# ATAT 105 Basic Electricity > # [[T105 Week 1| ◀️ ]] &nbsp;[[T105 Home| Home ]] &nbsp;[[T105 Week 3| ▶️ ]] &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [[QR T105 Week 2| 🌐 ]] ># [[T105 Week 2|Week 2]] >- [[T105 Week 2#Power Sources|Power Sources]] >- [[T105 Week 2#Units of Measurement|Units of Measurement]] >- [[T105 Week 2#Measurement Tools|Measurement Tools]] >- [[T105 Week 2#Meter Usage in Circuit Analysis|Meter Usage in Circuit Analysis]] ># [[T105 Week 2#Lab|Lab]] >- [[T105 Week 2#1 Voltmeter|Voltmeter]] >- [[T105 Week 2#2 Battery Check|Battery Check]] >- [[T105 Week 2#3 A Basic Circuit|A Basic Circuit]] >- [[T105 Week 2#4 Add a Battery|Add a Battery]] >- [[T105 Week 2#5 A basic circuit powered by a power supply|Power Supply]] >[!jbplus|c-blue]- Lesson Intro >### What > >In this lesson you will learn how to measure voltage around the circuit we built last week. We're also going to crank up the voltage with a power supply. > >### 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. > > >### Approach and Objectives > >By understanding the following topics, you will have achieved the learning outcome for this lesson. Consult your course outline for the learning outcomes and other details of this course. > >#### Course Learning Objectives > >- CLO 10. Assemble a functional electrical circuit using components according to a given circuit diagram. >- CLO 11. Show using a Digital Multimeter (DMM) the measurement of voltage, current and resistance in a circuit. > >### Testing > >You will be tested on this material on Assignment 2, the Midterm, and the Final Test, as per the [[T105 Intro#Testing and Grades|testing strategy]]. >[!jbplus|c-blue]- Prof >### Objectives > >This week we start to measure. We will also use the power supply. Two pieces of equipment we will use frequently in this lab. Fluency begins here. > > ### Theory >For the theory course, we look (briefly) at various power sources. This is basically just a list, and students must be familiar only. We then move into a quick review of the measurement units seen last week. We then look at how to measure them. Do not go over these too much, as they will be repeated as they come into use for the lab. >### Lab >For the lab, PPE is required, and you should refuse admittance to students who are not correctly equipped. Students should fill in the first part of the worksheet before proceeding to the activities. Answers can all be found in the SSG. Measuring voltage is the main purpose of today's lab, and the only tricky thing is to not have too high a voltage from the power supply through the bulbs and thereby burning out bulbs. Reminder that the bulbs are (mostly) rated for 6V. It would be useful to demonstrate the use of probes, as well as clip leads and banana plug leads. Students should understand that electrically, these are interchangeable, and their use depends on what you are doing in the circuit, i.e. probes for multiple measurements, leads for hand free use. ## Power Sources ### Law of Conservation of Energy %%==[[Master QB1#Q00922|Q]][[Master QB1#Q00925|Q]]==%% In [[physics]] and chemistry, the [[law of conservation]] of [[energy]] states that the total energy of an isolated system remains constant, meaning that energy cannot be created or destroyed, rather it can only be transformed or converted from one form to another. Several of the power sources found on aircraft use conversion processes to turn one type of energy into another, most notably and commonly, converting mechanical energy into electrical energy. There are many other types of power sources though. ### Types of Power Sources #### Thermal %%==[[Master QB1#Q00926|Q]][[Master QB1#Q00927|Q]]==%% There are several sources of [[thermal energy]], and some of them overlap with other sources such as chemical energy, which can manifest as thermal energy as well, especially in response to a chemical reaction. The sun is a key source of thermal energy, and is often specified as [[solar energy]]. The earth itself also stores heat in the form of geothermal energy. Fossil fuels can produce thermal energy when they are burned. Dissimilar metals can be constructed such that voltage is created when thermal energy is applied. This makes these devices suitable for measuring temperature. These devices are known as thermocouples. [[V Thermocouples|🎞]] [🔗](https://en.wikipedia.org/wiki/Thermocouple)  #### Pressure %%==[[Master QB1#Q00928|Q]][[Master QB1#Q00929|Q]]==%% Certain crystals, polymers or ceramics, when subject to mechanical stress or pressure, will release electrical power. The resultant electricity is called piezoelectricity.  #### Light %%==[[Master QB1#Q00930|Q]][[Master QB1#Q00931|Q]]==%% Photovoltaic materials can convert solar energy into electrical energy. Solar arrays that aim at the sun are used to convert energy from the sun into useful electricity.  #### Magnetism %%==[[Master QB1#Q00932|Q]]==%% Magnetism is a fairly complicated topic that we will look into a little more deeply later. The magnetic flux around a magnet can induce currents in conductors, and the machines that do this, generators and alternators and such, will be covered in much more detail later in the program.  #### Chemical %%==[[Master QB1#Q00915|Q]][[Master QB1#Q00933|Q]]==%% Some materials exist as positive or negative ions. When these materials are connected and immersed in an electrolyte an electron flow is created. A lead acid battery, or a Nickel Cadmium battery are examples of chemical processes or reactions that generate massive amounts of electrons that can be harnessed as electrical power. ![[Pasted image 20210808113047.png|350]] ### Batteries > [!aside]- Ref [[AMT General Handbook Ch12_4#Batteries|📘]] %%==[[Master QB1#Q00915|Q]]==%% A battery is a device composed of two or more cells that convert chemical energy into electrical energy. The chemical nature of battery components provides an excess of electrons at one terminal and a deficiency at the other. When the two terminals are joined by a conductor, electrons flow.  However, as the electrons flow, the chemical composition of the active material changes and, over time, the active elements become exhausted. In a primary cell, the active material cannot be restored. However, in a secondary cell, electricity from an external source can restore the active material to its original, or charged, condition.  #### Primary Cells %%==[[Master QB1#Q00940|Q]]==%% The most common battery in use today is the primary cell or dry cell. Its compact size and low weight make it ideal for use in several electrical devices that require a low power output to operate. Primary cells consume cell materials as they produce electricity. The material cannot be restored nor the cell recharged. The batteries you will see in the lab qualify as primary cells.  #### Secondary Cells %%==[[Master QB1#Q00914|Q]]==%% In secondary cells, the chemical action that releases electron flow is reversible. It is important to note that secondary cells do not produce electrical energy, but merely store it in chemical form. This is why batteries consisting of secondary cells are called storage batteries. Most commonly used batteries in aircraft are the Lead Acid and Ni-Cad type batteries. More info on these to follow in other courses. ## Units of Measurement  [[Pasted image 20210808114107.png|➡]] ### Volts As we have seen, the force that causes electrons to flow is called the electromotive force (EMF) or voltage This force is measured in units called Volts (V) The symbol used in formulas for voltage is a 'V' or 'E' ![[Pasted image 20210808113925.png|350]] ### Ohms Opposing the flow of electrons is resistance, measured in units called Ohms (Ω) 1 Ohm is the resistance through which a force of 1 volt results in 1 ampere of flow. The symbol used in formulas for resistance is 'R' ![[Pasted image 20210808114023.png|350]] ### Amperes Current is defined as the flow (or movement) of electrons The flow of electrons is measured in a unit called Amperes or Amps (A) When 6.28X10¹⁸ electrons flow past a point in 1 second that is defined as a current flow of 1 ampere The symbol used in formulas for current is 'I' The coulomb is 6.28X10¹⁸ electrons. ### Watts Power is produced when we have both EMF (voltage) and current in a circuit. It is defined as the rate at which work is being done in an electric circuit. The unit for power is the Watt (W) The symbol used in formulas for power is 'P' ### Electricity at Work ![[Pasted image 20210808114227.png|350]] [[Pasted image 20210808114227.png|➡]] This water analogy is traditionally how voltage, current & resistance have been described in introductory electrical courses. ![[Pasted image 20210808114310.png|350]] [[Pasted image 20210808114310.png|➡]] ## Measurement Tools Voltmeters, ammeters, and ohmmeters are used to analyze values in electrical circuits. Some basic rules should be followed to prevent injury to the technician or damage to the meters and circuit components. ### Voltage %%==[[Master QB1#Q00934|Q]][[Master QB1#Q00937|Q]][[Master QB1#Q00938|Q]][[Master QB1#Q00939|Q]]==%% Voltage is always measured across a component or across several components, often in reference to ground (more later on this too). In other words, the probes of the voltmeter go across, or parallel to, the component being measured. The meter is measuring the difference in potential between the two leads, or put another way, between the two points of the circuit that the leads are in contact with. If voltage was used up by a component between the leads, the meter will measure the difference, and show the precise voltage on the display screen. >If you were to touch the two leads of a voltmeter together, what would you expect to read? Well, since there is no electrical difference between 2 leads that are touching, the meter will read 0VDC. >What if you put a wire between the 2 leads? Since the wire offers no resistance, this is just the same as touching the 2 leads together. There is no difference in potential, and so the meter reads 0VDC. You will be doing this in the lab this week. Get familiar with [[T105 Week 2#1 Voltmeter|this tutorial]]. Don't worry if it's not crystal clear, it will probably be easier when you do it in real life in the lab. ![[Pasted image 20210808114706.png|350]] ### Current %%==[[Master QB1#Q00935|Q]]==%% Current is measured by placing the meter in line (series) with a component. The technician must be sure the ammeter is able to handle the current in the circuit being measured. We will learn how to do this a little later in the course. If you look at the following graphic, you will see that the meter leads interrupt the wire to the left of the [[resistor]]. This is an important distinction that we will explore in more depth later. ![[Pasted image 20210808115225.png|350]] ### Resistance %%==[[Master QB1#Q00936|Q]]==%% Resistance is measured with *power off* the circuit. Individual components must be isolated from the circuit if their resistances are to be checked. ![[Pasted image 20210808115340.png|350]] ![[Pasted image 20210808115414.png|350]] ## Meter Usage in Circuit Analysis Using meters to measure volts, amps and ohms in a circuit is how we can "look" at what's happening in the circuit. They are special instruments that allow us to examine almost anywhere in a circuit, thus learning what is happening electrically. It then becomes possible to identify where these values are not correct, and then to narrow down the possibilites until we find a defective component or wire. So, clearly the multimeter, which includes a voltmeter, an ammeter, and an ohmmeter (selectable by a switch) is a primary tool for troubleshooting. You have to be familiar enough with these tools that you can make them answer questions for you about the circuit. Improper use will either tell you nothing, or tell you wrong information. Understand that your lab time is explicitly designed for you to get your hands on these things and get used to them. Keep playing in the lab, there is always something you can try with the meters and training aids that will at least give you some practice in using these tools. Observe a few precautions though as we begin. These tools can be damaged if used incorrectly. If you don't understand these warnings, ask. For instance, we haven't really discussed polarity yet, but for now, it's the positive and negative leads, black and red. In general, we put the black on the ground side, or negative side, and the red on the positive side. Again, don't worry too much though, especially at the beginning, we will not be using voltages that will destroy the campus. That will be later. Yes, that was a joke. Please pay attention. >Observe proper polarities when connecting a meter to an operating circuit or to a power supply. >When using an analogue meter attempting to measure voltage with the meter's probes reversed drives the indicator in the wrong direction and damages the meter. (we don't have these in the lab, just FYI) ## Lab #### [[T105L WS02.pdf|Worksheet]] | [[T105L EQ W02|Equipment List]] In the lab this week, we will be expanding on some of the things we saw last week. We will build similar circuits, but this time we will actually be measuring what's going on, and slowly build up our knowledge around an electrical circuit. Your worksheet will be printed for you but you can preview it [[T105L WS02.pdf|here]] and at the beginning of this lab section. This is now the second week, and you will be denied access to the lab if you are not wearing (that means eye protection on) the [[T105L SAFETY#PPE|correct PPE]]. Go over the lab instructions before you come to campus. The more you are clear about what we are trying to do, the clearer the lesson will be, and the more time you will have to play around a bit and learn about electricity, as well as talk to your profs. Have fun... Read this safety briefing again. It hasn't changed. It still applies. This week there will be no toleration of infractions. ![[T105L SAFETY|Safety Briefing]] We will be measuring voltage this week to expand upon the basic visual observations done in Week 1. To accomplish this, you will need to become familiarized with the voltmeter function of a digital multimeter. ## 1. Voltmeter You can refer to the [[Bench DMM.pdf|User's Guide]] for full details. We will provide specific instructions for this lab here: To use the benchtop multimeter, you will need to both turn on power to the workbench and the multimeter itself:  If the main power switch is in the on position but not glowing, check that the circuit breaker to the left of it is not tripped and reset the circuit breaker as necessary or ask an instructor for assistance. Press the DCV button to put the multimeter in DC Voltmeter mode:  You will need to connect test leads or cables to the voltmeter through which it will interact with your electrical circuit. Plug the ends of your cables to the colour-coded sockets marked in the diagram below:  Depending on what is on the free end of the cables you just connected to the voltmeter, you can now either probe or directly plug the voltmeter into your circuit:   Because the whole point of a multimeter is to be a versatile yet accurate measuring instrument, it has the capability to display its measured voltage at different ranges. Ranging is normally taken care of automatically by the multimeter, but you can manually set it to operate at various different voltage ranges by pressing the up and down arrow buttons depicted below:  %% #JB maybe reference T110 for SI units (kilo, milli etc)%% You can revert back to Auto Range by first pressing the blue Shift button, followed by pressing the up arrow button. Answer the questions in the lab worksheet. ## 2. Battery Check Next, you will measure the voltage of the batteries you will be using in your circuits. An AA cell has a nominal voltage of 1.5 volts, and will progressively provide less and less voltage until it is no longer capable of pushing current through your circuit. The term "nominal" comes from the same root as "name", so the nominal value is the specified value, i.e. what the manufacturer says it is. It's the "named" voltage.  Different electrical circuits will have different power requirements, and you might notice that batteries with drastically different measured voltages will have an effect on the brightness of the lamps they are powering in the following circuits. For most uses, if the voltage of your battery dips below 1.3 VDC, it will not have enough energy left to properly supply a circuit. Connect the voltmeter as per the section above, and measure your battery's voltage. Answer the questions on the lab worksheet. ## 3. A Basic Circuit We will build the same basic circuit we built last week, but now we will measure voltage drop across different points. An important habit to develop is to identify what you expect to measure before you actually measure. In this exercise, before you make your measurement, ask yourself what you are expecting to see. The lab worksheet will remind you, and ask you to write down your expectation. ### a) Build the basic circuit you saw in Week 1:  [➡](<TA_001.png>) As before, consult the ➡ under each circuit diagram if you are having trouble translating the circuit diagrams into actual circuits. One at a time, connect the voltmeter at points A, B, and C as described in the following circuit diagram:  [➡](<TA_207.png>) Answer the questions on the lab worksheet. ### b) At the risk of demonstrating the obvious, we will also revisit the open circuit covered last week:  [➡](<TA_002_2.png>) One at a time, connect the voltmeter at points A, B, and C as described in the following circuit diagram:  [➡](<TA_208.png>) Answer the questions on the lab worksheet. ## 4. Add a Battery Next, we will add a battery to the circuit and determine the voltages depending on the placement of the additional battery cell. Again, determine first what you should be reading, answer the applicable worksheet question, and then build the following circuits and measure the voltages at the indicated points: ### a)  [➡](<TA_003.png>)  [➡](<TA_209.png>) ### b)  [➡](<TA_006.png>)  [➡](<TA_210.png>) ## 5. A basic circuit powered by a power supply Now that you have had the opportunity to familiarize yourself with both the concept and the measurement of voltage, we will now be using a power supply to further study its effects under far more precise control. ### Power Supply To use the benchtop power supply, you will need to both turn on power to the workbench and the power supply itself:  Our benchhtop power supplies are capable of simultaneously providing two power sources, or channels. In the image below, take note of the power connector sockets for Channels 1 and 2 circled in green. The output button circled in red will glow white when power is actually being output to the active channels. The channel control buttons are circled in blue, and light up to provide the following indications: - Channel button unlit: Channel OFF - Channel button glowing green: Channel ON - Channel button glowing blue: Changes in settings are being applied to this channel  The following image highlights the controls used for making adjustments to output parameters. The voltage button circled in red will glow white when the power supply is in voltage set mode; the channel where adjustments will be applied will also glow blue, and the arrow buttons circled in blue will also glow white.  While in voltage set mode, turning the adjustment knob shown circled in blue will adjust the voltage of your chosen power channel. The left and right arrow buttons can also be used to change the magnitude at which you make the adjustments, which is indicated by the highlighted digit on the LCD display:  It is best practice to have the output of the power supply switched off while making any changes to the output settings. ### a) You will now build a basic circuit to apply power to using the benchtop power supply, and get comfortable with making adjustments to the amount of voltage it outputs. Build the following circuit:  Feel free to experiment with different supply voltage settings and measuring different points of the circuit with the voltmeter. Follow the prompts on the lab worksheet. ### b) Now we will add some extra bulbs into the mix and measure how they interact with different voltage settings:  Follow the lab worksheet and answer all questions. >Clean up your bench, return the training aids, and sweep bench surfaces and floors. > # [[T105 Week 1| ◀️ ]] &nbsp;[[T105 Home| Home ]] &nbsp;[[T105 Week 3| ▶️ ]] &nbsp; &nbsp; [[QR T105 Week 2| 🌐 ]] %%&nbsp; &nbsp;[[FB T105|Please Help]]%%