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[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.27,0:00:05.03,Default,,0000,0000,0000,,Now let's talk about circuit elements\Nin a little bit different way.
Dialogue: 0,0:00:05.03,0:00:06.66,Default,,0000,0000,0000,,Let's talk about realistic voltage and
Dialogue: 0,0:00:06.66,0:00:10.70,Default,,0000,0000,0000,,current sources and i-v curves\Nassociated with common elements.
Dialogue: 0,0:00:10.70,0:00:11.56,Default,,0000,0000,0000,,Let's talk about open and
Dialogue: 0,0:00:11.56,0:00:14.97,Default,,0000,0000,0000,,short circuits and switches,\Nparticularly wiring three-way switches.
Dialogue: 0,0:00:16.05,0:00:19.15,Default,,0000,0000,0000,,An ideal voltage and\Ncurrent source has no resistance.
Dialogue: 0,0:00:19.15,0:00:23.58,Default,,0000,0000,0000,,The voltage source just produces voltage,\Nthe current source just produces current.
Dialogue: 0,0:00:23.58,0:00:27.82,Default,,0000,0000,0000,,But a more realistic non-ideal voltage\Nsource and current source has resistance.
Dialogue: 0,0:00:27.82,0:00:30.19,Default,,0000,0000,0000,,A voltage source has\Na resistor in series and
Dialogue: 0,0:00:30.19,0:00:34.06,Default,,0000,0000,0000,,a current source has a resistance in\Nparallel, called the shunt resistance.
Dialogue: 0,0:00:34.06,0:00:37.27,Default,,0000,0000,0000,,You know that most of your sources\Nare realistic because they heat up when
Dialogue: 0,0:00:37.27,0:00:37.91,Default,,0000,0000,0000,,you use them.
Dialogue: 0,0:00:37.91,0:00:41.22,Default,,0000,0000,0000,,Your power drill, for example,\Ngets hot when you use it very long,
Dialogue: 0,0:00:41.22,0:00:43.71,Default,,0000,0000,0000,,and that's because of\Nits internal resistance.
Dialogue: 0,0:00:43.71,0:00:46.68,Default,,0000,0000,0000,,Here is a graph of the internal\Nresistance of a battery.
Dialogue: 0,0:00:46.68,0:00:50.84,Default,,0000,0000,0000,,Batteries get hot when we use them too,\Ncertainly my laptop battery does.
Dialogue: 0,0:00:50.84,0:00:55.71,Default,,0000,0000,0000,,So you can see that this battery,\Nthis is an Energizer 1.5 volt AA battery.
Dialogue: 0,0:00:55.71,0:00:59.32,Default,,0000,0000,0000,,As the temperature changes, so\Ndoes its internal resistance.
Dialogue: 0,0:00:59.32,0:01:04.22,Default,,0000,0000,0000,,Its internal resistance is just going to\Nbe, oops, I want it to go up, not down,
Dialogue: 0,0:01:04.22,0:01:08.42,Default,,0000,0000,0000,,is going to just be this series resistance\Nthat's right here with a battery.
Dialogue: 0,0:01:08.42,0:01:09.94,Default,,0000,0000,0000,,So let's take a look.
Dialogue: 0,0:01:09.94,0:01:12.29,Default,,0000,0000,0000,,Now, if you were at room temperature,
Dialogue: 0,0:01:12.29,0:01:16.72,Default,,0000,0000,0000,,the internal resistance of that\Nbattery would be about 0.15 ohms.
Dialogue: 0,0:01:16.72,0:01:21.49,Default,,0000,0000,0000,,And if you were in Antarctica, which\Nis where I did some measurements, and
Dialogue: 0,0:01:21.49,0:01:25.28,Default,,0000,0000,0000,,let's say that you were about\N-10 degrees centigrade,
Dialogue: 0,0:01:25.28,0:01:28.50,Default,,0000,0000,0000,,then your resistance\Nwould be about 0.3 ohms.
Dialogue: 0,0:01:28.50,0:01:30.79,Default,,0000,0000,0000,,Let's see how that affects you.
Dialogue: 0,0:01:30.79,0:01:34.06,Default,,0000,0000,0000,,Let's suppose that you just want\Nto hook up this battery with its
Dialogue: 0,0:01:34.06,0:01:36.65,Default,,0000,0000,0000,,internal resistance to a very small load.
Dialogue: 0,0:01:36.65,0:01:40.28,Default,,0000,0000,0000,,I'm going to use a 1-ohm load for\Nthis example.
Dialogue: 0,0:01:40.28,0:01:43.92,Default,,0000,0000,0000,,I would find the current that's in\Nthe circuit by taking the voltage and
Dialogue: 0,0:01:43.92,0:01:46.50,Default,,0000,0000,0000,,dividing by the sum of the two resistors.
Dialogue: 0,0:01:46.50,0:01:51.37,Default,,0000,0000,0000,,So in this case, if I had an ideal source,\Nit would be 1.5 volts divided by my
Dialogue: 0,0:01:51.37,0:01:57.02,Default,,0000,0000,0000,,1 ohm load, and so I would have\N1.5 amps for the ideal battery.
Dialogue: 0,0:01:57.02,0:01:59.29,Default,,0000,0000,0000,,But now let's say that\NI'm at room temperature.
Dialogue: 0,0:01:59.29,0:02:04.08,Default,,0000,0000,0000,,In that case, my internal resistance is\N0.15, so if I add that right in here to my
Dialogue: 0,0:02:04.08,0:02:07.44,Default,,0000,0000,0000,,1 ohm, I'm going to have 1.3\Namps at room temperature.
Dialogue: 0,0:02:07.44,0:02:10.81,Default,,0000,0000,0000,,It's a little less than I had for\Nmy ideal battery.
Dialogue: 0,0:02:10.81,0:02:13.96,Default,,0000,0000,0000,,Now let's go to my Antarctica battery, and
Dialogue: 0,0:02:13.96,0:02:18.73,Default,,0000,0000,0000,,that's where I have 0.3 ohms\Nconnected on to my 1 ohm load, and
Dialogue: 0,0:02:18.73,0:02:23.17,Default,,0000,0000,0000,,I have 1.15 Amps,\Nthan I really intended to have 1.5.
Dialogue: 0,0:02:23.17,0:02:25.09,Default,,0000,0000,0000,,So what did that do?
Dialogue: 0,0:02:25.09,0:02:28.40,Default,,0000,0000,0000,,This is why our batteries went dead so\Nfast in the Antarctic cold.
Dialogue: 0,0:02:30.44,0:02:32.61,Default,,0000,0000,0000,,Now let's talk about I-V curves.
Dialogue: 0,0:02:32.61,0:02:35.96,Default,,0000,0000,0000,,Here are the I-V curves for\Nthe simple circuit that I just showed you.
Dialogue: 0,0:02:35.96,0:02:38.62,Default,,0000,0000,0000,,You have a battery\Nconnected onto a resistor.
Dialogue: 0,0:02:38.62,0:02:42.14,Default,,0000,0000,0000,,And what we would be plotting\Nis voltage on the x axis and
Dialogue: 0,0:02:42.14,0:02:44.93,Default,,0000,0000,0000,,current, or I, on the y axis.
Dialogue: 0,0:02:44.93,0:02:48.10,Default,,0000,0000,0000,,The I-V curve for\Na resistor is always a straight line.
Dialogue: 0,0:02:48.10,0:02:50.56,Default,,0000,0000,0000,,The resistor is a linear device.
Dialogue: 0,0:02:50.56,0:02:53.37,Default,,0000,0000,0000,,If I had a 1 kiloohm resistor,\Nfor example,
Dialogue: 0,0:02:53.37,0:02:58.00,Default,,0000,0000,0000,,connected onto a 1 volt battery,\NI would have 1 milliamp of current.
Dialogue: 0,0:02:58.00,0:03:02.19,Default,,0000,0000,0000,,If I had a 2 kiloohm resistor,\NI'd have half a milliohm of current.
Dialogue: 0,0:03:02.19,0:03:04.36,Default,,0000,0000,0000,,And if I had a really high resistance,
Dialogue: 0,0:03:04.36,0:03:08.10,Default,,0000,0000,0000,,let's say infinity,\NI would have no current at all.
Dialogue: 0,0:03:08.10,0:03:12.05,Default,,0000,0000,0000,,On the other hand, if I had a very\Ntiny resistor, let's say 0 ohms,
Dialogue: 0,0:03:12.05,0:03:15.90,Default,,0000,0000,0000,,I would have no voltage, but\NI'd have a very large current.
Dialogue: 0,0:03:15.90,0:03:17.51,Default,,0000,0000,0000,,What does that mean?
Dialogue: 0,0:03:17.51,0:03:20.34,Default,,0000,0000,0000,,Having a resistor of 0 is a short circuit.
Dialogue: 0,0:03:20.34,0:03:24.11,Default,,0000,0000,0000,,That's where my current runs away with me,\NI have a huge current, and
Dialogue: 0,0:03:24.11,0:03:26.05,Default,,0000,0000,0000,,my voltage would be 0.
Dialogue: 0,0:03:26.05,0:03:30.06,Default,,0000,0000,0000,,An open circuit has a very high\Nresistance, resistance of infinity, and
Dialogue: 0,0:03:30.06,0:03:33.84,Default,,0000,0000,0000,,in that case, you have no current,\Nbut you have a very large voltage.
Dialogue: 0,0:03:36.07,0:03:39.45,Default,,0000,0000,0000,,The I-V curves for an LED are non-linear.
Dialogue: 0,0:03:39.45,0:03:43.78,Default,,0000,0000,0000,,The LED is a little light bulb that turns\Non when we put a voltage across it.
Dialogue: 0,0:03:43.78,0:03:47.10,Default,,0000,0000,0000,,We're going to be using it in our first or\Nsecond lab.
Dialogue: 0,0:03:47.10,0:03:51.50,Default,,0000,0000,0000,,So you can see right here that there\Nare different colors of LEDs and that
Dialogue: 0,0:03:51.50,0:03:56.04,Default,,0000,0000,0000,,as the voltage increases for each one,\Nsee here's, I'm turning up the voltage,
Dialogue: 0,0:03:56.04,0:03:59.49,Default,,0000,0000,0000,,turning up the voltage, and\Nthe current becomes very high.
Dialogue: 0,0:03:59.49,0:04:03.92,Default,,0000,0000,0000,,This elbow right here,\Nwhere the current goes from being almost 0
Dialogue: 0,0:04:03.92,0:04:08.48,Default,,0000,0000,0000,,to becoming almost its final value,\Nit's called the forward turn on voltage.
Dialogue: 0,0:04:08.48,0:04:09.96,Default,,0000,0000,0000,,And right here for the red one,
Dialogue: 0,0:04:09.96,0:04:15.23,Default,,0000,0000,0000,,you can see the forward turn on\Nvoltage for a red LED is about 1 volt.
Dialogue: 0,0:04:15.23,0:04:18.62,Default,,0000,0000,0000,,The turn on voltage for\Na white LED would be a little bit higher.
Dialogue: 0,0:04:21.41,0:04:25.14,Default,,0000,0000,0000,,Now let's go back to our idea of\Nthe open circuit and the short circuit.
Dialogue: 0,0:04:25.14,0:04:27.36,Default,,0000,0000,0000,,If I have an open circuit,\Nmy current is 0.
Dialogue: 0,0:04:27.36,0:04:31.92,Default,,0000,0000,0000,,My circuit may not work, but\Nat least it's not gonna run away with me.
Dialogue: 0,0:04:31.92,0:04:35.56,Default,,0000,0000,0000,,My short circuit, on the other hand,\Nhas a very small resistance but
Dialogue: 0,0:04:35.56,0:04:37.32,Default,,0000,0000,0000,,extremely high current.
Dialogue: 0,0:04:37.32,0:04:39.16,Default,,0000,0000,0000,,That's what can actually\Ndo you some damage.
Dialogue: 0,0:04:41.48,0:04:45.36,Default,,0000,0000,0000,,A fuse or a circuit breaker is what's\Nintended to keep the current from running
Dialogue: 0,0:04:45.36,0:04:45.95,Default,,0000,0000,0000,,away with you.
Dialogue: 0,0:04:45.95,0:04:46.73,Default,,0000,0000,0000,,If the current was trying\Nto go to infinity, but
Dialogue: 0,0:04:46.73,0:04:52.07,Default,,0000,0000,0000,,we had a 10-amp circuit breaker in line\Nwith that, the circuit breaker would
Dialogue: 0,0:04:53.47,0:04:57.68,Default,,0000,0000,0000,,trip when the current got to 10 amps and\Nit would shut the circuit off.
Dialogue: 0,0:04:57.68,0:05:01.04,Default,,0000,0000,0000,,A circuit breaker is a type of switch.
Dialogue: 0,0:05:01.04,0:05:03.60,Default,,0000,0000,0000,,There's several other types of switches.
Dialogue: 0,0:05:03.60,0:05:06.65,Default,,0000,0000,0000,,The most common that we use when\Nwe do our designs are single pole,
Dialogue: 0,0:05:06.65,0:05:08.16,Default,,0000,0000,0000,,single throw switches.
Dialogue: 0,0:05:08.16,0:05:12.14,Default,,0000,0000,0000,,That's just a switch that you just\Nturn on, turn off, turn on, turn off.
Dialogue: 0,0:05:12.14,0:05:15.61,Default,,0000,0000,0000,,The other is a single pole double throw,\Nwhere you turn on here or
Dialogue: 0,0:05:15.61,0:05:19.81,Default,,0000,0000,0000,,you turn on there, turn on here, turn on\Nthere, and there are many others as well.
Dialogue: 0,0:05:19.81,0:05:23.03,Default,,0000,0000,0000,,I put a link on the website, and I thought\Nit was pretty interesting for you to see
Dialogue: 0,0:05:23.03,0:05:26.27,Default,,0000,0000,0000,,all the different kinds of switches that\Nyou might be using throughout your career.
Dialogue: 0,0:05:27.73,0:05:32.64,Default,,0000,0000,0000,,One very interesting switch circuit is\Nthe three-way light switch, that's where
Dialogue: 0,0:05:32.64,0:05:37.36,Default,,0000,0000,0000,,you have a voltage source connected on to\Ntwo single pull double throw switches.
Dialogue: 0,0:05:37.36,0:05:39.25,Default,,0000,0000,0000,,These are very common along stairways or
Dialogue: 0,0:05:39.25,0:05:42.31,Default,,0000,0000,0000,,hallways, because you want to\Nable to turn the light on or
Dialogue: 0,0:05:42.31,0:05:47.19,Default,,0000,0000,0000,,off from the top of the stairs as well\Nas from the bottom of the stairs.
Dialogue: 0,0:05:47.19,0:05:49.70,Default,,0000,0000,0000,,Now right here in the circuit,\Nyou'll notice that these two
Dialogue: 0,0:05:49.70,0:05:53.76,Default,,0000,0000,0000,,switches have to be connected by a double\Nset of wires going between them,
Dialogue: 0,0:05:53.76,0:05:58.71,Default,,0000,0000,0000,,and then they're connected on to the lamp\Nor the light bulb along a neutral line.
Dialogue: 0,0:05:58.71,0:06:01.34,Default,,0000,0000,0000,,We often choose to use the light\Nbulb in the neutral line
Dialogue: 0,0:06:01.34,0:06:02.76,Default,,0000,0000,0000,,instead of the power line.
Dialogue: 0,0:06:02.76,0:06:05.88,Default,,0000,0000,0000,,Because in the event that someone\Nwas taking the lightbulb out, and
Dialogue: 0,0:06:05.88,0:06:08.90,Default,,0000,0000,0000,,let's say that they accidentally\Ngot their finger or
Dialogue: 0,0:06:08.90,0:06:12.09,Default,,0000,0000,0000,,maybe a piece of or\Nmaybe a tool across here.
Dialogue: 0,0:06:12.09,0:06:14.67,Default,,0000,0000,0000,,And somehow they managed to\Nshort themselves to a live line,
Dialogue: 0,0:06:14.67,0:06:17.56,Default,,0000,0000,0000,,sorry to the ground.
Dialogue: 0,0:06:17.56,0:06:20.33,Default,,0000,0000,0000,,If we were connected to the neutral,\Nnothing should happen, but
Dialogue: 0,0:06:20.33,0:06:22.61,Default,,0000,0000,0000,,if they were connected to a live line,\Nit should.
Dialogue: 0,0:06:22.61,0:06:25.63,Default,,0000,0000,0000,,So most often, the lamp is put\Non the neutral line for safety.
Dialogue: 0,0:06:27.63,0:06:31.62,Default,,0000,0000,0000,,So in conclusion today, we've talked about\Nvoltage and current sources, open and
Dialogue: 0,0:06:31.62,0:06:33.34,Default,,0000,0000,0000,,short circuits, and switches.
Dialogue: 0,0:06:33.34,0:06:36.31,Default,,0000,0000,0000,,I'd like you to take a minute\Nto try the three-way switch
Dialogue: 0,0:06:36.31,0:06:38.02,Default,,0000,0000,0000,,in your MultiSim simulation.
Dialogue: 0,0:06:38.02,0:06:40.22,Default,,0000,0000,0000,,It's a good chance to get\Nto practice with MultiSim.
Dialogue: 0,0:06:40.22,0:06:44.06,Default,,0000,0000,0000,,And it's fun to see how\Nthe three-way switch works.
Dialogue: 0,0:06:44.06,0:06:46.37,Default,,0000,0000,0000,,Now, let's talk about where\Nthe picture was in the front.
Dialogue: 0,0:06:46.37,0:06:49.05,Default,,0000,0000,0000,,This is the Sunflowers &\NThunderheads picture from
Dialogue: 0,0:06:49.05,0:06:51.86,Default,,0000,0000,0000,,Blackhawk Trail In Payson Canyon, Utah.
Dialogue: 0,0:06:51.86,0:06:53.96,Default,,0000,0000,0000,,See all these yellow\Nsunflowers along here?
Dialogue: 0,0:06:53.96,0:06:55.01,Default,,0000,0000,0000,,It's absolutely amazing.
Dialogue: 0,0:06:55.01,0:06:57.58,Default,,0000,0000,0000,,This is normally the week\Nof the Fourth of July.