Voltage

Author: Joe H., Inflow Engineer

In today’s post, we’re going to cover voltage, give an exact explanation of what an ohm is, and learn about Ohm’s law, which is the foundation of all electrical engineering. But first, we’re going to take one more side trip into the realms of basic physics, since we need one more concept before we can define a volt. Specifically, we need energy.

Energy, generally speaking, is the ability of something to do work. It can be stored up, or used to accomplish something. For example, if you pick up a bucket of water and raise it 1 meter into the air, you have used energy to move your hands and the bucket. However, that energy doesn’t just disappear or get burned up; in fact, the energy you used has mostly been transferred to the bucket. You could tip to bucket over and pour the water over a water wheel and the wheel would turn. When the water is moving and pushing things, we say it has kinetic energy, and when it’s sitting in the bucket waiting to be tipped over, it has potential energy. If you used the water wheel to lift up buckets full of water, you’d get a device that converts kinetic energy into potential energy and back again, at least for a little while. Eventually, your water wheel wouldn’t work anymore. The reason is that energy can take more forms than just kinetic and potential, and one of those forms is heat. As the water wheel spins, the shaft rubs against the mounting brackets, causing them to heat up. Eventually, all the usable energy is transformed into heat and dissipated into the air.

If you want to do a quick experiment at home, you can rub your hands together and feel them heat up. That heat is a form of energy and as your hands cool off the heat is transferred to the air around you. With just a simple bit of back and forth, you’ve converted the stored energy in your body into kinetic energy then into heat energy, which has then been transferred to the air around you. If you really wanted to, you could calculate how many calories you burned rubbing your hands together, since calories are a measure of potential energy stored in food.

So, what does all this have to do with electricity? Well, just like rubbing your hands together converts kinetic energy into heat, when electrons flow through a wire they emit a certain amount of heat. We measure this heat in joules (J), which is a unit of energy equal to about 0.00024 calories. A volt (V) is a measurement of potential energy, specially, it’s the amount of electrical potential energy needed to generate 1 J of heat in one second by moving 1 amp (A) worth of current [1]. In plain English, a volt is a measurement of how hard electrons are pushed through a wire by a given power source. The higher the voltage, the harder electrons can be pushed through a wire.

Now that we know what a volt is we can give an exact definition of an ohm (Ω). Remember, the atoms in a wire try to hold onto the electrons as they pass, limiting the amount of electrons that can flow through a wire at any given time (resistance). With a higher voltage, you can push more electrons through the wire. The Ω is the unit we measure resistance in, and it’s defined at the amount of resistance which allows 1A of electrons to flow through a wire when 1V of power is applied. We can write this relationship as 1Ω=1V/1A.

The really cool thing about this definition is that because an Ω is a relationship between voltage and current, we can always find the resistance in a wire if we know the voltage and current, or find the current if we know the voltage and resistance, or find the voltage if we know the resistance and current. If we use the letter R to represent any resistance, the letter I to represent and current, and the letter V to represent any DC voltage, we get the following general relationship: V=IR. This relationship is known as Ohms law, and as I said in the first paragraph, it’s the foundation of all electrical engineering. With Ohms law, we can go back to our lightbulb example from last week, and instead of just guessing at how much resistance we need to make sure that the bulb doesn’t burn out, we can calculate an exact value. For instance, if our bulb needs exactly 0.5A of current to function, and our power source is 9V, then we need 18 Ω of resistance in our device.

Now that we have most of the basics covered, we’re going to start looking at some simple electrical components and circuits. We already touched on resistors briefly in the last post, but they’ll be coming up again in the next post, along with some of the basic laws for working with circuits. One more important note, you’ll notice that when I gave you Ohms law, I specified that the voltage is DC, or direct current. This is because alternating currents create some interesting effects when they flow through wires. Current and voltage are the same, but instead of resistance, we get something called impedance. It’s a little more complicated and so in order to give you some time to get familiar with the basics, we’ll be limiting ourselves to working with DC based circuits for several posts. That’s it for this post, be sure to check back soon for the next one!

[1] For those of you who like math, the relationship can be given as 1 V= 1J/(1A*1s)

 

At Inflow we solve complex terror and criminal issues for the United States Government and their partners, by providing high quality and innovative solutions at the right price through the cultivation of a corporate culture dedicated to being #1 in employee and customer engagement. We Make it Matter, by putting people first! If you are interested in working for Inflow or partnering with us on future projects, contact us here

Resistance

Author: Joe H., Inflow Engineer

Now that we’ve covered how we generate usable electricity, we need to go over what happens when trillions of electrons are pushed through a wire in a fraction of a second. To do so, we have to go back to our old friend, the atom. Atoms have charged particles called protons in their centers, which are attracted to electrons. When electrons move into a wire, they are captured by the protons in the wire’s atoms. As more and more electrons are pushed into one end of the wire, the wire runs out of protons to capture electrons. If we keep trying to push electrons into the wire, one of two things is going to happen…

The first option is the atoms hold on to the electrons they already have. When this happens, the electrons being pushed into the wire have no place to go and stop moving down the wire. In this case, no current flows. Materials that do not let electrons flow are called insulators. While this might sound boring, it’s actually a very important phenomenon. For example, the plastic coating on your computer’s power cable keeps you from electrocuting yourself when you plug it in and it ensures that your computer gets the correct amount of power to operate. This principle was beautifully illustrated recently at CERN, when a small mammal chewed through a power cable and disabled the whole machine. [1]

The second option is the atoms in the wire will give up the electrons they’ve already captured and accept the new electrons. These released electrons will then travel further down the wire, propagating the current through the wire. Obviously, if we want to do anything with electrical currents, this is the type of behavior we want. Materials that allow electrons to flow freely like this are called conductors. However, in most materials, the atoms don’t just release their electrons without a fight. Much like trying to pull two magnets apart requires a bit of work, a certain amount of force is needed to push the electrons away from their atoms. This tendency of electrons to stick to atoms is called resistance. We can measure this tendency and use the unit Ohms (Ω) to describe how much resistance a material has. [2]

All normal conductors have some small level of resistance; the rare materials that have no electrical resistance at all are called super conductors (we’ll talk about these perfect conductors in a later post). Interestingly, there’s no such thing as a perfect insulator; with enough effort you can push electrons through a normally non-conductive material. However, if we know how much force (which we call voltage) is being applied to the electrons we’re using, we can pick materials that are very conductive and surround them with materials that do not conduct at the voltage we’re using. There’s one more piece to the puzzle though: materials that have more resistance than just a normal wire, but not enough resistance to completely prevent the flow of electrons at a given voltage. We call components that exhibit this “in-between” level of resistance resistors, and they are incredibly useful items.

Resistors let us manipulate the amount of current flowing through a section of wire. At a given voltage, the more resistance we have, the fewer electrons will flow through. Remember in the last post, where I gave the example of a lightbulb burning out if too many electrons flow through it at once? With a resistor, we can reduce the amount of current the lightbulb gets. When we’re using batteries, which can only provide so many electrons before going dead, limiting the current to the bare minimum needed makes our batteries last longer. There are even some materials which change their resistance under certain conditions. A light dependent resistor, for example, decreases its resistance when exposed to light. Want a coffee maker that turns on when the sun rises? Use a light dependent resistor and you can make one. As we move forward, we’re going to see many more uses for resistors.

You may have noticed that I did not give an explanation of exactly what an ohm is, unlike the last post, where we talked about amps. That’s because we define that value of 1 ohm in relation to both current and voltage, so we need to talk about voltage in a bit more detail first. We’ll do that in the next post and then look at how current, voltage, and resistance are all related. This will lead us to Ohm’s law, one of the fundamental tools of electrical engineering. We’re just starting to get to the interesting part, so be sure to check back for the next post.

[1] http://phys.org/news/2016-04-weasel-large-hadron-collider.html

[2] Named after Georg Ohm, who first published research on the topic. https://en.wikipedia.org/wiki/Georg_Oh

 

At Inflow we solve complex terror and criminal issues for the United States Government and their partners, by providing high quality and innovative solutions at the right price through the cultivation of a corporate culture dedicated to being #1 in employee and customer engagement. We Make it Matter, by putting people first! If you are interested in working for Inflow or partnering with us on future projects, contact us here

Power Generation

Author: Joe H., Inflow Engineer

In the last post, we talked about what electricity is. As a quick refresher, there are tiny charged particles called electrons, and electricity is the movement of these electrons. In this post, we’re going to look more closely at the relationship between electricity and magnets, and how magnets can be used to generate electrical currents. We’ll start with a closer look at magnets and something called electromagnetic fields.

Almost everyone has played with magnets at some point in their life. Every magnet has two ends, typically labelled N and S. If you take one of these magnets and place it in a pile of iron filings, the iron filings will move themselves around into the pattern as seen in Figure 1.

Figure 1: Magnetic Field

These lines are a physical manifestation of the electromagnetic field that exists between the N and S ends of the magnet. This field is caused by the arrangement of electrons (and the atoms they’re attached to) within the magnet. Field theory is a very complex topic, but for our purposes we can think of them as the lines along which a force moves. A force is anything that pushes or pulls something else. For example, gravity is the force that pulls objects with mass together [1]. The force that we’re interested in here is the electromagnetic force, which is the force which pushes and pulls charged particles.

In the case of magnets, the electrons in the iron filings are pulled into alignment with the field lines by the electromagnetic force, pulling the filings along with them. Any time you have an electromagnetic field and you put electrons in that field, the electrons will be pushed into alignment with the field by the electromagnetic force. Since electrons move to align themselves with these types of fields, when you move an electromagnetic field across a metal wire by moving the magnet generating the field, the electrons in that wire will move just like the electrons in the iron filings. If the wire isn’t allowed to move with them, the electrons will move from atom to atom in an attempt to align with the field, causing a uniform flow of electrons in one direction within the wire. This movement will in turn displace other electrons in the parts of the wire not placed into the electromagnetic field, causing an electrical current to move down the whole length of the wire. If the ends of the wire are disconnected, there’s nowhere for the electrons to go, but as soon as the ends are connected, the current will be able to flow freely. When you move the magnet in one direction, the current will flow in one direction, and when the magnet moves back in the other direction, the current will flow in the opposite direction. Imagine a tube filled with metal marbles, connected to form a circle. If you move a magnet along the tube, all the marbles will move, while the tube itself will remain stationary. In the same way, we generate electrical current by spinning magnets (using a steam turbine or water turbine for example) within wire loops, as shown in Figure 2.

Figure 2: Basic Generator [2]

All the electricity we use in our modern world is generated this way. There are other natural phenomena which can create electrical currents, such as static electricity, but they don’t create consistent, controllable currents. By using magnets, we can make electrons move in predictable, consistent ways. If you have a magnet of a given strength and you spin it at a consistent speed inside a specific wire loop, you will always get the same number of electrons moving. This is important if we’re trying to design a device that does certain things based on how many electrons are flowing through it. For example, a light bulb connected to an inconsistent power source will flicker out if it does not receive enough electrons and could burn out if it receives too many electrons.

So now we have established a way to move a specific number of electrons at a given speed, we can use batteries to store these electrons for later use or we can start designing things that use those electrons to do something. The first thing we need in order to do this type of design is a way to describe how many electrons and therefore how much current is moving across an area. The unit we use is amperes or amps. One ampere is approximately 6,242,000,000,000,000,000 electrons worth of charge moving past a point per second. In the next post, we’re going to look at what happens when you push that many electrons through a wire, so be sure to check back for that!

 

Sources Cited

[1] Technically, gravity bends spacetime itself, but that’s outside the scope of this post series. For more on gravity from a general relativity perspective, check out this video from PBS Space Time.

[2] By Egmason - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=1025045

 

At Inflow we solve complex terror and criminal issues for the United States Government and their partners, by providing high quality and innovative solutions at the right price through the cultivation of a corporate culture dedicated to being #1 in employee and customer engagement. We Make it Matter, by putting people first! If you are interested in working for Inflow or partnering with us on future projects, contact us here

Electrical Engineering for Everyone

Author: Joe H., Inflow Engineer

This post is the start of a multi-part series on electrical engineering specifically geared towards people with absolutely no science, engineering, or math background. As long as you know how to read, you should be able to follow along. We’re going to start by focusing on what electricity is, how it’s created, and how it behaves in certain situations. We’ll come back the engineering aspect once we’ve covered those basics.

To start off, we need to talk about what matter is made of. Let’s start with a piece of pure copper. If you take that piece and cut it in half, you get two smaller pieces, but both are still copper, and have all the same physical properties. Cut one of those pieces in half again, and the results will still be copper. However, if you keep cutting your copper into smaller and smaller pieces, you’ll eventually reach a point where you have the smallest bit of copper possible. That tiny piece is called an atom, and if you split a copper atom into pieces you no longer have copper. Instead, you have a collection of three types of particles, protons, neutrons, and electrons. In every atom, the protons and neutrons are lumped together in the center (nucleus) of the atom, while the electrons orbit around the outside. This figure shows a very simplified version of how atoms are put together, with protons shown in red, neutrons in black, and electrons in blue. Every atom in the universe is made up of these three particles in different combinations. For instance, a copper atom has 29 protons, 35 neutrons, and 29 electrons, while an iron atom has 26 protons, 30 neutrons, and 26 electrons.

One thing that may have caught your eye in those two example atoms I just listed is the fact that the number of protons in each atom is the same as the number of electrons. This is not a random coincidence. Protons and electrons are charged particles. Protons have a positive charge and electrons have a negative charge, so the two types of particles are attracted to each other, in much the same way that two magnets are attracted to each other. Because electrons are not attached to the nucleus of the atom they can (under the right circumstances) move from one atom to another. When this happens, the atom which has lost its electron becomes positively charged and is called an ion. Atoms can also have an extra electron forced into orbit around them, which gives the atom a negative charge, and is called an anion. Ions will readily accept electrons and anions will readily give up their extra electrons. As a result, you can have a whole pile of atoms with electrons moving between them. This movement of electrons is called electricity.

In order for electricity to be useful, you need a lot more than one electron moving and you need all of those electrons to move in one direction. Conveniently, because they are charged particles, when you move a string of electrons through a wire, they generate a magnetic field, and when you move a wire through a magnetic field, it causes the electrons in the wire to move together in one direction. This is called an electrical current. When you move a wire back and forth through a magnetic field, the electrons will flow in one direction and then the other. In fact, that’s exactly how the electricity coming out of your wall outlet is created. Because the electric current flows first in one direction and then back in the other direction, this type of electricity is called alternating current, or AC. Most of your large household electronics (lights, air conditioners, refrigerators, etc.) use this type of current. With a little bit of trickery, which we’ll cover later, you can also take electrons moving back and forth and make them move consistently in one direction. This is known as direct current or DC, and can be stored in batteries, another topic we’ll look at in another post. Because of this, DC electricity is used in computers, televisions, mobile phones, and other small electronic devices.

In both AC and DC based devices, the electrons flow through wires and special components to cause very specific reactions. As a simple example, a lightbulb is a thin coil of wire which glows when electrons pass through it. As the electrons are accepted and given up by the atoms in the wire, the atoms begin to vibrate, generating heat and light. An air conditioner, on the other hand, uses the movement of the electrons through its internal wires to create magnetic fields, which turn fans and drive compressors and pumps. The screen you’re reading this on uses resistors, capacitors, transistors, and LEDs to emit certain colors at different points on the screen. We’ll be looking at all these items and more in detail as we go through this series.

Hopefully, the concepts we’ve covered today make some degree of sense to you. I’ve simplified them quite a bit, especially with regards to atoms, so if you want to dig deeper into that subject, there’s a good primer on the development of modern atomic theory at How Stuff Works. We’re going to look at how electricity is generated in more detail in the next post, so be sure to check it out!

 

At Inflow we solve complex terror and criminal issues for the United States Government and their partners, by providing high quality and innovative solutions at the right price through the cultivation of a corporate culture dedicated to being #1 in employee and customer engagement. We Make it Matter, by putting people first! If you are interested in working for Inflow or partnering with us on future projects, contact us here