What is Electricity?
We use electricity every day to power our electronic devices. And electricity is present throughout nature; from lightning emitted during storms to the synapses firing inside your body. But what is electricity?
Electricity is a naturally occurring phenomenon which takes many forms throughout nature.
This article will focus on “current” electricity – the electricity which flows through our electrical sockets and powers our electric appliances, to understand how electricity flows from a power source and through wires to provide power to our devices.
Electricity is briefly defined as the flow of electric charge. To begin to explain the fundamentals of electricity, we must start by focusing in on atoms, the basic building blocks of life and matter.
Atoms exist in 118 different forms as chemical elements such as hydrogen (H), nitrogen (N), oxygen (O), silicon (Si), phosphorus (P), carbon (C), and copper (Cu). Different types of Atoms can combine to make molecules, which build the matter we can physically interact with.
Atoms are tiny, stretching at maximum length of about 300 picometers (3×10-10 or 0.0000000003 meters). But even the atom isn’t small enough to explain how electricity works. For that, we need to look at the building blocks of atoms: protons, neutrons, and electrons.
Protons, neutrons and electrons: The Building Blocks of Atoms
An atom is made up of a combination of three distinct particles: electrons, protons, and neutrons. Each atom has a centre nucleus made up of densely packed protons and neutrons. Surrounding this nucleus of protons and neutrons are a group of orbiting electrons.
Every atom must have at least one proton. The number of protons in an atom is called the atom’s atomic number and defines what chemical element the atom represents. For example, an atom with just one proton is hydrogen; an atom with 29 protons is copper.
The proton(s) in an atoms’ nucleus is partnered with neutrons. These neutrons keep the protons in the nucleus and determine the isotope of an atom. However, as neutrons do not play a critical role in our understanding of electricity, this article will not focus on them.
Electrons are critical to the workings of electricity. In its most stable, balanced state, an atom will have an equal number of electrons as protons. As in the Bohr atom model (see diagram below), a nucleus with 29 protons (copper atom) is surrounded by an equal number of electrons.
The electrons that make up an atom are not all bound to the atom forever. The electrons on the outer orbit of the atom are called valence electrons. With sufficient outside force, a valence electron can escape the atom’s orbit and become free. Free electrons allow us to move charge.
Electricity is defined as the flow of electric charge. Charge is a quantifiable and measurable property of matter (like mass, volume or density) and can come in two types: positive (+) or negative (-).
In order to move charge we need charge carriers. Electrons always carry a negative charge, while protons are always positively charged. Neutrons as their name suggests, are neutral and have no charge. Both electrons and protons carry the same amount of charge, just a different type.
The charge of electrons and protons is important because it enables us to exert a force on them, which we call electrostatic force.
Electrostatic force (also called Coulomb’s law) is the force that operates between charges. It states that charges of the same type repel each other, while charges of opposite type are attracted together. Opposites attract, and likes repel.
The amount of force acting on two charges depends on their distance from one another. The closer two charges become, the greater the force (either pushing together, or pulling away).
Due to electrostatic force, electrons will repel or push away other electrons(-) and be attracted to protons (+). This electrostatic force holds atoms together, but it’s also the force we need to make electrons (and charges) flow.
Making Charges Flow
Every electron carries a negative charge, so if we can free an electron from an atom and force it to move, we can create electricity.
The copper atom, one of the preferred elemental sources for charge flow (used in electrical wires etc). In its balanced state, copper has 29 protons in its nucleus and an equal number of electrons orbiting around it. Electrons orbit at varying distances from the nucleus of the atom. Electrons closer to the atom’s nucleus feel a much stronger attraction to the centre than those in distant orbits. The outermost electrons of an atom are called the valence electrons, these require the least amount of force to be freed from an atom.
Applying enough electrostatic force on the valence electron – either by pushing it with another negative charge (electron) or attracting it with a positive charge (proton) – we can eject the electron from it’s orbit around the atom, creating a free electron.
Now consider an electrical wire made of copper: matter filled with countless copper atoms. The valence electron that ejected from it’s orbit is now a free electron floating in a space between copper atoms in the wire, being pulled and pushed by surrounding charges. In this chaos, this free electron eventually finds a new copper atom to latch on to; but in doing so, the negative charge of this free electron ejects another valence electron from the atom it joins! This newly ejected electron continues this cycle, on and on to create a flow of electrons called electric current.
Some elemental types of atoms release their valence electrons more easily than others. To get the best possible electron flow, we want to use atoms which don’t hold their valence electrons very tightly. The conductivity of an element is a measure of how tightly bound an electron is to an atom.
|#1||Silver||Silver is by far the most conductive metal on Earth. This is because silver only has one valence electron. This single electron is free to move with little resistance. Metals like silver and copper are a few of the metals with this particular characteristic. That is why they are great electric and thermal conductors.|
|#2||Copper||Copper (like silver) only has one valence electron – making this metal very conductive. Copper is commonly used in electrical wiring and is used to coat high quality cookware and kitchen appliances.|
|#3||Gold||Gold is resistant to corrosion and it’s high conductivity make it an extremely valuable resource, used in a large amount of industries from electronics to audio equipment.|
|#4||Aluminum||Aluminium is an excellent metal conductor. It has a low density and high resistance to corrosion, making aluminium the perfect metal for the aeronautic and communication industries.|
|#5||Zinc||Zinc is far less conductive than silver, copper, gold or aluminium. Zinc is sometimes used as less expensive and economical replacements to more conductive metals.|
|#7||Brass||Brass is far less conductive than silver, copper, gold or aluminium. Brass is sometimes used as less expensive and economical replacements to more conductive metals.|
Elements with high conductivity (weak valence electrons) have very mobile electrons and are called conductors. These conductive types of materials are used to make wires and other electrical components which enable electron flow. Metals such as copper, silver, and gold are usually our top choices for good conductors.
Elements with low conductivity are called insulators. Insulators serve a very important purpose: they prevent the flow of electrons. Popular insulators include glass, rubber, plastic, and air.
Static or Current Electricity
Electricity can take two forms: static or current. When working with electronics, we will generally be referring to current electricity, but it is important to understand static electricity as well.
Static electricity (meaning “at rest”) is created when there is a build-up of opposing charges on objects, separated by an insulator. Static electricity exists until the two groups of opposite charges can find a path between each other to balance the system out.
When static charges do find a means of equalizing, a static discharge occurs. The attraction of the static charges becomes so great that they can flow through even the best of insulators (air, glass, plastic, rubber, etc.).
Static discharges can be harmful depending on what medium the charges travel through and to what surfaces the charges are transferring.
Static charges equalizing through an air gap can result in a visible shock as the flowing electrons collide with electrons in the air, which become excited and release energy in the form of light.
A good example of static discharge is lightning. When a cloud system gathers enough charge relative to another opposite charge (be it another group of clouds or the earth’s ground) the static charges will try to equalize. As the cloud discharges, large quantities of positive (or negative) charges run through the air, causing the visible fork lightning effect we are familiar with.
Static electricity can also be witnessed in a more mundane setting when we rub balloons on our head to make our hair stand up, or shuffle our feet along a carpet and and get a shock when we touch a door handle or light switch.
Friction from rubbing different types of materials transfers electrons. The object losing electrons becomes positively charged, while the object gaining electrons becomes negatively charged. The two objects become attracted to each other until they can find a way to equalize.
With modern electronic devices, we generally don’t have to deal with static electricity, other than taking measures to avoid it. Sensitive electronic components can be damaged if they are subjected to a static discharge. Preventative measures against static electricity include wearing electrostatic discharge (ESD) wrist straps, or by including special components within the electrical circuits to protect against very high spikes of charge.
Current electricity is the form of electricity which powers all of our electronic devices. This form of electricity exists when charges are able to flow continually (as opposed to static electricity where charges gather and remain at rest).
In order for electrons to flow, current electricity requires a circuit: a closed, never-ending loop of conductive material so that electrons all have a neighbouring atom and can flow in the same general direction. If a circuit is broken, the charges cannot flow through the air, which will also prevent any of the charges toward the middle from going anywhere.
We understand how electrons flow, but how do we get electrons to start flowing in the first place? And once electrons are flowing, how do electrons produce the energy required to illuminate a light or power a motor? The answer to that we need to understand electric fields.
We understand how electrons flow through conductive matter to create electricity. Now we need to find a source to induce the flow of electrons. Most often that source of electron flow will come from an electric field.
What is a field?
A field is a tool used to model unobservable physical interactions. Fields cannot be seen, but they do have a very real effect.
The Earth has a gravitational field: the effect of a massive body attracting other bodies. Earth’s gravitational field can be modelled with a set of vectors all pointing into the centre of the planet; regardless of where you are on the surface, you feel the force pushing you towards it.
The strength/intensity of fields is not uniform at all points in the field. The further you are from the source of the field, the less effect the field has. The affect of Earth’s gravitational field decreases the further you get from the centre of the planet.
Electric fields share many similarities to how Earth’s gravitational field works, except that where the gravitational fields exerts a force on objects of mass, and electric fields exert a force on objects of charge.
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