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edx-platform/common/test/data/full/subs/eLAyO33baQ8.srt.sjson

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"text": [
null,
"SPEAKER 1: In this sequence, are\ngoing to look at a whole",
"bunch of techniques for\nanalyzing circuits.",
"Think of these as your tool\nchest. So you are embarking on",
"6.002 and going on to build\nlots of useful electronic",
"systems.",
"But before we go and build these\nsystems, much like a",
"carpenter who needs to go build\na house, much like a",
"carpenter has to go and buy a\nset of tools from the local",
"store, we need to go and make\nsure that you have the tools",
"in your tool chest to analyze\nthese circuits.",
"This tool chest will include\nthings like the KVL KCL",
"method, the Node method\nand so on.",
"But before I begin talking about\nthese techniques for",
"your tool chest, I'd like to do\na extremely quick review--",
"as is my usual practice--",
"of what you've covered so far.",
"So remember our EECS\nplayground.",
"We've gotten into this place by\npromising that we are going",
"to observe the lumped\nmatter discipline.",
"By observing the discipline\nrecall that the complexities",
"of Maxwell's equations and the\ndifferential equations that",
"you have to solve-- the\npartial differential",
"equations-- goes away.",
"And you're left with very\nsimple linear equations.",
"And you will see a lot\nof that today.",
"As you make the lumped matter\ndiscipline, you end up with",
"these lumped elements, like\nresistors and voltage",
"sources and so on.",
"And what you do with these\nlumped elements is we can",
"label what are called the\nbranch variables or the",
"terminal variables for these\nlumped elements, OK?",
"So for example, v is the voltage\nacross the element.",
"And i is the current through\nthe element.",
"The power consumed by the\nelement is given by vi.",
"Continuing with our review, the\nlumped matter discipline",
"enables us to create the lumped\ncircuit abstraction.",
"So you take these lumped\nelements and you connect them",
"with ideal wires.",
"So in this case, I have a\nresistor which is a lumped",
"element, a voltage source.",
"And I connect them with\nthese ideal wires.",
"And what you end up with is\ncalled a lumped circuit.",
"But this is your lumped\ncircuit abstraction.",
"Well as we made the transition\nfrom physics to EECS by",
"adhering to the lumped\nmatter discipline.",
"I had discussed in the last\nsequence that Maxwell's",
"equations turn into very simple\nalgebraic equations.",
"And these are captured by\nKirchoff's voltage and current",
"laws, called KVL and KCL.",
"So KVL says that for all loops\nin your circuit, the sum of",
"the voltages around the\nloops add up to zero.",
"Similarly for all the nodes in\nthe circuit, the currents that",
"enter into a node\nadd up to zero.",
"And in the same matter, if I\njust summed the currents",
"leaving a node, they also\nadd up to zero.",
"So whether you sum the currents\nentering the node or",
"currents leaving a node, they\nwould add up to zero by KCL.",
"And the beauty of this was by\nadhering to lump matter",
"discipline, recall the\ncomplexities Maxwell's",
"equations whether an\nintegral form or",
"differential form went away.",
"And we were now left with\nextremely simple algebraic",
"expressions of the sort.",
"And you will see shortly that\nyou will end up solving",
"extremely simple linear\nequations",
"as we analyze circuits.",
"So as one example here\nis a linear circuit.",
"It has one, two, three, four,\nfive, six elements.",
"It's got a voltage source\nof a voltage v zero.",
"It's got a resistor, r one\nand so on and so forth.",
"So for this circuit according\nto our abstraction and the",
"laws of KVL and KCL,\nthe following",
"are going to be true.",
"So for instance if I look at\nnode a, then according to KCL,",
"the currents entering the\nnode must be zero.",
"So in other words, the\ncurrent here is ica.",
"And I can sum to that\nthe current",
"entering from the d direction.",
"So that would be plus ida.",
"And then there is a current from\nthe ba direction and iba.",
"Those are going to\nsum to zero.",
"Now I can multiply the whole\nthing by minus 1.",
"And that would give me the sum\nof the currents leaving the",
"node are also going\nto be zero.",
"So that is KCL.",
"Now I can also write KVL in this\ncase for this loop, for",
"instance, here.",
"For this loop I can add up the\nvoltages around the loop.",
"And by KVL they must\nadd up to zero.",
"So for example if I look at\nthe voltage vca, I can add",
"that to the next voltage here.",
"That is to vab and then\nadd that to the",
"final voltage, vbc.",
"And by KCL--",
null,
"so all of those must\nadd up to be zero.",
"Now if you go back to our\ncircuit here that you see on",
"the left hand side, I am going\nto show you a little demo that",
"will look at these currents,\nica, ida, and iba, and also",
"look at the voltages, vcabab\nand bbc and actually go and",
"look at the circuit, make the\nmeasurements, and show that",
"they indeed sum up to zero.",
"Not surprising.",
"KVL and KCL really work.",
"And so the demo should\nalso work.",
"OK.",
"So let's go and do our demo.",
null
]
}