Electricity and how it works
Electricity is a natural phenomenon that occurs throughout nature and it takes different forms but for purposes of this tutorial, we’ll only concentrate on current electricity i.e. what powers our gadgets. The goal here is to understand how electricity flows from a power source through wires, spinning motors and powering our gadgets.
We see its everyday application when we use it to power our devices like smartphones, computers, lights, home appliances etc, but its more than what keeps appliances turned on and off.
In this tutorial, we are going to cover the following:
- What Electricity is.
- What an atom is and it’s building blocks
- Flow of charge
- Static & Current electricity
- What an electric field is
- Electric Potential Energy & Electric potential
- A look at an electric circuit
What is Electricity?
Basically, it’s the flow of electric charge but there is so much behind this brief description, so many questions to be answered, for example; where do the charges come from?, how do we move them?, where do they move to?, how does an electric charge cause mechanical motion or how does it make things light up?
To begin to explain what electricity is, we need to dig way deeper beyond the matter and molecules, to the atoms that make up everything we interact with in our everyday life.
What is an Atom?
Basically this is the smallest component of an element that contains the chemical properties of that element. Atoms are one of the basic building blocks of life and matter and they exist in over a hundred different forms as chemical elements like hydrogen, carbon, oxygen and copper. The atoms combine to make molecules which build the matter we can physically see and touch.
The atom alone cannot explain how electricity works, we need to move down one more level and look at the building blocks of atoms.
Building blocks of an Atom:
The atom is built with a combination of three distinct particles ie Electrons, Protons & Neutrons. Each atom has a center nucleus where Protons & Neutrons are densely packed together surrounded by a group of orbiting electrons. Consider a very simple atomic model below.
Fig 1. The basic structure of an atom.
The Atomic Number (the number of protons), defines the chemical element the atom represents. For example an atom with just one proton is hydrogen, and an atom with atomic number 29 (ie 29 protons) is copper. So basically everything is made up of tiny atoms, and looking at the atomic model we see that:
Protons are positively charged (carry a positive charge)
Electrons are negatively charged (carry a negative charge) and
Neutrons carry no charge.
Flow of Charge:
Earlier, we defined Electricity as the flow of electric charge. Charge is a property of matter and just like volume and mass, it can be quantified and measured. The key concept here is that charge comes in two types, positive and negative and in order to move charge, we need charge carriers and this is where our knowledge of charge carriers comes in handy.
From the atomic model, we’ve seen that Electrons carry a negative charge, Protons carry a positive charge whereas Neutrons are neutral with no charge. We should note that Electrons and Protons carry the same amount of charge, just a different type. The charge of both Protons and Electrons is very important because it provides us the means to exert a force on them.
The force that operates between charges is called Electrostatic Force (Coulomb’s Law) which states that “charges of the same type repel each other while charges of opposite type are attracted to each other.”
Fig 2. Illustration of Coulomb’s Law
Just like in magnets with North and South poles, like sides repel and unlike sides attract. The same similar thing happens at the atomic level, the electrons and protons are attracted to one another but only electrons are able to move from one atom to another.
If there is the same number of electrons and protons, there is balance, but if there is an excess of electrons, they’ll do their best to move to the nearest atom that has fewer electrons, always trying to find balance. This is how electrons flow and this chain effect can continue in an endless loop to create a flow of electrons called Electric Current.
Fig 3. A simplified model of charges flowing through atoms to make current.
An element’s conductivity measures how tightly bound an electron is to an atom. Elements with high conductivity containing very many electrons are called Conductors. These are the types of materials we use to make wires and other components that aid in electron flow. Examples of good conductors are copper and gold. Elements with low conductivity are called Insulators and they serve a very important purpose i.e. they prevent the flow of electrons, examples of insulators are glass, rubber, plastic and air.
Difference between Static and Current Electricity:
Electricity can take two forms i.e. Static & Current. When it comes to electronics, current electricity will be more common, but we also need to understand static as well.
This is a result of an imbalance between positive and negative charges in an object. The charges can build up on the surface of an object and they find a way to be released/discharged. When the opposite charge finds a means of equalizing, a “Static discharge” occurs. The attractions of the charges becomes so great that they can flow through the best of insulators i.e. air, plastic, rubber, etc. A good example of static discharge is “Lightning”.
When working with electronics, we generally don’t deal with static electricity, but on rare cases, when we do, we’re just trying to protect our sensitive components from being subjected to static discharge. We prevent this by wearing an ESD (Electrostatic Discharge) wrist strap, or adding special components in circuits to protect against very high spikes of charge.
This is a form of electricity that runs all of our electronic devices. It exists when charges are able to flow constantly as opposed to static electricity where charges gather and remain at rest. It’s dynamic and charges are always on the move. This is the form of electricity that we’ll be focusing on for the rest of this tutorial. In order to flow, current electricity requires a circuit, a closed never-ending loop of conductive material. We shall talk more about circuits in the next chapter.
At this moment, we’ve so far covered how electrons can flow, but then we need also to look at how we get them flowing and how they produce the energy required to illuminate light bulbs or spin motors. For this therefore, we need to understand the concept of electric fields.
Now that we know how electrons flow through matter to create electricity, we need a source to induce the flow of electrons and that source of flow will come from an electric field. An Electric Field is basically a field space around a charged particle where its force (vertical force) can be experienced by any other charged particle.
Electric fields are an important tool in understanding how electricity begins and continues to flow i.e. they describe the pulling and pushing force in a space between charges. For an electric field of a single charge, the positive charge has an outward electric field pushing away like charges and the negative charge has an inward electric field because it attracts positive charges as illustrated below.
Fig 4. An illustration of an Electric field
Electric Potential Energy
When we use electricity to power our circuits and gadgets, we’re transforming energy. Electronic circuits must be able to store energy and transfer it to other forms like heat, light, or motion and the stored energy of a circuit is called Electric Potential Energy. This energy describes how much stored energy it has when set in motion by an electrostatic force and that energy can become kinetic and the charge can do work.
Electric potential basically builds up on electric potential energy to help define just how much energy is stored in electric fields. At any point in an electric field, the E.P is the amount of E.P.E divided by the amount of charge at that point.
In any electric field, there are two points of interest i.e. the point of high potential where a positive charge would have the highest possible P.E and the point of low potential where a charge would have the lowest possible P.E.
Fig 5. Electric Potential Energy
N.B: The most common term we discuss when evaluating electricity is Voltage. This is basically the difference in potential between two points in an electric field and it gives us the idea of just how much pushing force an electric field has.
By now we’ve covered how electricity works and we have all the necessary requirements to make current electricity. So let’s try to see how it works in a circuit.
A look at an electric circuit
With what we’ve learnt so far, about particle physics, field theory and potential energy, we now know more than enough to make electricity flow.
A short circuit:
Consider the simple circuit below;
Fig 6. A short circuit
The circuit above consists of a single battery and a conductive wire. Batteries are a common energy source that converts chemical energy to electrical energy. They have two terminals (positive & negative) that connect the rest of the circuit. One terminal has an excess of negative charges while all of the positive charges concentrate on the other. This means that there is an electric potential difference just waiting to act.
When a copper wire is connected from one end of the battery to another, the electric field will influence the negatively charged free electronics in the copper atoms and pulled by the positive terminal as shown above. Here the electrons in the copper will move from atom to atom creating the flow of charge we know as electricity.
In such a short circuit, energy produced by the current flowing is too much, especially since there’s nothing in the circuit to slow down the flow or consume the energy. Too much energy here will turn into heat energy in the wire which may quickly turn into melting the wire or cause a fire.
N.B Connecting a pure conductor directly across an energy source is a very bad idea.
A Complete Circuit:
Consider illuminating a light bulb
For this case, let’s try and build a rather complete circuit that actually does something useful instead of wasting all the energy as we’ve seen in the earlier short circuit.
Let’s consider the circuit below;
Fig 7. A complete circuit
If we connect a light bulb to the battery with wires in between, we have a simple, functional circuit and this generally means an electric circuit will transfer electric energy into some other form i.e. light, heat, etc.
In the circuit above, a battery is connected to a light bulb and the circuit is completed when the switch is closed. With the switch closed, the circuit is complete and electrons throughout the circuit are influenced and subjected to an electric field.
All the electrons in the circuit start flowing at seemingly the same time from the negative terminal of the battery through the light bulb where they will transform energy from electrical to light (heat) to illuminate the bulb and then finally to the positive terminal.
In this tutorial, we’ve learnt the basics of electricity and how it works, we now know all about electric fields, how electrons flow and how to make them flow. In our next tutorial we are going to cover Circuit Basics in more details.