Finally, that you are able to see me and hear me, this course is entitled basic electrical circuits, welcome to the course I am Mahgen Rakhishanapura from the department of electrical engineering at IIT Madras. What we will do in this course is to learn about ways of analyzing circuits, ok. So, it is not about any particular circuit or any particular gadget, but a general technique for analyzing any circuits which you can expand to any new circuit that you may come across, ok. As I mentioned earlier, please feel free to interrupt the lecture by raising your hand and I will also try to be systematic and give you time, let us say every few minutes every 10 minutes or so, so that we can have fuller doubts here, ok. Here is a presentation that sort of outlines what we will be seeing in this course, ok. In fact, it turns out that in this semester, I am also teaching a course at IIT Madras entitled Electrical and Magnetic Circuits. What I will be talking about in this online course will be only the electrical circuits part of it, ok. Now, what are electrical circuits? Electrical circuits are interconnections of electrical components and basically they every electronic or electrical gadget that you see forms an electrical circuit, ok. And magnetic circuits just as a point of information are interconnections of magnetic components and I think all of you would be familiar with transformers and motors, they form magnetic circuits. In this online course, our focus will be on electrical circuits and they are absolutely everywhere around us, you will be able to see electrical circuits we are probably using so many electrical circuits in your day to day life, ok. So, just as an example, the laptop on which I am making this presentation, your mobile phone, music player, the headphones that I am wearing, all of these things form electrical circuits, ok. In this picture, you can see an example of mobile phone which is opened up and it has a number of complicated circuits inside. You build up the circuits hierarchically from simple elements to more complex circuits and they are put together to make a bigger circuit and so on. So, finally, you end up with a very large circuit, ok. As I was saying, a mobile phone is a circuit as you see a music player and so on. And here I have shown a very large, physically very large circuit on the left side. It is a transformer that is used to bring power to your homes and that is also a transformer. And on the right side is another transformer. The one on the left side is probably has a bigger, even bigger than this room in which I am sitting. And one on the right side is a couple of millimeters, they are both transformers, ok. The main point I want to drive home is that circuits themselves come in all shapes and sizes, but there are some methods of analysis that are applicable to all circuits and that is what we will be discussing in this course. So, as I said, this course is about analysis techniques applicable to all circuits and it is not about any particular circuit and it turns out that if you look at electrical engineering curriculum in any university, this turns out to be one of the most important courses, ok. Mainly because it lays a foundation for a number of courses that you will encounter in your electrical engineering curriculum such as networks and systems where you will analyze circuits using more advanced techniques such as Laplace transforms. And some of you may want to do courses in analog circuits. The things that you learn in this course, the methods of circuit analysis are absolutely essential for that course. And also some of you may be studying in detail electrical machines. Again the analysis methods learned in this course will be useful for that. And it turns out that also if you want to get a job in electrical engineering and a lot of electrical engineering companies the interviews will start with some basic electrical circuit questions, ok. So, it is by and large a very useful course for your further studies as well as your career and so on, ok. Now, what are the topics that we will go through? First we will have a discussion on electrical quantities and elements. Some of you would be already familiar with this, ok. I think all of you will have some notion of what a voltage is, what a current is, what a resistor is and so on. And also you would have studied both in high school and later some basics of electrostatics and electromagnetics, ok. And the things that we deal with voltages and currents are related to what we study in electromagnetics such as fields and charges, ok. But we will not deal with, we will not go down to the level of fields and charges but we will stay with voltages and currents. So, in the initial part of this course I will also tell you how these things are related to each other, ok. Then after we discuss electrical quantities and elements we will see how to analyze circuits. Again at some level for very simple circuits you would be familiar with this. But we will see how to scale it up for large circuits which could be arbitrarily large, ok. Now it turns out that there are also certain theorems, certain general theorems about circuits which are very useful in analyzing circuits in representing circuits and so on. We will discuss those things. Then we will talk about what are known as 1 and 2 port networks. It will be very clear what I mean later, ok. One port means you have one set of terminals where you can apply voltage or apply current. Two ports means there are two such ways of terminals where you can do the same and so on, ok. And there are ways of transforming between multiple ways of representing these circuits we will also study those things, ok. Now one of the other interesting things that we will study is the op amp not in great detail but as an ideal op amp it forms a basic network element. And from that you can make a number of interesting circuits. In fact some of you who may have had building circuits as a hobby would have already done this, would have already used op amps. What we will do in this course is to lay a proper foundation for that and then if you want to design new op amp circuits how to go about doing that and how to analyze complicated op amp circuits those things we will deal with, ok. Now it turns out that essentially circuit analysis consists of you look at the circuit based on the circuit you come up with the number of equations and then you solve the equations, ok. Now if your circuit has only resistors then you will end up with a set of algebraic equations and you have to solve that I think you already know how to do that. It turns out that you can also make interesting circuits when you have capacitors and inductors. In those cases you will end up with what are known as differential equations and some of you may know how to solve it. What we will do is go through the treatment of differential equations the particular kind of differential equations that is constant coefficient linear differential equations that we will use in this course we will deal with that in some detail so that you are familiar with the kind of solutions that can be present, ok. Now finally we will look at polyphase circuits at least some of you would be familiar with 3 phase power transmission and so on. So we will look at some of those things and see why those things are important and see how to analyze those circuits, ok. Now in those online version of the course we will not be dealing with magnetic circuits but you can look at other resources to get some knowledge about those things, ok. Now as far as the goals of this course are concerned it is very simple you learn circuit analysis and learn how to do it well, ok. And the way to do it well is to practice, practice and practice problem solving. Now you practice problem solving for many different reasons sometimes you do it for competitive exams where you solve the same kind of problem many times so the next time the same type of problem comes up you do not have to think about it. Now here it is a little different, ok. The reason for practicing solving a lot of problems is to be confident enough of solving any other problem it may be of the same type, it may be of a slightly modified type or even a completely different type, ok. Any problem that you have to solve you have to be able to approach it with confidence and then solve it. So that is why you have to solve the number of different types of problems, ok. And also more importantly when you solve any problem you have to understand every step of problem solving, ok. It is not a test of speed but you have to know why you are doing what you are doing. So whenever you solve any problem please make it a habit to understand every step and then move on to the next step, ok. And the sort of secondary goal is to learn about linearity. What I mean by this will become clear but a large number of circuits that we will analyze will turn out to be linear. What it means is that you apply certain stimulus you will get some response, you apply another stimulus you will get a different response and you combine the two stimuli the response turns out to be the combination of the original responses, ok. Now this simplifies analysis of grade D it turns out that you do not have to analyze the same circuit many times. You analyze it for one set of inputs you will know the answer for many other types of inputs, ok. In fact any other set of inputs. So you have to become comfortable with this the implications of linearity how to recognize linearity and exploit it while analyzing circuits, ok. Now here are some resources that you can use first of all as I think was already mentioned to you these lectures these online sessions will be recorded and they will be made available to you. In addition to that you can make note of a URL that I will give you. In our group we record our lectures and you can view those lectures and one of the courses that we have taught is this electrical and magnetic circuits which are some overlap with the course that I am teaching now but is at a quicker pace. So you can view those lectures. You of course are familiar with NPTEL I think that is how you came to this course so NPTEL lectures are also very useful on specific topics. And the VLSI group home for IIT Madras this is also something that you can use to further your knowledge of circuits, ok. So with that background perhaps we can get started. I am going to share the journal now, ok. I mentioned some resources. I am going to write down the URLs here. This has recorded lectures on various circuits related courses and we can also see, ok.  So with that background we can get started with our course. Electrical circuits are interconnections of electrical components and they manipulate voltages and currents in some weight, ok. Now I think all of you have heard of voltages and currents. I would like some responses from the participants. What is the voltage? Perhaps we can type it into the chat window. Ok, I have got a number of responses here. I have got a number of responses and basically they kind of fall into two classes. You say that either the voltage is a potential difference or it is related to some force that causes current or that causes electrons to flow, ok. Now both of these are of course quite correct and I will elaborate on these things. And similarly I would like some responses on what is the current? What is an electrical current? Ok, again I have got a number of responses which say that a current is basically flow of charges, ok. And some of you say electrons which is quite correct of course, ok. And some of you also said that it is the rate of change of charges or rate of flow of charges and these things are quite correct, ok. And in the definition for the voltage some of you also related it to the electric field which is quite correct as well, ok. Now I think all of you know that all of you have at least heard of Maxwell's equations. So it relates electric fields and magnetic fields and charges, ok. So you have charges that can create electric fields and charges can move under the influence of electric field they can move under the influence of a magnetic field and so on, ok.  If you also recall from electromagnetics usually it is quite difficult to solve the problems usually you end up having to do a lot of mathematics. But in circuit things are a lot simpler the reason I will explain shortly, ok. We are also dealing with electric fields and magnetic fields and flow of charges under the influence of either the electric field or the magnetic field. But there are some conditions that make our life a lot simpler we can do things lot more easily. And our primary variables will be voltages and currents and these will be related to the fields, ok. But what we usually deal with are not the electric field or the magnetic field but voltages and currents, ok. Now first let me take an electric current and electric current usually denoted by I is the rate of flow of charge across some surface, ok. So you could have some surface I am showing some pipe like thing and you could have charges flowing this way and the rate of change of charge across the surface is the electric current through the surface, ok. Alright couple of things I think all of you know that it is electrons that do the flowing it is the electrons that flow and electrons are negative charge. So what we are looking at what is defined as the electric current is the flow of positive charges, ok. It is really the negative of the flow of electrons. Now as far as we are concerned it is perfectly alright to think of positive charges are flowing although it is electrons that are flowing and the direction of flow of positive charges will be exactly opposite to the direction of flow of electrons which are really the things that are flowing, ok. It is ok for our purposes to think of currents as rate of flow of positive charges through some surface, ok. And also generally a very useful analogy for electric current is fluid flow, ok. So instead of charges that are flowing you can think of fluids that are flowing in pipes and so on and for a number of cases which involve general rules about currents this fluid flow analogy works quite well, ok. Now in our particular case we will not be looking at charges flowing in arbitrary surfaces we will be looking at currents that are confined to a wire and a wire is a very good conductor in fact we will think of them as ideal conductors which offer no resistance at all to the flow of current. So we will be looking at currents that are confined to wires. Now this is one of the aspects that make our analysis quite simple, ok. If you have charges in fields somewhere it is not very easy to calculate the effect of fields on charges exactly how they move and so on but we will be looking only at electric currents in a wire or through some elements. So our job is a lot simpler, ok. So you may have some wire like that and you could have a current flowing from A to B, ok. Now as I said many times this really consists of electrons flowing from B to A but we can think of it as positive charges flowing from A to B, ok if the current is in this direction, ok. And we also do not worry about exactly how the charges are distributed across the surface of the wire we will be only concerned with the total current flowing through the wire, ok. And I think many of you know this already the electric current has units of ampere, ok and this corresponds to carrying a charge of one coulomb in one second, ok. So if one coulomb of positive charge flows from A to B in one second that constitutes a current of one ampere from A to B, ok. So here I have shown a wire from A to B and I draw an arrow from A towards B and I mark one ampere and that is what this means, ok. One coulomb of positive charge flowing this way. Now I could also show the exact same situation What is the chat deletion you think it is good about that? Yeah, but I did not get anything exposed here. Over here on full screen, ok. No, I mean I was saying other things. Yeah, it is ok, ok. So I believe things were interrupted for a little while what I was saying was that a current of one ampere means that a charge of one coulomb is carried over the duration of I mean a charge of one coulomb is carried in one second, ok. Now when I have a wire from A to B as I have shown here, ok and mark an arrow from A towards B and write one ampere that means that a positive charge of one coulomb has gone from A to B in one second, ok. Now the exact same situation can be depicted by having a wire with an arrow drawn from B towards A and with minus one ampere marked on it, ok. Now this is something that you have to get comfortable with you can depict the current, the same current as positive one ampere going from this side to that side or negative one ampere going from that side to this side. The reason this is important, this looks rather trivial the reason this is important is that when you solve for circuits when you start solving circuit you do not know which way the currents are, ok. You have to assign some variables I and mark the directions of currents and I could come out either positive or negative and in later cases we will see that it could even be time varying, ok. Now for you to interpret these results correctly you should become very familiar with the convention, ok. What I want to emphasize is that just because I have drawn an arrow from B to A does not mean that current is actually flowing in that direction it could be the negative applied also, ok. Value could be come out either, value could come out either positive or negative, ok. So that is about currents. So any questions, anything that is confusing about the definition of currents and the convention of the sign we will be talking about currents through wires, ok. Ok, there were a few questions. First one was what is a coulomb, ok. Coulomb is the unit of charge, ok. You perhaps know that electron has a charge of minus 1.6 times 10 to the minus 19 coulombs, ok. So roughly speaking you need 10 billion billion electrons to be flowing to have 1 ampere of current in 1 second, ok. You should have 10 billion billion electrons flowing in 1 second to have 1 ampere of current. So that is the unit of charge. Now there was another question which was about the current flows only on the surface of the conductor or not. Now we will not worry about that, ok. Now it turns out that at low frequencies current flows uniformly through the surface of the wire and as you go to higher frequencies it tends to go towards the surface uniformly through the cross section of the wire at low frequencies. And as you go to higher frequencies it will be only towards the surface of the wire. But for us those leaders are not important at all we will be looking at the total current flowing through the wire, ok. And there was another question on the flow of current through coils. Now whether it is a coil or not current will flow through the wire, ok. As you are probably asking about what happens due to that current there will be magnetic fields but we will not be talking about it at this juncture, ok. And someone else asked whether any random movement of electrons becomes a current, yes it does, ok. In fact electrons are moving randomly all the time and there is a big field of study on noise which is the electric current due to random movement of electrons, ok. As long as the temperature is above absolute 0 this will keep happening. Now there was another question on the positive charge why we take it that way. So this is something historical. I think historically people did experiments with electric currents on all kinds of things when it was not known that electrons are the, electrons are what? Carry current, ok. So they just decided the direction of current as the direction of flow of positive charges and it should also be noted that in certain chemical experiments it could be some positively charged ions that are actually flowing, ok. When we have wires it is only negatively charged electrons that are flowing but that is not the case in every situation. So it is some arbitrary thing and that is the historical convention and we will stick to that, ok. There are also questions on AC and DC and so on. So those things we will not worry about, ok. That is just has to do with how the current changes over time, ok. So that is not something fundamental and so that is about those things. And also for us all conductors are perfect, ok. So the conductor itself will not have any influence on the current, ok. So this is an idealization and many of the wires that we use which are made of copper come fairly close to this ideal level, ok. So again we will not worry about the effect of wires at this point, ok. Now let us now let us move on to the other electrical quantity which is the voltage or potential difference, ok. Now what is this? I think again an analogy could be made with gravitational field, ok. You know that if you have gravitational field, this is the, I am showing only a small area so I am showing it as flat and you know that there is gravitational field in this direction, ok. Now if I place a mass M in a gravitational field what will it do? Obviously it will fall in some way towards the earth, ok. In fact the gravitational field could be due to any body and it will always fall from a higher gravitational potential to a lower gravitational potential and let us say this was at a height h2 above earth and the other one was at a height h1 above earth. When it falls from h1 to h2 it gains a potential energy which is mg times h1 minus h2, ok. So it falls from a higher potential to a lower potential and while doing so it gains potential energy, ok. Now similarly if you have an electric field which is usually denoted by that and then you place a charge q it will, this is of course a positive charge q it will fall. I mean here I use the word fall not in the gravitational field but in the electrical field, ok. So it will go from there to there, ok. It will tend to go and if it does that it will also gain a potential energy which is q times let us say the potential this electric potential is denoted by v and if this is v1 v2 it will be v1 minus v2, ok. You see that the gravitational potential energy that is gained is proportional to the mass, ok and the electrical potential energy that is gained will be proportional to the charge. So we leave out this if this charge and mass are property of the body that is falling and the rest of it is the property of the field, ok and that is the potential difference, ok. So the amount of energy gained is equal to the amount of charge times the potential difference between here and there and that is v1 minus v2, ok. Similarly here in the gravitational case the amount of potential energy gained is the mass of the body that is falling times the potential here minus the potential there which is g times h1 minus h2. So what I want to emphasize here is that the potential makes sense only when measured as a difference of values between two points, ok. It is v1 minus v2. If you just say potential at this point is something that is not a very significant thing, ok. So you always have to measure this voltage or potential difference between two points and this is true of circuits as well, ok. Now as usual we are not looking at arbitrary fields that are distributed in space and charges falling in this. They are only looking at electrons moving in wires or charges moving in wires and the fields will be inside the wires, ok. So the potential difference the electrical potential difference is very much like the gravitational potential difference. The gravitational potential difference acts on the mass and the mass that falls in the gravitational field will gain some potential energy. Similarly an electric field electric charge that falls in an electric field will gain some potential energy, ok. So when we are talking about circuits we will not worry about potential energy or electric field we will talk only about the potential difference, ok. Ok it looks like the connection has been broken for some people or the quality has been questionable. So what I will do is I will just pause the camera to conserve the bandwidth and hopefully things will be better. You can give me feedback on whether it is indeed better, ok. What I was saying here is that I was trying to make an analogy between voltages or potential differences Oh yeah Video is off No that is what I mean people said Ok. So the video is off now by the way. What I was saying here was that I was trying to make an analogy between electrical potentials and gravitational potentials that you are familiar with. Here on the left side I have shown the earth and the gravitational field pointing downwards and if you place a mass somewhere it will fall down in the direction of the gravitational field and it will gain potential energy. It will always fall from a region of high potential to a region of low potential. Let us say it falls from a height h1 to a height h2. It gains a potential energy which is m times g gravitational acceleration times h1 minus h2. Analogously in an electric field shown on the right side electric field pointing downwards if you place a charge q somewhere it will fall that is it will move in the direction of the electric field and let us say it falls from one point where I have marked the potential of v1 to another point where I have marked the potential of v2 it gains a potential energy which is q times v1 minus v2 ok. So the amount of potential energy gained is proportional to the charge and it is charge times the potential difference just like the amount of gravitational potential energy gained is mass times some difference and it is the difference between some quantity at the initial point and some quantity at the final point. So what I want to emphasize here is that the voltage or potential difference makes sense only when measured as difference between value set two different points ok. There is not much significance to saying that the potential at particular point is one volt without saying with respect to what that potential is ok or in other words you have to say that the potential difference between point A and point B is something. This is something you have to do in circuits as well as the voltage is always measured between two points ok. So in fact while you are discussing it among yourselves or thinking about it you should always think of two points between which the voltage is measured. Lot of confusion about voltage comes about because you forget that it is measured between two points ok. So any questions about voltage any questions about voltage ok. There are a number of questions one was related to electromotive force and voltage ok. These are basically different terms for the same thing. Electromotive force is a somewhat old term and we use the term voltage now and somebody asked what happens if the field is in opposite direction or if the charge is negative. Now if the field is in opposite direction it will cause a potential in some different way ok. Now as we said as I said earlier we will not worry about fields we will only work with potentials and if the charge is negative whatever happens to the positive charge exactly the opposite will happen to the negative charge. A positive charge falls from higher to lower potential and a negative charge falls from lower to higher potential ok. Now one of the other questions is I said that the potential energy gained is Q times V1 minus V2 so how do we know V1 ok. Now when you talk about potentials in a field you will measure V1 with respect to infinity but it does not matter what it is measured with respect to ok. So if V1 and V2 change by the same amount it does not matter to anything ok. So it is only with the value of V1 minus V2 that matters. Now this will become more clear when we go on to discuss particular elements because we will only be discussing voltage differences across the elements ok. Now there are also number of other questions on interaction between charges and fields that we will not worry about and we do not have to ok. Our goal here is to do circuit analysis. So we can analyze circuits by staying at the level of voltages and currents without going into the fields ok. Now there are some laws that govern voltages and currents in a circuit ok. Now as I said I have not even put on what circuit it is. These are very general laws that apply to any circuit ok. This is you can think of them as basic properties of voltages and currents ok. Now one of these that talks about currents says that if you have a number of branches number of wires connected to a single point such a point is known as a node ok. And these do not have to be just wires there could be some elements right now we will not worry about what they are ok. Now what this says is that if you measure currents flowing out of the node ok. I will choose to measure the current in this direction. I call this I1, I2, I3, I4. So there is a law that says I1 plus I2 plus I3 plus I4 equals 0 ok. Now this has nothing to do with any particular circuit but this is true for any circuit ok. And this I think many of you already would know this is known as k-cops current law ok. So briefly could you tell me the conditions under which this is true is this always true under any circumstances or are there some conditions ok. There are a number of responses I have broadly grouped them into always true and for linear elements circuits and somebody said something about no resistance in the wires and then somebody else said charge conservation or no charge accumulation and so on ok. Now it turns out that of course this is not correct if I mean that is the reason I ask the question. Now this is a kind of funny answer because I have not even put down what circuit it is right I already said that these are critical properties of currents it has absolutely nothing to do with what circuits we apply it to ok. So this is something also important for a different reason I think whoever answered these things are mixing up some different concepts linearity refers to voltage current relationships or different elements. Now the k-cops current law that I am discussing here has nothing to do with what circuit it is ok it is generally true of all circuits or with some conditions as we see and again this also is something similar it has no resistance in the wires again it has absolutely nothing to do with that because you could have wires and you could have elements connected to it which could be resistance ok. Because if you said no resistance at all then such a law or such a theorem would not be very useful ok because it has to be useful for real circuits. Now finally we come to the main point which is that it is charge is conserved that is charge is neither created nor destroyed and more importantly it is not just this that is important there is no local charge accumulation ok that is you have current flowing out of it now if the sum is more than 0 that means that this charge was depleting from this point and if the sum is less than 0 charge is getting accumulated at this point ok neither of it is true so charge is conserved of course and also charge is not accumulated locally in any point ok so this is the reason why this is the assumption under which Kirchhoff's current law is true in fact there are conditions where it is not true if there is time we can discuss those things later but now for a large number of circuits this is true and we can use Kirchhoff's current law safely ok so that is true again as I mentioned earlier very useful analogy for thinking about currents is fluid flow ok so if you have a pipe here and then it branches off into two pipes it is very obvious I mean even without analyzing to most of you intuitively obvious that if there is water flowing here and then it will branch off into two and let us say here at a rate of 10 liters per minute now whatever the rates here are I mean this pipe could be big and this could be small and all of that so this is flowing at some rate R1 and this is flowing at some rate R2 you know that R1 plus R2 equals 10 liters per minute ok or if I have to use the convention and for currents I took all the flow to be away from the node so I can also take R1 liters per minute flowing that way R2 liters per minute flowing this way and this way it is minus 10 liters per minute ok it is a slightly weird way of saying it but a useful way when you talk about currents I initially assume that the flow is that way but it turns out that the flow is from left to right so that means from right to left minus 10 liters per minute are flowing ok so minus 10 plus R1 plus R2 will be 0 ok this is something that you intuitively feel is through ok even without knowing a great deal of flow dynamics and so on ok and why does this happen if this was not the case water would be accumulating here or water would be drawn out of here ok if we had a tank here into which water is accumulating this could not this need not be true ok for instance I could have water and then flowing into a tank and then nothing coming out of it whatever is coming here is going into the tank this is analogous to charge accumulation and we assume that such a thing is not happening as long as that is not happening this Kirchhoff's current law is true some of all the current flowing out of a node or equivalently some of all currents flowing into a node will be 0 ok a very useful thing and in fact a necessary thing to solve for circuits similarly there is something that governs voltages in general ok so let us say you have an electrical circuit electrical circuit means that there is some loop of electrical components now we have not even discussed any element but I will take some 2 terminal elements 1, 2, 3 4 and 5 ok and I will measure the voltage across each one like I said voltage is potential difference between 2 points so here I will measure v1 in this direction and here I will measure v2 in this direction please mind the directions in which I am writing this v3 here v4 you see that I am taking all the differences in the same direction and v5 ok again this has nothing to do with the specifics of the circuit and there is a law that says that v1 plus v2 plus v3 plus v4 plus v5 equals 0 and this is known as dead corpse so it appears that the audio was broken what I was talking about was the sum of voltages around the loop being 0 so here I have shown it for this particular circuit v1 plus v2 plus v3 plus v4 plus v5 equals 0 that is sum of voltages around this closed loop is 0 so all the voltages being defined with a consistent polarity you see that they are all in the same direction around the loop and this is known as kickoff voltage law the response I would like from participants is to tell me the conditions under which this is true again I have got a number of responses ok now some of you said that it is true in a closed loop yes of course it is only the closed loop that I am discussing I have written a loop and as I have written on the side sum of voltages around a closed loop equals 0 so my question is is that violated in some condition ok now it turns out that it can be violated if there is significant time varying magnetic field cutting this loop ok so this loop has certain area so this loop can enclose certain time varying magnetic fields if there are time varying magnetic fields in the cutting the loop then the sum of voltages does not have to be 0 ok so again all the practical situations or most of the practical situations that we encounter the time varying magnetic fields cutting this loop will be small enough cutting our loops will be small enough that we can take the sum of voltages to be exactly 0 ok ok so again this turns out to be true in a practice in a lot of cases so we can use the kickoff voltage law also safely ok now there are some people asking questions on what happens if voltages are induced from other loops that is exactly what I am saying that if there are time varying magnetic fields there will be the sum of these things will not be 0 it will be related to the rate of change of magnetic field and the area of the loop so we will not consider those conditions we will only consider the condition where the flux is 0 that is time varying flux cutting time varying magnetic field cutting the loop is 0 ok so we have these two basic laws and kickoff's voltage law and kickoff's current law one relates to voltages in a loop and one relates to currents in a loop and one of the very important things while applying this is to apply it with a consistent polarity ok so here I will show a loop the loop will have some elements but I will not worry about those or maybe I will show it with elements so that there is no confusion so if you look at this what I have done is to go this way ok if I go in a clockwise loop I always have minus first and plus next and so on ok in the direction in this direction ok as long as there is going in the in this direction and then I sum all the voltages it becomes 0 similarly for kickoff's current law at a node the sum of all currents flowing out of a node is 0 so I suggest that right from the beginning you adopt a consistent polarity because if you make a mistake with the polarity of these things obviously you will get the wrong answer ok now one thing I have to mention about what it is I did this for currents that is I told you that a current 1 ampere flowing from a to b is exactly the same as a current of minus 1 ampere flowing that way and similarly if you have 2 points let's say x and y and having a 1 volt difference in this direction is exactly the same as x and y and I will measure with respect to x the voltage in this direction being minus 1 volt so this is just so that you are comfortable with the sign convention so again for instance I could have some 2 points and I will write v1 this way this does not necessarily mean that this is at a higher potential than that it says that it is higher by v1 and v1 itself could be positive or negative ok so I think in today's lecture we have discussed a number of things basically definitions of voltage and currents and the laws governing them ok and we will continue from here in the next lecture there are a couple of more questions some of them are related to frequency of the voltage and so on I will not discuss those things here as they are not really relevant ok because even if let's say v1, v2, v3, v4 or time varying because voltage law says that at every instant of time the sum of those things has to be 0 ok similarly for the currents now the sum of currents i1, i2, i3, i4 is 0 for this particular example here ok now this is true even if those currents are time varying they could in general be time varying and every instant of time the sum has to be 0 ok so that is the meaning of current law now there is one very interesting question which is what are the circuits that do not know whether it is voltage law or current law ok are there common examples now it turns out that there are there is also so there is one very common example which is basically if the dimensions of your circuit are very large now by very large what do I mean very large compared to the wavelength of the signal then these things do not hold good ok we can perhaps elaborate on this later what I mean by that is let us say I have a really long wire ok and again I will think of positive charges flowing this way now always we think of charges flowing instantaneously but we know that it moves at the speed of light ok at least it is limited to the speed of light it can only move slower than that now let us say that you drive a current and you reverse the direction before the current can get from here to there ok because there is always some length to the wire and then it takes some time to get from here to there and before that if you reverse the direction of the current so let us say you are driving a current from one side you have to worry about how to do it before it gets from here to there the charge gets from here to there you reverse it then you look at different parts of the wire they will be carrying different currents ok and a very common example of this is the antenna I think all of you are familiar with antennas which are just single wire it could be sticking out of your radio or your car it is just sticking out and you will drive a current into it it looks like it is just hanging in the air so clearly Kirchhoff's current law is not valid here what really happens is that the length of the antenna is comparable to the wavelength that is before the current reaches from one end of the antenna to the other the direction of the current driving it changes and then so you have a consistent situation without Kirchhoff's current law being violated ok we will only be talking about those situations where the dimension of those circuits are much smaller than the electrical wavelength of the signals that are driving it so in our cases Kirchhoff's current law will be valid and similarly for Kirchhoff's voltage law so in general these things can be violated if you have a very large circuit and large relation to the electrical wavelength or in general if you increase the frequencies of the signals ok any questions ok so there are so there are some general questions which we will deal with later so in the next lecture what we will do is take some electrical circuit elements which are commonly used discuss their relationship between voltages and currents what we did today was to see general properties of voltages and currents and their definitions ok so in the next lecture we will look at some elements and then make some simple circuits out of them thank you everyone's posted it will have a definition forum where we can ask questions that will be moderated ok and there is an announcement also the online courses website with the recorded lectures and it will have a forum for you to post questions where I can post answers or perhaps others can also do that and so on ok and it will also have the syllabus and assignments and all of those things ok so please consult the online forum so and this class this lecture there were some glitches I think from the next lecture onwards things will be a lot smoother thank you


The Russian National Guard can oust Putin from power. President Putin wants to turn Russia's National Guard into his own army for domestic use, a top Kiev official has claimed, according to the Kiev Post. Mykhailo Podoliak, chief advisor to the Ukrainian presidential office, said Putin was severely weakened by the aborted Wagner coup against the Kremlin and is now taking steps to shore up his power. After Prigoshin's foiled riot, Putin proved that he is not a Tsar, but a jester, a coward, unable of decision making, tending to flee. He said on the telephone in comments reported by Espresso TV, Russia doesn't love him anymore. That's it, Putin's no longer sacred. Podoliak said that eventually the move would backfire and the National Guard could turn against the Russian leader because people in Russia love a strong Tsar. He added this would not happen immediately as at the moment a political group has not been formed that could seize power and replace Putin. Podoliak's assessment comes after Russian lawmakers passed a bill that would allow its National Guard to deploy heavy weapons, including tanks, on the streets of the country in the wake of the short-lived insurrection by the mercenary group Wagner. Since it was formed in 2016 as a means of controlling and stopping public demonstrations, the National Guard's role has since taken on a broader remit, including participation in Moscow's full-scale war on Ukraine. According to the legislation passed by parliament's lower house, the force, which answers directly to Putin, will be able to be armed with military-grade weapons, including heavy weapons.


So you've got a character sheet all written out and a couple of friends who want to play D&D, but you're missing one vital component. The world, the characters, the laws of physics everyone's gonna break to make for cool moments. You'll commission artists on the internet to draw for you.  Despite all that, such a title has an extremely low barrier to entry and is probably the most important thing at your entire role-playing table. And without one the game will not exist. So anybody and everybody should perform the duty at least once for the sake of their fellow players begging for a chance to experience this wonderful pastime. So long as I don't have to be the one to do it. What? Welcome to a Crap Guide to Dungeons & Dragons! The Dungeon Master or Game Master if you like clay in your soup is the mind behind the magic and who decides just about everything that happens in the game besides the player's own choices. Your role as a DM is to control and describe literally every single little detail that happens during the game as you are the game. The game cannot exist without a Dungeon Master. As the DM you call the shots based on how the rules work or if you don't like the rules and say shoot that poot and come up with your own. Otherwise, how else are you supposed to know if your rules lawyering players giving you correct information and isn't just making an elaborate manipulative plot to trick you into giving them a pet displacer beast? Fortunately for you, if you aren't sure or don't remember how a certain rule works, you can always just look it up because being a good DM is about applying information, not memorizing it, unlike the American education system. Outside of the rules, though, you are the bridge between the players and the fantasy world they're playing in, describing everything that's going on in excruciating detail like a radio show but with a lot more awkward pauses. Everything they fuck, marry, or kill is through the context of how you describe it, which means you have to be incredibly deliberate with your vocabulary and respect the Oxford comma, or else you might make the wrong translation of what's going on in your brain to the players who may then think the innocent bystander in DC is actually a murderer because you accidentally stuttered when voicing them saying they were just doing their tasks. There are quite a few ways information can be put across to the players and it all comes down to the DM's preferred style of presentation. Many pop culture depictions of the nerd ritual often show an ornately carved and treated mahogany table. Players dressed in professional cosplay on par with 2000s Hollywood costumes, atmospheric mood lighting that'll make a hardcore dom blush, background music and ambience that's like a spa day for your ear canals, and detailed miniatures, maps and set pieces painted by angels using brushes made from the nose hairs of the gods. Now, do you need all these fancy, expensive, and superfluous amounts of presentation and stimulus in order to have a worthwhile Dungeons & Dragons experience for your players?  But even with all the fanciest of theatrics, every Dungeon Master has to rely on the ever-prevalent theater of the mind, where everyone has to use their imagination to visualize what's happening in your grand spankin' fantasy world. So a game of D&D doesn't have to cost hundreds of dollars and can be anything from a massive theatrical event to a hangout with the bros with cardboard cutout minis to even sitting in a restaurant with napkins for character sheets and the salt and pepper shakers are the evil queen of spice and her angry white steed. No matter what, you'll always eventually have to rely on the most useful creation of all mankind that can raise armies and fell nations. Words. Never underestimate the power of a good the source because inevitably there will be a situation where all your fancy props won't suffice and you will have to learn how to use old English vernacular. As the DM, you'll have to learn how to use old English vernacular. As the DM, you'll have to learn how to use old English vernacular. As the DM, you'll have to learn how to use old English vernacular. As the DM, you'll have to learn how to use old English vernacular and most of your responsibility all boils down to allowing the players to interact with your grand spankin' fantasy world. And how they do that can be summarized in one simple action, rolling dice. When a player wants to do something, anything, the DM is the one who decides if the player rolls dice, what dice they roll, and the outcome of the roll of the dice. Then, just about everything else is an extension of that one single responsibility, which is why nobody wants to do it, because one single responsibility is far too many. An extension of that, the DM's the encyclopedia of the D&D game. If there's history in the world, it's the DM's job to know it. When the players are fighting bad guys, it's the DM's job to keep track of the enemy's abilities, hit points, and sexual orientation. Just in case, you never know. If a player resurrects their long dead uncle, it's the DM's job to have read their backstory to know said uncle was a drunk rocketeer who eats horseshoe crabs. And when the players bring up how the plot and characters are oddly similar to Lord of the Rings, it's the DM's job to kick their ass. The scariest part about being a Dungeon Master, however, is the improv. Since you can't anticipate every single possible possibility the players can possibly make possible, you have to think on the fly and figure out how those possible things could be possible. If the player character tries to eavesdrop on somebody, you have to come up with what they hear. If somebody eats too many beans and farts, you gotta come up with how it smells. And if the party decides to run off some other direction rather than the main plot, you have to come up with what they run into. Like another town, or a dangerous hag, or even the main plot. Because you moved it over there, since the giant glowing breadcrumbs in the shape of story progress this way wasn't obvious enough.  Somebody at some point in time will do something that'll turn your no pants bad dreams into a reality and you gotta figure out then and there whether you're gonna get a new pair or just roll with it while the player see your metaphorical junk swaying in the breeze. So with all that easy to digest and totally not intimidating stack of expectations that doesn't even scratch the surface of what it takes to be a Dungeon Master out of the way, the question now becomes how does one even start being a Dungeon Master? Just do it! No matter what, you'll want a copy of the player handbook since it has a majority of the most common rules. As far as actual content goes though, the most baby friendly way is to purchase a pre-written adventure, one of these buggers, which will usually have a plot, characters, encounters, villains, and plenty of faffing about material for your players. However, if that's too much punishment on your wallet, the natural safe word is making a campaign of your own. The thing about safe words though is it often stops things in their tracks so it will require you to come up with most of the aforementioned plot, characters, encounters, villains, and faffing material yourself, which can take anywhere from a knight of binge writing to never because you only ever think about your ideas and never write it down.  And as anyone who's taken biology can tell you, organs are gross and messy and can often go misplaced so you just have to substitute a kidney with a moldy sponge for a bit while you go find it. Until suddenly the blood cells start making friends with the sponge and it becomes more effective than an actual kidney and you start to question everything you've ever learned in school.  Do you spend entire weeks drawing maps, writing possible paths, and dialogue options for characters down to the description of their cousin's boyfriend's dog's favorite chew toy? Or do you just spend the week doing some faffing about of your own and then spend the final half hour leading up to the session time frantically writing down bits from a D&D random content generator. But hey, once you get a game going the rest should come naturally. Just take it all one step at a time and you can especially relax whenever the players start to role play and act on their own. Because then you can just sit back and relax and let them have their fun and you don't even have to do dialogue for any NPCs or lord dump on them.  Yes, the dirty wails underbelly of being a dungeon master is dealing with the barnacle infestation that is being the de facto babysitter of the group and then you gotta bring out the scraper of social obligation. In some situations more than others the DM is expected to have a significant amount of say in organizing the playgroup since you have something of a larger leadership role for the game to exist than the players. You're who the players will look to when arguing over who gets the loot.  This means that you cannot take a passive role as a DM.  With all of that said I still could not possibly cover the grand mountain climb that is explaining what it takes to be a dungeon master. Not to mention what it takes to be a good dungeon master. And I've seduced enough tall folk to make Kanchenjunga horny for me. But I believe the best possible way to show you what it takes to be a dungeon master would be a demonstration of those undergarment, moistifying skills I possess.  Alright, unexpectedly, as you walk into a tavern a crowd is gathered and everyone seems to be having a good time. I'll accept the mysterious hooded figure in the center of the room that nobody except you all seem to notice. What do you do? I wanna smash the barkeeper! I want to smash the barkeeper. Nobody wants to have a chat with the hooded figure? Who knows? It may tie into one of your backstories. Oh yeah, that reminds me. DM, could you look over these notes I have about my backstory? It's only a few pages long, but I wanted to make sure to keep the authenticity of my homeland as the center point to my character development.   I'm not reading all of this. Oh yeah, speaking of, I wanted to check in with you about this new homebrew I created from one of my backstories characters. I ran it by a couple of friends and they seemed to think it's pretty balanced, so no need to worry about looking over it too much. Oh no no no no no no no. I know what you're trying to do, you scruffy looking. Hey DM, are there any goliaths in the tavern? No particular reason, I just wanted to know. Dude, yeah, are there any? I've been looking for a surfing buddy for some time. We're at the beach, right? I wasn't really paying attention, could you set the scene again? Bah, whatever, I'll get back to you guys later. Dawnright, have you made up your minds about that ambush yet? That guy you've been targeting for the past three sessions is right there enjoying his dwarfish drink. Oh boy, I surely am enjoying my dwarfish drink. Look, whenever we take a single decision like going to the left or to the right, it goes wrong. We need to have a hundred percent flawless plan. Oh, maybe we can talk with him? But if things go wrong, I can use my gun.  I don't remember giving him a gun. Has he always had a gun? Just one guy. Why don't I just sneak up on him and poison his drink? I have a plus 10 to stealth, plus advantage with my cloak of invisibility, and add on another 10 if Ron's uses his pass without a trace. No one will ever see me, and we can avoid this whole encounter. Or I can use this gun. How many times must you terrify my sweet bottoms? You upright marsupial! I'll give you six minutes and 44 seconds. If you don't come to an agreement on a plan, I'm feeding your minis to the Wigglers.  They gesture towards five open seats and say that you should go- So who's the most expensive looking dude here?  There's a noble in the corner of the room, sure, but he's busy talking with somebody else right now, so maybe you should probably- I'm already there. I intimidated him to challenge me to an arm wrestling match for all his golden belongings. Hey, absurd. You could use Charmed Person. I mean, that would cause the Charmed Status, which would give you advantage on any social- I asked him to give us all of his money. Absurd. I rolled an 11. That's really more of a help action, which actually- What the fuck? I didn't even ask you to roll yet. But I did it already. Look, an 11 is good. We are friends now. Everyone likes Absurd. I intimidated him to challenge me to an arm wrestling match for all his golden belongings.  You start to arm wrestle him for some of his gold. Oh, I already stole it all. Also, he might be cursed, cause, you know, back story stuff. Alright, sure. In the meantime, the hooded figure in the middle of the room that everyone decided to totally ignore transforms into a massive towering titan and the roof of the tavern is blown off, revealing Evilous Maximus, the demon lord of darkness. Evilous Maximus? Now, my Latin's a little bit rusty, but that name seems a little bit on the nose. It sounds to me like he's actually ripping off the Pope's title of Pontifex Maximus, so maybe we should be on our guard for some vile bishops and dastardly cardinals. No, he's not.   What? This is outrageous. This is unfair. I demands to roll an opposing skill check. Ooh, this is the classic weaken your opponent before the showdown strategy used by the really ego maniacal bad guys. He wants to demonstrate that we're over-reliant on our magic items as a sort of condescending attack on our self-worth.    Ooh, textbook orb strategy. Stop making comparable analysis. Evilus then casts hold person on all patrons of the tavern. Everyone needs to roll a- Counterspell, counterspell, counterspell. Hey, did you see this new ad for an over-the-table dictionary? What's it called? Counterspell.  All of them. No way you really don't have that many. Of course I do. Bullshit, let me see your character sheet. No. Let me see it. No. Let me see it, Dabby. No. Get it to me, Dabby. I'm a fighter, sorcerer, multi-class. I'd like to use my beast movement to carry me to the enemy, then have them attack the enemy, then use my familiar's action to use the help action, then cast Haste on myself, cast Eldritch Blast as a quicken spell, use action search to put a light on my beast's nose, and attack with my hasted action. Oh, sweet. My shield guardian spell procs, because he targeted me with a spell, so that's gonna be a faithful hound right on Evilus' heels. Now that it's my turn, my sweet sweet pup is definitely gonna have a munch, and then I'll have the guardian run up and slap him, and then I'll use my ninth level spell slot to conjure... Wait, hold on. 32 enormous constrictor snakes. Hi. You're keeping track of all these initiatives, right? Uh... Fuck. Don't forget that I also have two horses, a mastiff, and six chickens. Oh, actually, I still have my movement. Can I dodge as a free action? The dog's name is Cheese Puff, by the way. Joel, can I play this? Um... Well, you two sort that out. I'm going to try to scam as many people as possible out of their coins. Hold up there, you oversized crow. You said you were lawful good. Oh, no, no, no, no, no. I said I was a half-elven town guard turned hospice nurse and non-lethal hedge knight. But, you know, I can understand the confusion. Besides, I don't believe in alignment anyway. I'm trying to get my scam on, thank you. Ladies and gentlemen, may you lend me your ears. I have here in my hand one of the finest crews in all... Okay, so as I stand up in a chair, everyone looks at me. I smile charmingly, and everyone starts cheering already. As I pull out a 12 chord ukulele. Excuse you, who's the DM here? Oh, you, of course. But in this scenario, I will have to roll persuasion or performance. And if I pass a DC check 15, I will charm everyone around me into following my every command. Doing this will allow my character to start its own company, creating profits through the selling of a very specific... No. Don't worry, everyone. Just think of all the friends we've helped through our journey and the ties between our hearts that will help us defeat Evilous Maximus. In the name of Saloon, I will punish you! Believe it! Can I stab her and take all her stuff later? Hey, DM, not that it actually happened, but hypothetically, if I lost a die set you let me borrow, would you happen to have another one? I swear, I just... Oh, I have the perfect theme music for this exact situation. Just hold on one second, I'll find it. Music! Good idea! My fur ball pulls out there ukulele and begins to sing to the villain.  We're two of a kind, two sides of the coin. Well, I got no tail, I could give you some... Alrighty, I think that's enough barting for now. I said that's enough. I feel as though we haven't really sussed out the emotional stakes here.  He's the demon lord of darkness. He murders people and is awful and terrible and bad. Or is he perhaps a metaphor? A construct representing the lasting woe that persisted after the age of reason. Or maybe we are all Evilous. He's a reflection of our own inner...  You know, we probably can't even take Evilous. According to the strategy guide, he commands four Krakens made of like pure gold, which are actually waffle neutral by the way. So they're technically not even evil and they just serve an evil lord, which is interesting because... Hey, stop reading the official campaign setting! What was he funding all this? I think I have a... I'm sorry, I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry.  I should make putting pretzels tonight. Evilous Maximus has you all completely surrounded and begins to speak. Foolish mortals, I've lived for a thousand lifetimes and once I'm done with you, I'll continue to live a thousand more.  I fail in gods and consume the world. Worlds which you all have pales in its own inadequacy. For the darkness I've tamed is... We've got him now, guys. I cast Polymorph in the middle of his speech. Yeah, yeah, turn him into a T-Rex. No, wait, T-Rex is back. Okay, I'm gonna grab pretzels. I'm gonna do a magic spell.    I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. I'm sorry. That is it!   No, you can't talk to the barkeeper. They ignore you. I didn't read your backstory. Your homebrew's rejected.  No, I'm not gonna describe it again for you. You all took too long so your ambush fails and you fall to the floor of the tavern. All's your target runs away. I never ask for a single one of you to roll, so all your dice go to waste. You don't get that gold.  You two stop comparing my totally original campaign to popular and historical media.   Nobody listens to you and the guards show up to arrest you for disturbing the peace. Hey, it's alright, JoeCrap. There's no need to get so hostile. If you just take a moment to talk to the players, I'm sure we can all- Nobody cares, Matt Mercer. No, no, no, and no to all of your plans. An evilist maximus doesn't get interrupted by your spell.  Fine, whatever. Leave. I don't need you. I can find some other players who would be happy to play the game I meticulously plan for them.  This is what you get for ruining the scene. It's all your fault, you know. You're welcome. Satisfied?  If they don't want to play the game I've set up for them, then they don't deserve to play at all. Maybe, but did you ever think about the game they do want to play? You know, the players are just as much a part of how the session goes as you are. Part of D&D is about how anything can happen. But I planned out this whole thing for them. I even got all the books and everything.  That's true, and maybe they never will, but that might be okay. Sure, keep in mind where you want the game to go, but not everything has to be by the books. Everyone is playing their own version of D&D, and as the DM, you have to be able to adapt to that. Saying no to everything you don't want them doing isn't going to give them an amazing experience with infinite possibilities. It's just going to make them feel like the game's better off without them. But what if I do let them do whatever they want, and things go wrong, and it gets boring or imbalanced, or forget something important, or the game goes south somehow, and the players don't like the session anyway, and then you go again and do better next time. In this situation right here, it could be a good start. Yeah right, and what am I supposed to do? Talk to the players? You can certainly try. Guys wait, I'm sorry. I was worried that if you didn't play the way I wanted you to, that the game wouldn't be as cool or as fun as I thought it could be. I was too constricting on your agency and shouldn't have stopped you from at least attempting to do the things you wanted. And I should have talked with you and maybe come to some sort of compromise on some of the things I was really stubborn about. Being the dungeon master is just really, really scary. There's so much I have to keep track of. Coming up with things on the fly can be really hard, and I want to run the best game I can for everyone. And I'm terrified of messing things up. So sometimes I can get a bit vapid and mature and atomically confusing. Aggressive. But I'm willing to try again if you are. So how about it? Would you like to play some D&D? So, Krabby, you were saying you wanted to interrupt Evilus Maximus. Uh, yeah. I wanted to cast Polymorph on him in the middle of his speech. All right, what's your spell save DC? Um, 15. Against all odds, you successfully polymorph Evilus Maximus. He transforms into a meek little sheep and falls to the tavern floor.  Everyone, roll for initiative.


I think we're going to get started. I think folks will still probably straggle in over the next, I would guess, about 15 minutes. We'll see a couple more bodies, but we can get started if everybody's ready. Okay, everyone has their last coffee? Okay. So for people who weren't with us yesterday, I just wanted to explain the format. So for the breakout sessions, the people who are running breakout sessions will come up and pitch their talks, and then we will tell you where they will be, and then we will break for those breakout sessions. And that is the majority of the day-to-day, our breakout sessions. After lunch, we have a future of the internet keynote, or internet, if you want to call it that, from Malka Older, who will be joining us later today, and with her keynote we'll do actually a workshop as a full group, I think, in here, which we will share more about later. Other things, any questions about logistics of the space? I think people know now the bathrooms over there, there will be food, there will be lunch later. Please eat, switch sessions as you need to, and feel free to come find me and ask questions if you have any. I'm Georgia, by the way, for those of you who don't know me. Okay, so with that then, can I ask, I think Yaa and Chris are giving their pitches. One change to this morning's program, one of the sessions, which Shazna was doing on linear Asia's research, is going to be in the second session in combination with research ICT Africa. So there's just two sessions in this first morning breakout, so, Yaa, do you want to come up? There you go. Okay. Hi, my name is Yaa Chang, I'm a software engineer with the Google New York City team. I'm here to talk about penetration of data, the history and the future, how we process the data, how we monitor the data processing, and how we will improve the data usage using new binary and new schema. So, this is a brief history of Patrick's Out that's currently running on MLM platform. The original paper was written in 2006 by a teamer's team from Paris. So the name is Paris Traceout, which sent a reverse route probing request from the server to the client and tried to get the pass as much as possible. So it resolved the several critical issues like diamond pass, how to make sure the pass is crossing the different areas and record the time and the protocol. So it's wildly recognized as an efficient transfer out algorithm. We start to collect data from 2013 till now. So the output of our data published in two kinds of format, the raw data stored on Google Cloud Storage on this address for data before 2017 June. And after 2017 June, we move the new data to a different bucket. The ETL pipeline will pass the data into schema format on BigQuery table and available for search. So this is the BigQuery location for the Patrick's Out data. Now our platform is 100% open source. You can reproduce all our data using the open source code we published. Here is a brief figure describe the amount of data we have collected for more than half a year, more than five years so far. Totally we have more than one billing test in our BigQuery table. Each hop will become a separate role. So we totally have roughly 18 billing roles in the BigQuery table. And this is the older version, but it's fine. We have roughly eight billing roles added for the first half of this year. And we expected to aid more than 17 billing roles in 2018. So the data is considered increased. We have a huge amount of useful information that will be super helpful for all kinds of research. And I will give an example of how researchers use our data in their work. And the future PT data usage in my session. If you are interested, you can come to see my talk over there. Chris, who's giving the devices one? Chris, you're right there. Can I see your hand? That's fine. Thank you, Georgia. Wow, that's exciting. I wish I could come to your session. I'm excited. I was just talking to Peter. That's a very rich unexplored data set in Paris for researchers who might be interested in that. So I am doing a talk this morning with Ross Shulman, my colleague at OTI in the back there. And Simone Basso is over here on the side. And we're going to talk about device-based measurement. What is device-based measurements? Well, you know, one of the things about I think that some people complain about NMLAB data is that the crowdsourced nature of the data is sort of not like structured research. But it's possible to do both, and I think there's value in both. And device-based measurement is sort of what we're pursuing along the lines of that in various ways. So we're automating measurement from small computers, running code, consumer devices, so allow different researchers to run test data in a structured way, collect a data set, use it for specific research using the NMLAB platform, so taking the non-crout source approach to a more research-centric approach, standardizing the hardware. So I'm going to talk about that. Sorry, I'm just trying to hit the, see the screen here without glare. You can walk closer to it if you can use this one. Oh, thank you, Jordan. All right. Yeah, and it just, there it is. Sorry, yeah. The brain cells aren't really, synapses aren't really connecting just yet. Coffee will be easy. We're going to talk about devices. I'm going to talk about running research projects with devices. Ross is going to talk about, I'm going to talk about doing that using like an IoT-style platform, so automating the deployment and management using a platform called Resin. And Ross is going to talk about Markami, which is a sort of stand-alone version of that, which we were hoping will eventually be kind of the thing you can download and use at your home. And then Sor Simone is going to talk about the software that he has written called Measurement Kit, which is the library that undergirds both of our Ross and I's work on these projects. Measurement Kit is a software library that basically abstracts a lot of measurement tests and allows embedded device developers and others to just compile that code and run the binaries and collect the data.