William Thomson, Charles Algernon Parsons, 1st Baron Kelvin, Werner von Siemens, Reginald Fessenden, Joseph Swan, Nikola Tesla and George Westinghouse, which turned the electricity from only a curiosity into a driving force of the Second Industrial Revolution.
Heinrich Rudolf Hertz (a German physicist) discovered in 1887 that electrodes illuminated with ultraviolet light are creating electric sparks way more easily.
The photoelectric effect
Albert Einstein (a German theoretical physicist that created the theory of relativity) published in 1905 a paper in which he explained the experimental data obtained in the study of the photoelectric effect.
He explained that the photoelectric effect is a result of light energy being carried in small packets to energize electrons.
Einstein received the Nobel Prize in Physics in 1921 for the discovery of the law of the photoelectric effect.
The photoelectric effect is used today by solar cells to produce electricity.
The first solid-state device (an electronic equipment that uses semiconductor devices such as diodes, transistors and integrated circuits) was the “cat’s-whisker detector”, which is a device providing a physical contact between a mineral crystal (germanium crystal) or between two mineral crystals with the purpose of rectifying radio frequency alternating current to allow the radio program to be heard in the headphones.
The flow of the electric current was understood in two different forms such as: a flow of negatively charged electrons, and as a flow of positively charged electron deficiencies that were called holes.
These charges and holes have been defined in terms of quantum physics.
The first transistor
The first transistor (a semiconductor device used to amplify or switch between electronic signals and electricity) has been created in 1947.
Other common solid-state devices such as microprocessor chips, RAM memory (used today by the USB flash drives), and hard disk drives (HDD units) have been later created.
In the 50’s and the 60’s took place the transition from vacuum tubes to semiconductor diodes, transistors, integrated circuits (ICs) and also the light-emitting diode (LED).
What is Electricity?
Electricity represents a set of phenomena related to charge.
Charge is a property of the particles located in and around the atoms.
An atom has protons and neutrons in its nucleus and electrons surrounding the nucleus.
The protons in the nucleus have a positive charge, while the electrons have a negative charge.
If the number of protons and electrons is the same in the atom, we say that the atom is balanced.
By removing an electron from a balanced atom, the atom becomes positively charged (more protons than electrons in the atom), while by adding an electron to the balanced atom, the charge of the atom will become negative (more electrons than protons in the atom).
A charged atom (electrically charged) is an unbalanced atom, and is called an ion.
Two electrons with the same charge will repel each other, while a positively charged atom will attract a negatively charged electron.
What is DC Electricity?
DC electricity stands for direct current and refers to the fact that the charges (charged electrons) are moving in one direction (like a river).
The charge can move through a wire, the electrons are actually moving pretty chaotic, but their overall movement is in one direction.
The batteries used today by our gadgets are producing DC electricity.
When we connect wires to the terminals of the battery the chemistry inside the battery starts moving charged atoms (ions) between the battery terminals and at the same time electrons will move in the wires connected to those terminals, and the result will be DC electricity (electrons are flowing in one direction through the wire).
Electrons are not moving very fast, however, the effects of the electromagnetic forces involved here are propagated very fast (close to the speed of light).
What is AC Electricity?
AC electricity stands for alternating current, which means that the electrons move in one direction, then in reverse direction, and then reverse again.
Electrons will alternate in directions in the case of AC electricity and anything we plug into a wall socket in the house uses AC electricity.
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However, when we plug an adapter (most adapters are converting electricity from AC to DC) it means that the connected device uses DC electricity (like the electricity produced by batteries).
AC electricity is generated today by nuclear power plants, hydroelectric power plants and coal-fired plants.
Nuclear power plants and coal-fired power plants are producing steam that is used to spin the rotor of a generator.
Hydroelectric power plants use an underwater turbine that spins under the kinetic force of the moving water.
The underwater turbine also spins the rotor of a generator.
How Does a Generator Produce Electricity?
This type of generator has a rotor consisting in a ring of magnets that rotates, and a stator that has coils of wire on it and is stationary.
When the rotor spins under the action of the steam or water, the magnets of the rotor will pass the wires of the coils and this will cause the electrons to move in the wires.
The magnets on the rotor and the coils on the stator are arranged in such a way so the interaction between them to make the electrons move back and forth and produce AC electricity.
Solar panels produce DC electricity and we are using inverters to turn DC electricity into AC electricity.
However, the DC electricity produced by solar panels can be directly stored in batteries and then turned into AC electricity by the inverter for house use.
Electric Units
Today, we are using several electric units to measure electricity.
To better understand the meaning of the electric units used to measure electricity, we need to first define demand and capacity.
Demand
Demand defines the instantaneous amount of work required to perform a specific function such as powering a device or creating light using a bulb.
Capacity
Capacity defines the instantaneous ability to provide the energy required to do work.
Demand and capacity are measured in units such as watts, kilowatts, megawatts, gigawatts and terawatts.
1 Kilowatt (KW) equals 1,000 watts (W);
1 Megawatt (MW) equals 1 million watts (W);
1 Gigawatt (GW) equals 1 billion watts (W);
1 Terawatt (TW) equals 1 trillion watts (W).
When we turn on a 20 watt LED light bulb in a room, we are creating a demand of 20 W.
In order for the LED bulb to light, 20 W of capacity must be available at the generator and along the entire path between the bulb and the energy source.
Units of Energy or Usage
Energy or usage
Enargy or usage defines the demand or capacity multiplied by the amount of time that the demand or capacity is in use.
Energy or usage is measured in units of Watt-hours, Kilowatt-hours, Megawatt-hours, Gigawatt-hours and Terawatt-hours.
Let’s go back to our 20 W LED light bulb, and we see that the light bulb uses 20 watts of energy each hour, which means that the LED light bulb will consume 20 Watt-hours (Wh) for one hour of usage.
By leaving the LED light bulb on for 24 hours, it will consume 20 W X 24 hours, which equals 480 Watt-hours (Wh), or 0.48 Kilowatt-hours (KWh) of energy.
Other Units Used to Measure Electricity
Volt
Volt with the symbol V received its name after Alessandro Volta (an Italian physicist, chemist and pioneer of electricity and power) and can be defined as a difference in electrical potential energy, per unit of charge, between two points of a wire.
Voltage also refers to the electrical pressure that forces the electrons to move in a specific direction in the conductor.
Ampere
Ampere (amp) with the symbol A received its name after André-Marie Ampère (a French physicist and mathematician) and refers to the amount of electrons that are flowing per second through a conductor.
1 Ampere = 6.24 x 1018 electrons flowing through a certain point per second.
Ohm
Ohm with the symbol Ω received its name after Georg Simon Ohm (a German physicist and mathematician) and measures the electrical resistance, which is the difficulty to pass an electric current through a conductor.
Farad
Farad with the symbol F received its name after Michael Faraday (an English scientist that contributed to the study of electromagnetism and electrochemistry) and measures the electrical capacitance or the capacity of a body to store an electrical charge.
Henry
Henry with the symbol H received its name after Joseph Henry (an American scientist which was the first Secretary of the Smithsonian Institution) and measures electrical inductance, which is an effect caused by the magnetic field created by the current flowing through a conductor and acting back on the conductor.
Coulomb
Coulomb with the symbol C received its name after Charles-Augustin de Coulomb (a French military engineer and physicist) and measures the electric charge transported by an electric current of 1 Ampere during 1 second.
Joule
Joule with the symbol J received its name after James Prescott Joule (an English physicist, mathematician and brewer) and refers to the use of 1 Watt of energy for 1 second.
1 Watt for 1 second equals 1 Joule, 1 Watt for 60 seconds equals 60 Joules, and 1 Watt of energy for 1 hour equals 3,600 Joules or 3.6 Kilojoules.
Hertz
Hertz with the symbol Hz received its name after Heinrich Rudolf Hertz (a German physicist) and refers to the electrical frequency.
In an AC (alternative current) system frequency is the rate at which the electron flow changes direction.
Frequency is measured in Hertz, and 1 Hertz is defined as one cycle per second.
