go ahead and get started so welcome to eggn 281 that's the introduction electrical circuits just want to make sure everybody's where they think they're supposed to be so that that's what this course will will be covering what I'd like to do here initially is go through some of the aspects of the the syllabus with you just to point out the administrative aspects and how you'll be evaluated that type of thing okay this semester there are six sections of this course I'll be teaching two of those sections and then the other professors Dr dve Dr smoes and Dr Ahmed so it's nice from the perspective the the class sizes are a little smaller this time so I I'm hopeful that that will encourage interaction so please feel free to to ask questions if there's something that's unclear happy to to stop and try to elaborate on particular points you'll notice all the instructor contact information is provided and I'll just point out I'm much more likely to respond in a timely fashion if you email me I have a bad habit I ignore my phone phone message box so you're welcome to leave that but I think you'll get a better response if you email me all right the prct for this course is physics 2 so if the registr is doing their job you weren't able to enroll without completing physics 2 I'll talk a little bit more about that course in a little bit the course objectives and the course description are provided I would encourage you to look at that probably the objectives that is most worthwhile at the end of the semester to see if you believe that we really accomplished the objectives that we set forth okay the Blackboard we will be using that to disseminate information so I I do want to emphasize it's important that you check that on a regular basis homework solutions review material for exams old exams that type of thing will all be posted on blackboard as well as your grades will be posted there so that gives you a way of making sure that we've recorded the correct scores for the various homework and and exams all right comments on the textbook do want to emphasize that you are likely to see two versions so I just want to explain this is the the full version of the electrical circuits text it is is 18 chapters worth um we will only cover the first nine and so most of you will probably find the the custom text more a little more economical approach in other words it just essentially gives the the nine chapters that we will actually cover I do want to emphasize if you are an electrical major you might consider getting the the full text because the follow-up course Circ two will then cover the remaining nine chapters so that that's an option the other thing I want to stress is when you purchase this text uh you will or you will need an access code to mastering engineering we intend to use that platform for online homework assignments so you will need to purchase that access code I it's my belief most of you probably have gone through Statics so you are familiar with the mastering engine ing platform so that shouldn't be too new of a a process just a continuation with with that type of platform all right the homework I want to emphasize that each homework assignment will consist of two parts there will be an online portion so in fact if you have signed on to mastering engineering that first assignment became active at 8 a.m. this morning there are two parts to that just a brief introduction just emphasize some of the logistics or administrative aspects of mastering engineering and then the first circuits assignment and then also we will be assigning typically four to five written problems each week it's very important particularly as you prepare for the exams that you get familiar with uh the the process of laying out circuit analysis in a very systematic fashion so I I don't think if we just essentially assign only online assignments that you get uh practice in that type of thing that will help you prepare for the the exams I'll talk a little bit more about uh the course outline here momentarily but I do want to emphasize that homework assignments are always due on Wednesday the written assignment please get in the habit when you come into class just put those at probably right on the the desk up by the podium and then the online assignment is due 5:00 p.m that same day so always homework is going to be due on on Wednesday that being said the first assignment is then due a week from Wednesday so that's January 16th okay um it mentions short quizzes the possibility of that have to be honest in here there is so much material to cover that last semester I only gave one quiz I imagine that's pretty representative of what will happen this semester as well so I will announce quizzes in advance so it's something that I deem to be extremely important if I dedicate class time to to quizzes so I I will let you know in advance all right more comments on the syllabus about mastering engineering so I'll just call your attention to what you need to do to register for this class and then the third page talks about how your grade is established so you'll notice both uh the online homework and the written homework are worth 10% we have instructor discretion and short quizzes for 5% and then this semester we have two exams during during the semester and a final so each one of those exams is worth 25% so as you imagine a lot writing on on those exams so very important uh to make sure and prepare for those we will be using the the plus and minus grading scheme in here so the the grade allocation is is laid out in that in that table one thing I want to mention um there's a heading titled attendance so I want to give you my perspective here now in a smaller class I will certainly miss you if you're gone I'm not going to take attendance but here's here's my point electrical engineering is an extremely abstract subject you're going to to need my help I believe to really Master the material reading the the textbook will certainly be important but I I think it it's very important to make attendance a priority I've had people mention to me if they miss a class they have no idea what I'm talking about this class moves at a very high rate of speed so you would be surprised how much material you may miss if you are are gone for a lecture again that's my my plea is I will promise not to waste your time in here I know you're all very skilled readers I don't plan to regurgitate or review what in the textbook my intent is to supplement the material to give you other perspectives that help come to grips with trying to visualize the invisible which is what we're asking you to do largely in the realm of electrical engineering G the attendance policy or not the attendance but the academic dishonesty policy is just published here that's a request the administration asks us essentially to here to I do want to to emphasize one of my concerns is I'm very well aware that solution manuals are readily available to this material uh that being said you know if you just go through the process of copying down a solution that does you absolutely no good and my my graders are are pretty astute at recognizing that so just be aware that the possibility exists that might ask you to explain that material to me if I just see the the material directly copied from a solution so again homework is that to help you master the material just copying it blindly does you absolutely no good whatsoever all right so with with that I do want to mention on the remaining three pages the semester is laid out day by day so today we will be beyond the introduction of the material we'll look at some fundamental circuit principles the the reading you know unfortunately you're already behind ideally you would have read the the first 18 pages of the text if you can read the material in advance of the the lecture I think it just it helps um solidify that material and then you'll notice on the 16th of January the the homework assignment that's when that is due so there is once again the online component and then the the written component and then um know beyond that the exams are described we are giving exams since there are six sections we'll give those during the common exam time frame so those are are laid out as as describ so with that are there any questions about uh the syllabus the administrative aspects of of the course all right did everybody get a copy of the syllabus so as we begin this process together I think there are two questions we should probably consider so the the first question and I'll I'll try to clarify this because this may strike you as a bit odd but the first question I think we should consider is why are you taking this course now the reason I'm asking that question is as I look through the the class list I noticed that less than 10% of you in here are declaring electrical engineering as your specialty and so what I interpret that to mean is some point in your life you decided that to do something other than follow electrical engineering as your your dream job or whatever that might be when you were really young you stuck a butter knife in a wall outlet or a set of keys this spray of Sparks if that didn't terrify you enough the adults yelling at you certainly did maybe it was later in life physics 2 so that could be fairly recently you decided that no way do you want to do anything electrical if physics 2 is a repres presentation so the point is for some reason the majority of you in here are non-electrical engineering Majors so let me return to my question why are you taking this course then exactly that's the the answer I would expect it is required in other words your faculty or the faculty that essentially administer your degree requirements are stating that to get an undergraduate degree from the Colorado School of Minds you must endure eggn 281 inro circuits now here's the important point it's your faculty under which you're getting the degree that sets your degree requirements not me so if you are frustrated by having to sit here um I can't help you you would have to address those problems to the The Faculty that that you're directly getting the degree from so here's another point I am truly here to help you I an ally in this process and I I hope you come to to believe that as the semester goes by I can help you get through this this course and hopefully in the end you will see why it's so important to have a basic understanding of electrical engineering I certainly agree with your faculty that you need that we live in an electrified World certainly as an engineer you have have to have some basic understanding of electrical phenomenon so again I I certainly support that non-electrical students are required to take this class um some other aspects where this course may become very useful how many of you know of and plan to take the Fe exam okay so good um hopefully by the end of the semester you'll all raise your hand when I ask that same question the Fe exam is the fundamental of engineering exam it's the first step in becoming a professional registered engineer and for a lot of you that will certainly be a requirement to meet your professional goals another aspect I can guarantee that you'll be working on multi-disciplinary teams where you will likely be working with electrial engineering Specialists it's important to be able to at least have some idea what they're talking about and and guide that process a lot of reasons you're here so that's why you're taking the course other than it's just a requirement for graduation that being said the second question if the faculty under which you study have decided that you need to take this course it's probably important to ask yourself what is electrical engineering so anybody want to take a an attempt or stab at that particular question incidentally as you probably know electrical engineering is a huge vast field of study so it it's a little challenging that break that down into a nice concise definition so here's what I would would generally tell people if you're trying to to grasp what electro engineering involves if it involves processing energy or information it is likely going to fall under the classification of electrical engineering so I will refer to that definition frequently throughout the semester might as well get that well ingrained right now so I could spend uh the remaining class period just talking about energy and information but I don't think that's really what we want to do let me just briefly mention some things that you should be well aware of that fall under those those two headings so in other words what I would ask on a day-to-day basis think about how much you depend on electrical phenomenon or electrical engineers to do their job so that things that you take for granted are are working properly so what's a good example under energy okay um yeah I I'll mention computers um under the information cuz processing you know using ones and zero binary so definitely you're all aware how much we depend on computers from an energy perspective we distribute we generate and we utilize power electrical energy so that that's one thing looking there so in terms of power another aspect under energy would be electromagnetics so the use of electrical and magnetic fields and incidentally I think it's important for you to to know the perspective your instructor brings so that the area that I work most closely with is the the power aspect that doesn't mean that I'm unable to to Really address the other aspects but certainly that's my my area of expertise and then under information you mentioned computers so definitely excellent example what are other examples of information processing think of all the communication tools we rely on so so cell phones radios television there are certainly many examples in all the engineering disciplines that you represent here in this class of control systems in other words automated Control Systems is is common in all the engineering disciplines so Control Systems signal processing so that just gives you a sampling of of some of the things we're describing some of the areas that are essentially under the the context or the heading of electrical engineering all right another thing to mention it's reported that the i e which some of you will recognize that's the Institute of electrical and electronic Engineers it's the electrical engineering professional Society it's reported to be the largest engineering Society in the world indicating just what a a vast field of study this has become um another question how many of you are involved in the professional engineering society that essentially represents your degree that would be another thing by the end of the semester I hope all of you raised the your hand that is such an excellent way to network to make contacts to to get timely information about your field of study they generally give you really good discounts as a student so I'd encourage you to to consider joining one of your or whatever professional Society is representing your degree all right so little bit of discussion about the course this course as the title indicates is an introduction to circuits that means we have to spend the majority of time on circuit analysis and problem solving the reason that's how we're going to focus our time is Once you master the foundation of circuit analysis and problem solving you have the foundation for any other aspect of electrical engineering that you might need to to study this course moves at a high rate of speed I can't overemphasize that we have a lot of material that cover so it's very important that you don't fall behind if I see students struggling it's usually because they don't get that good foundation from the beginning if you really focus on learning the circuit analysis techniques what comes later in the semester should fall into place nicely so I encourage you get help make sure that you get up to speed with the techniques we'll start with all right so any any questions on on that so what I'd like to spend the remaining part of the day doing is just give a A Brief Review of the electric circuit fundamentals okay so if you go back to physics 2 what hopefully you glean from that course is that electrical effects are attributed to separation of charge and charge and motion so separation of charge you should recognize as voltage charge and motion recognized as current so again all electrical effects are attributed to charge being separated or the movement of charge so that's where we want to start is just quickly looking at the following fundamental quantities charge voltage current and then power and energy I just want to make sure as we get started that everybody's on the the same page that we essentially have the the same understanding same perspective so just a couple quick things to review charge on electron given as 1.62 * 109th charge is measured in in koloms and then charge on a a proton okay one thing I'll I'll reference is the the bipolar nature of charge that's significant and that gives a lot of initial problems with sign conventions so as your instructor anticipating where you might have problems I I'll try to focus on really getting a a system in place where you don't have to worry about the signs and the directions and that way you don't have to be concerned about that and you'll let the circuit analysis take care of itself so to speak okay next current we mentioned that's the the movement of charge so current is described as the time rate of change of charge so it gives us a good opportunity to just quickly review units of of current cool per second and you hopefully recognize that by a more common representation and what would that be yep an amp here or amp for short all right so this this may seem like u a funny thing to to focus on but again recognizing some of the problems that that people find pertaining to Circuit analysis I I really want to emphasize the following charge is bipolar that means if we're going to designate a current to correctly and completely describe it we have to indicate a magnitude and a Direction in other words you can't give one without the other to fully and completely define that that current so let me just show you couple of equally valid ways to present information about a current flowing in a particular segment of a circuit all right you might choose to indicate the the direction of current from left to right and indicate that its magnitude is 10 amps and it's equally correct to designate that same current flowing from right to left as a -10 amps so that that may seem like I'm stating the obvious but I'll I'll come back to the significance of that as we get further into the circuit analysis next fundamental quantity voltage so I just want to emphasize here separation of charge so it's the amount of work done per unit charge in separating so we can designate that as wdq so here again good opportunity to review units so Jewels per kulum or more commonly called a volt now you're going to notice there's a familiar theme here because charge is bipolar that means that to correctly designate and specify a voltage we have to show a polarity and a magnitude so if I take a circuit element and want to present or represent a voltage of C assciated with the circuit element couple of equally valid ways I can do that I might indicate the polarity this is the higher polarity side voltage is 50 volts or if you prefer change the polarity and then designate that as a negative 50 volts again equally valid either way now for whatever reason I'm convinced that that students look at a negative sign and assume they've done something wrong and that's something I've got to break you of if if that's the kind of the belief you have at this point then the the final two electrical quantities power and energy so power is the the rate of energy transfer and if you notice in the context of what we've just defined when we're talking about power associated with an electrical element it is the voltage across that element times the the current flowing through that element so in the future anytime I ask the question what's the the power associated with an element all you need to do is multiply B and I together again I'm assuming this is all review that units juwel per second or more commonly called a watt so I imagine you anticipated this was coming if we have to worry about Direction and magnitude for current polarity and magnitude for voltage we're going to have to adopt some kind of sign convention for power the one the textbook uses and the one I'll use as well is What's called the passive sign convention now initially this may seem a little bit clumsy to you but but trust me once you get proficient you'll understand why we put so much emphasis on this the sign convention all right a question for you from a power perspective and from a circuit perspective what two types of elements are there again from a power perspective if you were going to classify in a circuit what are the two types of of elements you would see okay so resistive is an example like lighting is is resistive so it's a a load it's something that is taking energy from the system so we yeah that that's certainly a good example of one category that would be a load what would be the second absolutely so a source is the the second type you have to have generators or or something in the system that are actually producing that electrical energy so we're going to take that perspective as we described this convention so a passive element is what we recognize as a load on the system now here's the the criteria that you need to be watching for as it pertains to a passive element passive element the current is going to be flowing into the positive terminal as it pertains to the the voltage with the passive sign convention we then calculate the power as B * I as we described and then just want to emphasize the interpretation the power dissipated so the power dissipated by a passive element is positive that's the the first half of the sign convention okay so sources are described as active elements and what you'll observe is for an active element the the current now instead of entering the positive terminal it leaves the positive terminal and we will compute power as negative B * I for and then some wording to go along with that the power dissipated by an active element is a negative quantity yes sir yeah and that's uh excellent question for everybody to ponder so that the question what is meant by in the latter case power dissipated by an active element is a negative quantity what's that another way of saying absolutely and it may seem clumsy at at first glance but as we develop these systematic methods of circuit analysis if you if you give it time you'll see why that's such an advantage to have that yeah this is simply saying that a active element is providing energy to the system but we will use or rely heavily on this passive sign convention any other questions on that and the time remaining just want to briefly address some terminology and again you'll you'll see as the semester evolves why having an understanding about some terminology that we'll discuss is going to be so important so let me just start by defining a circuit a circuit is simply an interconnection of circuit elements so let's just take a hypothetical case and then certainly something you determine or utilized in your physics 2 experience for the time being how are we going to treat the wires that we use to interconnect the circuit elements other words should we worry about some incremental resistance those wires have no for starting we will treat the the wires as perfect conductors and we won't worry about that now on the other hand if you're looking at a power system where we've got 100 mile transmission link you think you can ignore the resistance there no so you always have to change your model based on the situation but but certainly as we start this process we won't have to worry about the wires so here's a simple circuit a little later on in the course we're going to develop What's called the node voltage method it's by far the most powerful circuit analysis technique that we'll ever present so you better know what a node is otherwise you're going to be right off the start having trouble with the node method so a node is described as a point where two or more elements join I'll wait till a little bit later but the textbook does make that distinction between what's called an essential node and a non-essential node but for now a node is just the point where two or more elements join how many nodes are in my example okay so two everybody agree with that all right so let's identify the nodes so that's certainly a node there there's a node there and then these are easy to miss that's also based on our definition of node so there are three nodes in in this example everybody clear on why those three points represent the nodes in the circuit all right next let's discuss a loop I imagine from physics 2 most of you have a little more experience with with the concept of a loop and maybe you do with a node so a loop is simply any closed path in the circuit so how many Loops do you see in this circuit yep so three is correct so we've got Loop there Loop there so again any closed path as long as you where you start you return to that designates a loop and then finally the the other topic I'd like to mention is the concept of a mesh we will also develop what's called mesh current analysis an equally powerful circuit analysis technique so it's important that you recognize how to identify meshes I guess there's really no clean way to describe this so for lack of a a better definition I would describe a mesh as a loop not containing other Loops another perspective you could view that as panes of glass and a window of the various panes would represent where the the meshes are are going to be flowing so in this example how many meshes are there yeah just two as you may recall from Kirk off's laws that you certainly spent a lot of time on in in physics 2 if we're dealing with Kirk off's current law our focus is going to be on nodes if we're dealing with Kirk's voltage law our focus is on Loops in the circuit okay so KCl Kirk's current law is really nothing more than the statement of the conservation at charge a nice clean way to summarize KCl is is to indicate if you sum the currents at any node the the net current entering a node must equal zero so again conservation of charge Second Law then kvl or kirkoff voltage law that is a statement of the conservation of energy so a nice way to to represent that is to essentially pick any Loop any closed path in the circuit and simply state that the algebraic sum of the voltages around any closed path must equal zero now you can this may seem like I'm overstating things but essentially everything we do in this class from this point on is going to be based on those two laws so I I just want to get you thinking in advance if you see anything that violates those two fundamental cornerstones of physics then you should become suspicious that that even though it's drawn on a page in a textbook or up on the board probably can't exist or definitely can't exist and that that's going to help you understand when they begin to ask you is this a valid interconnection what the perspective will be so this is a good place to to stop for today any any questions before we conclude all right see you on Friday