# ATAT 105 Basic Electricity > # [[T105 Intro| ◀️ ]] &nbsp;[[T105 Home| Home ]] &nbsp;[[T105 Week 2| ▶️ ]] &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [[QR T105 Week 1| 🌐 ]] ># [[T105 Week 1|Week 1]] >- [[T105 Week 1#Atomic Structure|Atomic Structure]] >- [[T105 Week 1#Types of Electricity|Types of Electricity]] >- [[T105 Week 1#Units of Measurement|Units of Measurement]] ># [[T105 Week 1#Lab|Lab]] >- [[T105 Week 1#! T105L SAFETY Safety Briefing|Safety Briefing]] >- [[T105 Week 1#A Basic Circuit|A Basic Circuit]] >[!jbplus|c-blue]- Lesson Intro >### What > >In this lesson you will learn some fundamental concepts about [[electricity]] to prepare you to understand [[circuit]]s. > >### Why > >A basic understanding of electricity is important for any aviation technician as electrical circuits are everywhere in aircraft, and all technicians, even if they do not actually repair electrical equipment, must be able to operate professionally and safely where electricity is concerned. You will use this knowledge throughout your aviation career. > >### Testing > >You will be tested on this material on Assignment 1, the Midterm, and the Final Test, as per the [[T105 Intro#Testing and Grades|testing strategy]]. >[!jbplus|c-blue]- Prof >### Objectives > >This week is all about orientation and familiarization. > > ### Theory >For the theory classes, use of the SSG and exploitation of the supports available are key. How you will run attendance, and other daily activities are up to you. The course intro should make the route clear for the duration of the course. >### Lab >For the lab, a thorough safety briefing and orientation in the labs, including how we will distribute the training aids etc. is important and sets the tone for the rest of the course. PPE is a hard and fast requirement, and students should be warned that beginning Week 2, incorrect PPE may result in missing the lab and the associated attendance. The experiment in class is simply meant to get them used to the benches and training aids, and to pique student curiosity. Do not go too deeply in explaining what they will see. This week should leave them with some unanswered questions which will become more clear in the coming weeks. ==This material is reviewed in [[V208 Week 1]]. Test questions are shared between the two.== ## Atomic Structure Generally, when students have difficulty with this material, it is because they are not used to having to form images in their mind which aid understanding. We cannot show you an atom in class, nor can we show you an electron moving from one molecule to another. This of course is because we are dealing with things smaller than the human eye can detect. But even if we could see them, it may not help us to understand. For this reason, you will be presented with graphics of different types, none of which are accurate physical representations, but which are intended to illustrate concepts. They are cartoon versions of the physical processes we are studying. When learning this material, be patient as you form your own mental picture of what is happening, and be open to the different types of graphics, as some may resonate better with you, or make things clearer. In a similar way, be open to different explanations of these matters, whether it is in the course, or in the textbook, or on the internet. Some descriptions may be much easier for you to digest than others. ### Matter > [!aside]- Ref > [[AMT General Handbook Ch5_1#Matter|📘]] Let's make sure that we understand a few key terms before moving on: [[Matter]] is the material that makes up our universe. It occupies space, it has weight (or more correctly, mass), and can be in the form of solid, liquid, or gas. You may see plasma added to this list; as our knowledge increases, the explanations expand! Let's drill down a layer, or zoom in, depending on which analogy suits you. #### Compounds [[Chemical Compound|Compounds]] are combinations of two or more [[element]]s. When two elements combine to make a compound, an entirely different material will result. In other words, if you were to divide a compound again and again, you would ultimately arrive at… #### Elements An [[element]] is a substance that cannot be separated into different substances (like we just did with [[compounds]]). They can exist by themselves, like for instance copper, hydrogen or carbon. Or, as we've seen, they can combine to form compounds, such as water, which is made up of the elements hydrogen and oxygen. #### Molecules > [!aside]- Ref >[[AMT General Handbook Ch12_1#Molecule|📘]] %%==[[Master QB1#Q00432|Q]]==%% [[Molecule]]s are combinations of two or more atoms. Molecules can both be compounds (eg. water, or H$_2$O) and elements (eg. hydrogen, or H$_2$). Once again, we will zoom in or drill down to… ### Atoms > [!aside]- Ref > [[AMT General Handbook Ch12_1#Atom|📘]] %%==[[Master QB1#Q00418|Q]][[Master QB1#Q00425|Q]][[Master QB1#Q00435|Q]]==%% Atoms are the smallest particle that an element can be divided into and still retain the properties of the element. It consists of a nucleus and orbiting electrons. Now, before we go into atoms, let's reverse the dividing process to make sure we understand this underlying structure: - Like atoms - molecules of elements - Different atoms - molecules of compounds Atoms combine to form molecules. Like atoms combine to form molecules of elements. Different atoms or elements combine to form molecules of [[Chemical Compound|compounds]].  [[Faculty/Student/Content/ATAT/T105/assets/images/Pasted image 20210515132949.png|➡]] #### Three Sub-particles > [!aside]- Ref >[[AMT General Handbook Ch12_1#Electrons Protons and Neutrons|📘]] %%==[[Master QB1#Q00452|Q]][[Master QB1#Q00454|Q]][[Master QB1#Q00443|Q]][[Master QB1#Q00919|Q]]==%% Atoms are composed of three sub-particles: protons, neutrons and electrons. The nucleus contains protons and neutrons. Electrons orbit the nucleus. - **Neutrons** have no electrical charge, or could be referred to as having a neutral charge. - **Protons** have a positive electrical charge. - **Electrons** have a negative charge. Electrons are very small. The mass of a proton is almost 2000 times as much.  [[Faculty/Student/Content/ATAT/T105/assets/images/Pasted image 20210515133609.png|➡]] #### Atomic Number %%==[[Master QB1#Q00427|Q]][[Master QB1#Q00441|Q]]==%% There are the same number of protons in the nucleus as electrons orbiting the nucleus. The charges in a normal atom are equal and opposite so they cancel each other out, meaning that an atom is a neutrally charged particle.  [[Faculty/Student/Content/ATAT/T105/assets/images/Pasted image 20210515134238.png|➡]] The atomic number of an atom refers to the number of protons in that atom. The elements in the periodic table are arranged in order of their atomic number. Since the periodic table lists neutral atoms, the atomic number also tells us the number of electrons. Why do we specify a neutral atom? Because this balance can be disrupted, leaving an atom with a positive or negative charge. When this happens, we refer to it no longer as a neutral atom, but as an ion. If the overall charge is positive, that is, the atom is missing one or more electrons, leaving the atom positively charged, it is called a positive ion.  [[Pasted image 20210811200736.png|➡]] Conversely, if an atom has an extra electron, it is called a negative ion.  [[Pasted image 20210811201056.png|➡]] ### Electrons  [[Faculty/Student/Content/ATAT/T105/assets/images/Pasted image 20210515134123.png|➡]] ##### Orbit > [!aside]- Ref >[[AMT General Handbook Ch12_1#Electron Shells and Energy Levels|📘]] %%==[[Master QB1#Q00445|Q]]==%% The circular path along which electrons travel around the nucleus of an atom is called an orbit or shell. These shells are designated by either letters or numbers. For our purposes, it doesn't matter. We are mostly interested in the outside shell, whatever its letter or number. For the simplest atom, Hydrogen, there is one electron in orbit. As we add electrons and their balancing protons in the nucleus, they orbit together. As each orbit fills up, another is created, farther from the nucleus. These orbits each have a capacity, and once full, the atom is very stable. It is when an orbit is something other than full that instabilities in an atom present themselves. ##### Valence shell and valence electrons > [!aside]- Ref > [[AMT General Handbook Ch12_1#Valence Electrons|📘]] %%==[[Master QB1#Q00442|Q]][[Master QB1#Q00458|Q]][[Master QB1#Q00887|Q]]==%% The outermost orbit (shell) of an electron is known as the valence orbit. Electrons in the valence orbit are known as valence electrons. The force of attraction between the positive charged nucleus and the negatively charged electron decreases with increasing distance. This means that electrons in orbits farther from the nucleus are less tightly bound to the atom than those closer to the nucleus.  [[Pasted image 20210811212829.png|➡]] This graphic shows a copper atom, which consists of 29 positively charged protons, and 29 negatively charged electrons in orbit. We can ignore the neutrons for our purposes. Because the electrical charges of the protons and the electrons are balanced, this atom is said to be neutral, and is electrically balanced. ##### Free Electrons > [!aside]- Ref >[[AMT General Handbook Ch12_1#Free Electrons|📘]] %%==[[Master QB1#Q00440|Q]][[Master QB1#Q00438|Q]][[Master QB1#Q00426|Q]][[Master QB1#Q00437|Q]][[Master QB1#Q00450|Q]][[Master QB1#Q00873|Q]][[Master QB1#Q00874|Q]][[Master QB1#Q00911|Q]][[Master QB1#Q00912|Q]]==%% Certain elements, chiefly metals, are known as conductors because an electric current will flow through them easily. Common examples would be gold, silver, and copper. These conductive elements have a valence orbit that is nearly empty. This, and the effect of the distance from the nucleus means that valence electrons are easily given up or received from one atom to another. As mentioned a moment ago, if energy is applied to these kinds of atoms, the electron can be dislodged from the valence shell. It can gain sufficient energy to jump the gap from the valence band to the conduction band. It then becomes a free electron. This has a number of effects. The atom that lost its valence electron has lost its negative charge as well. Now, instead of a neutral overall charge for the atom, the atom is left with an overall positive charge, changing it to a positive ion. The hole that is left represents a positive charge. The electron that is now moving outside of its atom is negatively charged. Remembering that like charges repel, and unlike charges attract, we now have electrical forces in play. The free electron is attracted to positive ions, that is, atoms that are missing the valence electron, and the now positive atoms are similarly attracted to the negatively charged free atoms. This causes the electrons to move, and is known as [[Electricity]].  [[Pasted image 20210821081247.png|➡]] This chain reaction of electrons being pushed out of the valence orbit and becoming free electrons that are attracted to the holes left by other vacating electrons is how current flows. Note that we are not describing an electron that travels the length of these atoms. It may appear that way, but it really is made up of many electrons making much shorter trips:  Before we go deeper into electrical current, let's finish off our look at atomic structure by looking at two categories of material from an atomic perspective. ### Conductors and Insulators #### Conductors > [!aside]- Ref > [[AMT General Handbook Ch12_1#Conductors|📘]] %%==[[Master QB1#Q00875|Q]]==%% Remember what we have learned about the [[T105 Week 1#Valence shell and valence electrons|valence shell]]. We already saw what happens when the valence shell is almost empty, that is with one valence electron. We saw that these are called conductors. We saw our examples of gold, silver, copper. If we want to bring electricity from one point to another, we would use these materials. The one you are most commonly going to see would be copper, as the others are more expensive (gold and silver). Aluminum is also a conductor, but it has three valence electrons and so it is only about 60% as conductive as the other three metals mentioned. The two most generally used conductors on aircraft are copper and aluminum. Each has characteristics that make its use advantageous under certain circumstances. Also, each has certain disadvantages. Copper has a higher conductivity, is more ductile (this means it can be drawn out into a thin wire), has relatively high tensile strength (this means it can stretch before breaking), and can be easily soldered. Copper is more expensive and heavier than aluminum. Although aluminum has only about 60 percent of the conductivity of copper, it is used extensively. Its lightness makes possible long spans, and its relatively large diameter for a given conductivity reduces corona (the discharge of electricity from the wire when it has a high potential). The discharge is greater when small diameter wire is used than when large diameter wire is used. Some bus bars are made of aluminum instead of copper where there is a greater radiating surface for the same conductance. #### Insulators %%==[[Master QB1#Q00444|Q]][[Master QB1#Q00876|Q]]==%% If we have a valence shell with almost all of its capacity met, that is, it is almost full, we see different behaviour from the electrons. They tend to work together to ensure the integrity of the atom, maintaining a stronger attraction to the nucleus, and thus are less likely to lose an electron to dislodging by an applied energy. So now we have a material that is not prone to electron flow. These are insulators. Typically Insulators have between five and eight electrons in the valence shell, and these atoms do not easily accept additional electrons, and therefore do not promote electron movement, that is, electrical current. ## Types of Electricity Electricity can be divided into two types based on their relative motion. ### Static Electricity > [!aside]- Ref >[[AMT General Handbook Ch12_1#Static Electricity|📘]] %%==[[Master QB1#Q00877|Q]][[Master QB1#Q00878|Q]][[Master QB1#Q00924|Q]]==%% Static electricity does not flow. It is essentially a potential that does not really do any work. This does not mean that it is not important, or that we don't have to understand it. It is specifically an issue in aviation, as we will see.  [[Pasted_image_20210802114408.png|➡]] In the graphic above, lines of electrostatic force leave a charged body at right angles to its surface, and then spread apart. They enter an oppositely charged body at right angles to its surface. Also notice that charged bodies reject lines of electro-static force from other bodies having the same charge. [[20210802132002.png|➡]] Like magnetic attraction and repulsion, the force of electrostatic attraction and repulsion varies as the inverse of the square of the distance between the charges. In other words, the attraction felt at twice the distance is one quarter. Conversely, the repulsion felt at one half of the distance is four times stronger. [[Pasted image 20210802185532.png|➡]] When a smooth or uniform body is electrically charged the charge distributes evenly over the whole surface. However, if the surface is rough the charge concentrates at points or areas of sharpest curvature. On an aircraft, the friction of the air on the fuselage and wings causes static electricity to build up, and this accumulation of electrical charge can cause problems. It can interfere with any radios onboard, and as you will learn, there can be several radios on board, responsible for communications, [[faculty/student/references/glossary/Navigation|navigation]], and safety features. The interference takes the form of distorting the radio waves, causing noise and inaccuracies in the radio signals required by avionics systems. The electrical charges can be a particular danger to ground crew once the aircraft has landed. The static electricity buildup will readily flow almost instantaneously to ground if given a chance. If the technician happens to be in the path between this electrical charge and the ground, the electricity will flow through the technician, with results ranging from extremely painful to fatal. You will better understand this flow and the significance of ground a little later in this course. [[Pasted image 20210803095031.png|➡]] One method to reduce the danger of static electricity buildup on an aircraft's surface is the use of static dischargers. These conductive "wicks" take advantage of the tendency for electrical charges to build up at rough or pointed areas of the aircraft to allow the built up electricity to discharge into the air, preventing larger and more dangerous accumulations. ![[Pasted image 20210806110619.png|350]][[Pasted image 20210806110619.png|➡]] ![[Pasted image 20210806110627.png|350]][[Pasted image 20210806110627.png|➡]] [[Pasted image 20210806110148.png|➡]] ### Current Electricity Electrons moving through a circuit and performing work is our main interest in studying electricity. This action generates a magnetic field, and generates heat. %% [[AMT General Handbook Ch12_1#Current|Ref]]%% When energy in the form of electrical potential causes valence electrons to leave their atom and become free electrons, this movement is referred to as electrical current, current, or current flow. These loosely bound electrons can be easily motivated to move in a given direction when an external source, such as a battery, is applied to the circuit. These electrons are attracted to the positive terminal of the battery, while the negative terminal is the source of the electrons. ## Units of Measurement ### Volts > [!aside]- Ref >[[AMT General Handbook Ch12_1#Electromotive Force Voltage|📘📘]] %%==[[Master QB1#Q00879|Q]][[Master QB1#Q00880|Q]]==%% The electromotive force that pushes electrons and causes electricity is called Voltage, and is measured in Volts (V). Voltage describes the difference in electrical charge between two points. It is perhaps not as easy to understand as current flow. You can see voltage as a buildup of electricity in one part of a circuit. This imbalance seeks to find balance, and so electrons are pushed around to even out the charge. One thing that you must be sure of, is that... - voltage does not flow. It causes current to flow. [[Figure12-37.png|➡]] Plumbing analogies can help understand this concept. In the above graphic, notice that the water levels are different. This difference in terms of electricity is voltage. As the two tanks will seek to balance each other out and cause water to flow through the pipe, so too voltage will seek to be balanced and cause current to flow. Of course, this is provided that we open the tap, or provide a path for the water to flow. To bring it back to correct electrical terms... - electrons move, when a path is available, from a point of excess electrons (higher potential energy) to a point deficient in electrons (lower potential energy). The unit of measurement of voltage is Volts, and it is abbreviated V. You will also see E used, and this stands for Electromotive Force. The actual formula to determine volts is: $\begin{align*} E &= \frac{\mathcal{E}}{Q}\\ where:\\ E &= \text{Potential difference in volts}\\ \mathcal{E} &= \text{Energy expanded or absorbed in joules (J)}\\ Q &= \text{Charge measured in coulombs} \end{align*}$ Joules is a unit of energy, coulombs is a unit of charge (number of electrons) and E represents the voltage. What you need to remember is that voltage is the potential force that moves electrons, and that it is measured in Volts (V). ### Amperes > [!aside]- Ref >[[AMT General Handbook Ch12_1#Current|📘]] Current, the flow of electrons that results from voltage being applied, is measured in Amperes, or amps and is abbreviated A. It is the measurement of the rate at which a charge flows through a conductor. One ampere is 1 coulomb of charge (which is 6.28 quintillion electrons) flowing through a conductor in one second. In formulas and on schematics current is represented by I. So, I is measured in A. ### Ohms %%==[[Master QB1#Q00881|Q]][[Master QB1#Q00882|Q]][[Master QB1#Q00883|Q]]==%% So far, we have described a force (V) and motion (I). We have not talked about what could provide friction, or restrict the flow of current. This is called resistance, and while it may seem that the reduced current might be a disadvantage, in fact, it is a natural part of electrical forces, and is required to limit currents to levels required by our circuits. In fact, a circuit with no resistance is physically a problem, in that current will simply go to the maximum, and this may cause overheating of components. Resistance in a circuit can come from several sources. Any device in a circuit that uses current will provide resistance, such as a lamp or other circuitry. If there is more resistance, there will be less current flow, and if there is less resistance, there will be more current flow. Of course there are devices whose sole purpose is to provide resistance to a circuit, and we will look into those shortly. Resistance is abbreviated R, and is measured in Ohms, named after German physicist Georg Ohm, and uses the symbol $\Omega$. 1 $\Omega$ represents the electrical resistance between two points of a conductor when a constant potential difference of one volt, applied to these points, produces in the conductor a current of one ampere. You will learn how these three elements work together very shortly when we study Ohm's Law. For now, you should make the association between the following: - V for volts or electromotive force - A for amps - $\Omega$ (Ohms) for resistance ## A Basic Circuit ### Closed Circuit %%==[[Master QB1#Q00884|Q]]==%% A basic electrical circuit requires: - A voltage source - a path for current - some resistance [[Pasted image 20210821113032.png|➡]] This simple schematic drawing shows a power source of 3V that will drive current flow through the wire and a lamp. Note that the required resistance is provided by this lamp. It is called a closed circuit, because the path for current is complete, as opposed to an... ### Open Circuit %%==[[Master QB1#Q00885|Q]]==%% Notice that the current has a full path to travel from the two sides of the battery. If this path is broken, current will not flow. This would be called an "open" circuit. [[Pasted image 20210821113408.png|➡]] [[Pasted image 20210808115953.png|➡]] Note the symbology of the battery and the lamp. In the battery symbol, note as well that the longer blade is on the positive side, and the shorter blade is on the negative. Each pair of these represent a cell, more of which later. We will see more of these types of symbols as we proceed in this course.   >So far, we have been looking at schematic diagrams. What you will see here is a representation of the training aid you will see in the lab. Each of the pieces is movable, and you can experiment with circuits. See the lines drawn on the pieces match the schematic from above. You should get comfortable with both of these ways of looking at a circuit. ### Short Circuit %%==[[Master QB1#Q00886|Q]]==%% A short circuit is one where the current path has had a shortcut put in it. This is not intentional, and it can lead to major trouble in a circuit. At the least severe, you can cut off a component from its voltage source, and thus it will not work. [[TA_SHORT.png|➡]] Worse is when you shortcut the entire circuit, and the circuit then has no resistance, and therefore no limit to the current running through it. This will cause the current to rise to maximum, limited only by the physicality of the battery and components. When the current gets to be too high for either, you will melt, burn, or destroy them. [[TA_SHORT_2.png|➡]] At low current, the circuit will likely heat up and malfunction. If the current levels are high, you will see sparks, smoke, and even flames. #### How do short circuits happen? Shorts or short circuits happen when a conductor is introduced into the circuit. If you have a screwdriver, and it is not electrically insulated, and you touch it to exposed parts of the circuit (no electrical insulation), you will cause a short circuit. Again, the risks range from heating the circuit, to a catastrophic failure of the circuit. [[TA_SHORT_5.png|➡]] If you construct a lab experiment incorrectly, you could also set up a short circuit. You will get similar unfortunate results. [[TA_SHORT_4.png|➡]] And a very important one is if you use your body to connect a current pathway from a high voltage source to ground. We will learn more about current flows shortly, but understand that in this case, your body will complete the current path. If the current is high enough, you will feel the current at the very least, and electrocute yourself at worst. [[electrocution.jpg|➡]] ## Conclusion We have seen that electricity is the flow of electrons. We learned that in order for electrons to flow, certain conditions must me met, such as an electromotive force, and a complete path for flow. We learned the units of measurement for voltage, current and resistance, and then looked at some specifics in terms of a basic electrical circuit. In the lab, you will become familiar with the protocols and training aids we will be using for this course. You will have time to do a simple experiment, and hopefully, you will see a few things that you don't understand! All will be made clear in the coming weeks. > # [[T105 Home| ◀️ ]] &nbsp;[[T105 Home| Home ]] &nbsp;[[T105 Week 2| ▶️ ]] &nbsp; &nbsp; # Lab [[T105L WS01.pdf|Lab Worksheet]] ## ![[T105L SAFETY|Safety Briefing]] ## 1. Build a Basic Circuit Your first circuit will use the elements you saw in the [[T105 Week 1#A Basic Circuit|theory class]]. We will build the circuit as given, and then we will experiment a little to see the effects of changing things in the circuit. Examine the schematic diagram here:  Using the training aids provided, construct the circuit on your circuit board so that it looks like this:  Now, let's observe a few things. Answer the questions on the [[T105L WS01#1 Build a Basic Circuit|Lab Worksheet]]. ## 2. Open Circuit Now let's see how an open circuit works:  What should you expect to see? Review the theory [[T105 Week 1#Open Circuit|here]] if you need to. Let's demonstrate this by building the following circuit:  Again, let's observe. Answer the questions on the [[T105L WS01#2 Open Circuit|Lab Worksheet]]. ## 3. Equivalent Circuits Now try experimenting with building the same circuit in different ways: ### a)  ### b)  Answer the questions on the [[T105L WS01#3 Equivalent Circuits|Lab Worksheet]]. ## 4. Making Changes We will now start making changes to our basic circuit by adding an additional battery. You will notice that there is more than one way to connect the second battery into the circuit. Try building the circuits depicted in the following circuit diagrams and take note of any differences in behaviour between the two and the circuit you constructed earlier with only one battery. If you are having trouble translating the circuit diagrams into actual circuits, consult the ➡ under each circuit diagram. ### a)  [➡](<TA_003.png>) ### b)  [➡](<TA_006.png>) As usual, answer the questions in the [[T105L WS01#4. Making Changes|Lab Worksheet]]. ## 5. More Components We will now add some lamps to this circuit to see the effect it has on the overall circuit. Build the following circuits: ### a)  [➡](<TA_003.png>) ### b)  [➡](<TA_005.png>) Answer the questions on the [[T105L WS01#5. More Components|Lab Worksheet]]. ### c)  There are two locations depicted in the pictorial of circuit 5c where you will add a wire to modify the circuit. First, add a wire at location A and take note of the changes that take place in the circuit. Remove the wire at location A and place it at location B, taking note of what happens when you do this. >Do not place wires at locations A and B at the same time! ## 6. Rearranging Circuits Now let's rearrange some components and see what happens. ### a)  [➡](<TA_006.png>) ### b)  [➡](<TA_007.png>) ### c)  ### d)  ## Conclusion Don't worry if you didn't understand how some of these circuit adjustments work. Every last detail will be explained in the coming weeks. So, stay tuned... >Clean up your bench, return the training aids, and sweep bench surfaces and floors. > # [[T105 Home| ◀️ ]] &nbsp;[[T105 Home| Home ]] &nbsp;[[T105 Week 2| ▶️ ]] &nbsp; &nbsp; [[QR T105 Week 1| 🌐 ]] &nbsp; &nbsp;[[FB T105|Please Help]]