Electrical Fundamentals Module #1 – The Groundwork
You’ve probably been wondering when we were going to finally switch it up a little, get away from that nasty steam and HVAC stuff. We’ll get back to it soon enough as those are both huge parts of building engineering. Everyone has their strengths and electricity is not one of mine lol.
I discovered this electrical fundamentals book that lays out the basics first and then eventually gets into circuits, motors, and controls and more.
This first post for the fundamentals of electricity is going to set up our foundation of electrical terms,
definitions, and concepts. Having a good handle on these will only help us all later on when we get into
things like motor or circuit troubleshooting (really one of my weak points.)
Later we will lay out some basic definitions of electrical terms like voltage and resistance but first let’s
discuss what an electrical charge is.
Electrical Fundamentals – Basic Terms & Definitions
Before we get into the first section of defining an electrical charge, let’s remember back to one of our first engineering fundamentals posts where we talked about matter, molecules, and atoms.
We all have heard about atoms; they have a nucleus made up of protons and neutrons and then skirting around the outside in an orbit (like the solar system sort of,) are electrons.
What is an Electrical Charge?
We all know opposites attract right?
A material that either attracts or repels another charged material has an electrical charge. The charge isn’t always just negative, it can be positive too.
If you have ever played around with magnets, you’ve seen this concept in action. Two materials with positive charges will repel each other, as will two objects or materials both with negative charges. When we have two materials with opposite charges, one negative and one positive, they attract.
If you try to force two magnets together at their positive poles, or the negative poles, they try to push
the other away. Flip one around and snap snap, they stick together.
Inside the Atom
The atoms of different elements have different numbers of protons, neutrons, and electrons from one another. Inside the nucleus of an atom are the protons and neutrons.
Protons hold positive charges, they attract electrons. Neutrons have no charge and are electrically neutral. Neutrons don’t attract or repel anything, poor little lonely fellows.
Electrons have a negative electrical charge and are also much lighter in mass than protons. Electrons orbit or revolve around the nucleus of the atom continuously. In an atom, there are an equal number of protons and electrons. By looking at the periodic table of elements you can tell how many of each make up an atom of that element.
Electrical current is a flow of electrons. Electrons in motion create electrical current. In your home for
example, current flows through the wiring hidden behind the walls. This wiring, also called a conductor, is usually made of copper right?
So we have this long stand of wire made up of who knows how many atoms of copper. In every single copper atoms, we have 29 protons and also 29 electrons. In every single copper atom, those 29 electrons are zipping around the nucleus in orbit.
If we then apply some sort of pressure, in this case electrical pressure (more on this in the voltage
section,) the electrons are forced out of their orbiting paths and they get passed along, copper atom to
copper atom through the length of the conductor.
The more electrons getting passed along, the more current. The unit of measurement for current is the
ampere, or amp. We use the letter ‘I’ to represent current.
For this post, we are only concerned with two types of current, ac and dc. AC, alternating current, is a
current that fluctuates, it changes direction and intensity at set intervals. This is usually what your home is supplied with. DC, direct current, is the opposite. It’s a straight shot of current, one direction, all the time. This current you see in batteries and is used to run the headlights in your car.
We can’t have the flow of electrons, or current, without something driving them. This driving force is
called voltage. It supplies the electrical pressure necessary to move the electrons along the conductor. In order to move them, we need a closed circuit and some amount of voltage.
We can get this from batteries, power plants, or generators. The unit of measurement for voltage is the volt and this book says it is represented by ‘E.’ I have always used ‘V,’ and you will see that often.
Not every material likes helping out the flow of electrons, some things don’t make good conductors. Like wood for example. Copper is awesome, copper atoms offer very little resistance to the flow.
The property of an object or material that opposes this flow is called resistance. Everything has some
amount of resistance, some a lot, some very little. The good ones we use as conductors, the bad ones are called insulators – rubber, wood.
Resistance is measured with the ohm and use the Greek omega as its symbol. For equations, just use the letter ‘R.’
Let’s talk about batteries real quick and how polarity ties in. Polarity is defined as, well it’s not really
defined, it uses itself to define itself, 1) the property of having poles or being polar, 2) the relative
orientation of poles; the direction of a magnetic or electric field.
All dc sources, batteries and the like, have two terminals. These terminals have electrical polarity. You’ve probably noticed when replaces the batteries in a device the plus and minus symbol. One is the positive terminal, the other is the negative terminal.
Electrons flow from the negative terminal to the positive side. This is why the negative wire on your car
battery is the one you must be careful of especially. If you touch that and you’re grounded, you have just become the positive terminal.
We’ve talked a little about Ohm’s Law in the engineering fundamentals sections. Once more though, Ohm’s Law states that in an electrical circuit:
- the current is directly proportional to the voltage applied to the circuit and
- is inversely proportional to the resistance in the circuit.
Voltage and resistance both impact current. If we have this massive amount of voltage trying to create this electrical pressure but we have a poor conductor, more like an insulator, we won’t have a flow of electrons so no current.
Using Ohm’s Law
If we were to hold the resistance in a circuit constant, we can alter the current by changing the voltage. Increase in voltage equals increase in current. If we keep the voltage constant but lower the resistance, current will increase. The electrons are getting the same electrical pressure force behind them but having to work less to move in a good conductor. Ya dig?
You should now have quite the handle on the basics of electricity.
Once again, we are starting with the building blocks of everything and talked about the components of an atom – the protons, neutrons, and electrons.
An atom has the same number of protons as electrons. The electrons are constantly spinning around the nucleus in orbit like a planet. Using an electrical pressure, voltage, we can knock the electrons out of their normal orbit paths into the next one. This movement of electrons is called current.
If the material is not all keen on helping out the movement, it is not a good conductor and would probably make a better insulator. This is measured through resistance.
And then finally, we covered polarity and Ohm’s Law. Electrons always flow from negative to positive, kind of like how heat is transferred from warmer to cooler. Ohm’s Law helps to define the relationship between voltage, current, and resistance.
If you have any questions, corrections, or comments, let’s hear them. If you would like to contribute, let’s talk about that too.