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Dialogue: 0,0:00:02.39,0:00:04.37,Default,,0000,0000,0000,,Welcome to Introduction to Electrical and
Dialogue: 0,0:00:04.37,0:00:06.49,Default,,0000,0000,0000,,Computer Engineering at\Nthe University of Utah.
Dialogue: 0,0:00:06.49,0:00:11.53,Default,,0000,0000,0000,,I am Dr. Cynthia Furse, and today,\Nwe'll be talking about voltage and power.
Dialogue: 0,0:00:11.53,0:00:14.48,Default,,0000,0000,0000,,If you have ever wanted\Nto live off the grid, or
Dialogue: 0,0:00:14.48,0:00:18.56,Default,,0000,0000,0000,,if you need an internet base station in\Na remote area, or perhaps you just want to
Dialogue: 0,0:00:18.56,0:00:22.09,Default,,0000,0000,0000,,be able to charge up the batteries\Non your RV, this lecture is for you.
Dialogue: 0,0:00:23.55,0:00:25.46,Default,,0000,0000,0000,,We're going to talk about what is voltage,
Dialogue: 0,0:00:25.46,0:00:28.94,Default,,0000,0000,0000,,how do you measure it,\Nwhat's the polarity, ground, what's power,
Dialogue: 0,0:00:28.94,0:00:32.22,Default,,0000,0000,0000,,what's energy, and then let's get real\Nwith some interesting applications.
Dialogue: 0,0:00:33.47,0:00:36.96,Default,,0000,0000,0000,,Voltage is the energy that's required\Nto move one unit of negative charge,
Dialogue: 0,0:00:36.96,0:00:40.29,Default,,0000,0000,0000,,e minus, to point a to point b.
Dialogue: 0,0:00:40.29,0:00:44.12,Default,,0000,0000,0000,,Another way to think of this is it's\Nthe same energy that's required to lift
Dialogue: 0,0:00:44.12,0:00:48.29,Default,,0000,0000,0000,,one unit of positive charge\Ne from point b to point a.
Dialogue: 0,0:00:48.29,0:00:50.02,Default,,0000,0000,0000,,That's the way I like to think about it.
Dialogue: 0,0:00:50.02,0:00:51.96,Default,,0000,0000,0000,,Voltage is equal to potential.
Dialogue: 0,0:00:51.96,0:00:54.75,Default,,0000,0000,0000,,Think of the voltage as\Na stack of positive charges
Dialogue: 0,0:00:54.75,0:00:56.65,Default,,0000,0000,0000,,at the top of a hill at point a.
Dialogue: 0,0:00:56.65,0:00:58.08,Default,,0000,0000,0000,,This has potential energy.
Dialogue: 0,0:00:59.66,0:01:03.09,Default,,0000,0000,0000,,Voltages are potential differences\Nmeasured between two points.
Dialogue: 0,0:01:03.09,0:01:07.71,Default,,0000,0000,0000,,You can see the voltmeter here who we've\Nconnected the positive red lead onto a and
Dialogue: 0,0:01:07.71,0:01:11.60,Default,,0000,0000,0000,,the common or negative ground lead onto b.
Dialogue: 0,0:01:11.60,0:01:17.38,Default,,0000,0000,0000,,V from point a to point b, or\NVab, this include the 1.5 volts.
Dialogue: 0,0:01:17.38,0:01:20.63,Default,,0000,0000,0000,,That means that Va is 1.5\Nvolts higher than Vb.
Dialogue: 0,0:01:23.16,0:01:24.46,Default,,0000,0000,0000,,Voltage has polarity.
Dialogue: 0,0:01:24.46,0:01:26.05,Default,,0000,0000,0000,,What if I switch my leads?
Dialogue: 0,0:01:26.05,0:01:30.57,Default,,0000,0000,0000,,What if I measure with a red lead at\Npoint b and a negative lead at point a?
Dialogue: 0,0:01:30.57,0:01:35.22,Default,,0000,0000,0000,,Then Vba will be read on\Nthe volt meter as -1.5 volts.
Dialogue: 0,0:01:35.22,0:01:39.80,Default,,0000,0000,0000,,That means that Vb is\N1.5 volts lower than Va.
Dialogue: 0,0:01:39.80,0:01:44.24,Default,,0000,0000,0000,,You could stop for a minute, if you like,\Nand use Multisim to be able to experiment
Dialogue: 0,0:01:44.24,0:01:47.59,Default,,0000,0000,0000,,with your voltage and your voltmeter\Nto be able to see this happen.
Dialogue: 0,0:01:49.59,0:01:52.13,Default,,0000,0000,0000,,Voltage is always measured\Nrelative to a ground.
Dialogue: 0,0:01:52.13,0:01:54.68,Default,,0000,0000,0000,,We also call that the reference or\Nthe neutral.
Dialogue: 0,0:01:54.68,0:01:58.95,Default,,0000,0000,0000,,Here are two cards that show you what\Nsymbols we might use for ground.
Dialogue: 0,0:01:58.95,0:02:02.20,Default,,0000,0000,0000,,We always define the voltage of\Nthe ground as being 0 volts.
Dialogue: 0,0:02:04.10,0:02:06.54,Default,,0000,0000,0000,,Here's an example of\Na very simple circuit.
Dialogue: 0,0:02:06.54,0:02:07.60,Default,,0000,0000,0000,,This is where we have a battery.
Dialogue: 0,0:02:07.60,0:02:09.84,Default,,0000,0000,0000,,It's connected onto two resistors.
Dialogue: 0,0:02:09.84,0:02:15.16,Default,,0000,0000,0000,,And we might be interested in knowing,\Nwhat is Vc in-between these two resistors?
Dialogue: 0,0:02:15.16,0:02:18.98,Default,,0000,0000,0000,,Well, we can tell one thing\Nabout this particular picture.
Dialogue: 0,0:02:18.98,0:02:24.00,Default,,0000,0000,0000,,We know that Vab is 1.5 volts\Nbecause I bought a 1.5 volt battery.
Dialogue: 0,0:02:24.00,0:02:28.14,Default,,0000,0000,0000,,But without having a ground,\NI can't tell you exactly what Vc is.
Dialogue: 0,0:02:28.14,0:02:32.11,Default,,0000,0000,0000,,So let's define the ground at\Na place that's convenient to us.
Dialogue: 0,0:02:32.11,0:02:35.57,Default,,0000,0000,0000,,For me, the most convenient place\Nis at the bottom of the battery, so
Dialogue: 0,0:02:35.57,0:02:38.45,Default,,0000,0000,0000,,I'm going to install my ground\Nright here at this point.
Dialogue: 0,0:02:38.45,0:02:42.57,Default,,0000,0000,0000,,Then I can say, what's Va,\Nwhat's Vb, and what's Vc?
Dialogue: 0,0:02:42.57,0:02:45.33,Default,,0000,0000,0000,,Let's start with Vb, that's the easiest.
Dialogue: 0,0:02:45.33,0:02:46.49,Default,,0000,0000,0000,,Okay, check this out.
Dialogue: 0,0:02:46.49,0:02:52.05,Default,,0000,0000,0000,,Vb is directly connected onto the ground,\Nso I know that Vb is 0 volts.
Dialogue: 0,0:02:52.05,0:02:53.70,Default,,0000,0000,0000,,That's my definition.
Dialogue: 0,0:02:53.70,0:02:57.10,Default,,0000,0000,0000,,I'm gonna use three lines to\Nsay Vb is defined as zero
Dialogue: 0,0:02:57.10,0:02:59.17,Default,,0000,0000,0000,,because that's where I put my ground.
Dialogue: 0,0:02:59.17,0:03:00.71,Default,,0000,0000,0000,,Now, what about Va?
Dialogue: 0,0:03:00.71,0:03:06.14,Default,,0000,0000,0000,,Remember that Va is 1.5 volts above Vb,
Dialogue: 0,0:03:06.14,0:03:10.52,Default,,0000,0000,0000,,Vb is zero, so Va is 1.5 volts.
Dialogue: 0,0:03:10.52,0:03:12.35,Default,,0000,0000,0000,,Now, what about Vc?
Dialogue: 0,0:03:12.35,0:03:15.38,Default,,0000,0000,0000,,We can see that these\Ntwo resistors are equal.
Dialogue: 0,0:03:15.38,0:03:18.97,Default,,0000,0000,0000,,That means that the voltage is going\Nto be evenly split between them.
Dialogue: 0,0:03:18.97,0:03:24.91,Default,,0000,0000,0000,,The voltage between this point right here\Nand the bottom, which is 0, is 1.5 volts.
Dialogue: 0,0:03:24.91,0:03:29.23,Default,,0000,0000,0000,,So Vc is going to be halfway\Nin between 1.5 volts and 0,
Dialogue: 0,0:03:29.23,0:03:33.16,Default,,0000,0000,0000,,where it's going to be 0.75 volts.
Dialogue: 0,0:03:35.20,0:03:38.31,Default,,0000,0000,0000,,Now, this particular definition of Va,\NVb, and
Dialogue: 0,0:03:38.31,0:03:42.00,Default,,0000,0000,0000,,Vc is totally dependent on\Nwhere I placed my ground.
Dialogue: 0,0:03:42.00,0:03:43.98,Default,,0000,0000,0000,,Let me show you what I mean.
Dialogue: 0,0:03:43.98,0:03:45.80,Default,,0000,0000,0000,,Let's go choose a different ground point.
Dialogue: 0,0:03:47.36,0:03:51.19,Default,,0000,0000,0000,,This time, let's put our ground right\Nhere in-between the two resistors.
Dialogue: 0,0:03:51.19,0:03:53.24,Default,,0000,0000,0000,,It's legal, we can go ahead and do that.
Dialogue: 0,0:03:53.24,0:03:56.26,Default,,0000,0000,0000,,It may not be quite as convenient,\Nbut let's see what happens.
Dialogue: 0,0:03:56.26,0:03:58.41,Default,,0000,0000,0000,,Okay, Vc is at the point of the ground.
Dialogue: 0,0:03:58.41,0:04:04.71,Default,,0000,0000,0000,,So remember, the ground defines our\Nvoltage as being 0, so Vc is equal to 0.
Dialogue: 0,0:04:04.71,0:04:07.51,Default,,0000,0000,0000,,Now, what about Va and Vb?
Dialogue: 0,0:04:07.51,0:04:11.58,Default,,0000,0000,0000,,Well, we know that Va is\N1.5 volts higher than Vb.
Dialogue: 0,0:04:11.58,0:04:14.67,Default,,0000,0000,0000,,And how about its relationship to Vc?
Dialogue: 0,0:04:14.67,0:04:18.86,Default,,0000,0000,0000,,Well, because we originally\Nsplit the voltage here,
Dialogue: 0,0:04:18.86,0:04:23.87,Default,,0000,0000,0000,,we're going to still be splitting\Nthe voltage, so we can see that
Dialogue: 0,0:04:23.87,0:04:30.26,Default,,0000,0000,0000,,Va is going to be 0.75 volts higher than\NVc, so Va is going to be 0.75 volts.
Dialogue: 0,0:04:30.26,0:04:32.13,Default,,0000,0000,0000,,All right, what about Vb?
Dialogue: 0,0:04:32.13,0:04:37.23,Default,,0000,0000,0000,,Well, that's going to be\N0.75 volts lower than Vc,
Dialogue: 0,0:04:37.23,0:04:40.96,Default,,0000,0000,0000,,so that's going to be -0.75 volts.
Dialogue: 0,0:04:40.96,0:04:43.87,Default,,0000,0000,0000,,Let's kinda check ourselves.
Dialogue: 0,0:04:43.87,0:04:48.32,Default,,0000,0000,0000,,We know that Vab has to be 1.5 volts,\Nis that going to be true?
Dialogue: 0,0:04:48.32,0:04:53.14,Default,,0000,0000,0000,,Va is 0.75 volts, Vb is -0.75 volts, so
Dialogue: 0,0:04:53.14,0:04:57.52,Default,,0000,0000,0000,,absolutely, we got our 1.5 volts.
Dialogue: 0,0:04:57.52,0:05:01.10,Default,,0000,0000,0000,,Now, notice that the relative voltages in\Nthis circuit are the same as they were
Dialogue: 0,0:05:01.10,0:05:03.70,Default,,0000,0000,0000,,before when we had our\Nground at the bottom, but
Dialogue: 0,0:05:03.70,0:05:07.18,Default,,0000,0000,0000,,the absolute values of these\Nvoltages are different.
Dialogue: 0,0:05:07.18,0:05:08.29,Default,,0000,0000,0000,,Does it matter?
Dialogue: 0,0:05:08.29,0:05:09.97,Default,,0000,0000,0000,,The answer is no.
Dialogue: 0,0:05:09.97,0:05:14.52,Default,,0000,0000,0000,,Everything in my circuit can be relative\Nto the ground at any location, and
Dialogue: 0,0:05:14.52,0:05:16.81,Default,,0000,0000,0000,,I can do my calculations accordingly.
Dialogue: 0,0:05:16.81,0:05:19.49,Default,,0000,0000,0000,,So it doesn't matter where I put my ground
Dialogue: 0,0:05:19.49,0:05:23.70,Default,,0000,0000,0000,,except that I'm most often going to\Nchoose it for my calculation convenience.
Dialogue: 0,0:05:24.98,0:05:26.55,Default,,0000,0000,0000,,Okay, let's go on to the next idea.
Dialogue: 0,0:05:28.10,0:05:29.94,Default,,0000,0000,0000,,Let's talk about some real stuff.
Dialogue: 0,0:05:29.94,0:05:33.29,Default,,0000,0000,0000,,So what's a really big voltage, and\Nwhat's a really little voltage?
Dialogue: 0,0:05:33.29,0:05:36.58,Default,,0000,0000,0000,,Let's have some ideas in mind so\Nthat when we do our calculations,
Dialogue: 0,0:05:36.58,0:05:40.69,Default,,0000,0000,0000,,our math, we have an idea if we're\Ngetting something that's reasonable.
Dialogue: 0,0:05:40.69,0:05:43.75,Default,,0000,0000,0000,,The biggest voltage that I could\Nfind in nature is lightning.
Dialogue: 0,0:05:43.75,0:05:46.93,Default,,0000,0000,0000,,It's not uncommon for\Nlightning to have 1 billion volts.
Dialogue: 0,0:05:46.93,0:05:50.77,Default,,0000,0000,0000,,That's one times tenth to the ninth,\Nthat is really big voltage.
Dialogue: 0,0:05:50.77,0:05:54.28,Default,,0000,0000,0000,,There's some interesting information on\Nlightning in the reference material at
Dialogue: 0,0:05:54.28,0:05:56.34,Default,,0000,0000,0000,,the end of this lecture.
Dialogue: 0,0:05:56.34,0:05:59.05,Default,,0000,0000,0000,,High voltage lines also\Nhave large voltage.
Dialogue: 0,0:05:59.05,0:06:02.75,Default,,0000,0000,0000,,High voltage lines are often 110\Nkilovolts or higher, and indeed,
Dialogue: 0,0:06:02.75,0:06:05.31,Default,,0000,0000,0000,,they are considered high voltage.
Dialogue: 0,0:06:05.31,0:06:09.53,Default,,0000,0000,0000,,Your house, your residential\Nconstruction has 240 volts for
Dialogue: 0,0:06:09.53,0:06:13.75,Default,,0000,0000,0000,,your largest appliances and\N120 for most of your general use.
Dialogue: 0,0:06:15.26,0:06:17.55,Default,,0000,0000,0000,,Now, what's a really small voltage?
Dialogue: 0,0:06:17.55,0:06:22.11,Default,,0000,0000,0000,,Neural action potentials, the electric\Npotential that stimulates a single neuron,
Dialogue: 0,0:06:22.11,0:06:23.99,Default,,0000,0000,0000,,is a relatively small voltage.
Dialogue: 0,0:06:23.99,0:06:26.67,Default,,0000,0000,0000,,That's about -55 millivolts.
Dialogue: 0,0:06:26.67,0:06:33.84,Default,,0000,0000,0000,,Your cardiac action potential is about the\Nsame range, that's -100 to +50 millivolts.
Dialogue: 0,0:06:33.84,0:06:37.81,Default,,0000,0000,0000,,A bird sitting on a power line is\Nanother example of a very small voltage.
Dialogue: 0,0:06:37.81,0:06:40.39,Default,,0000,0000,0000,,We say the bird can sit on\Nthe line without being shocked
Dialogue: 0,0:06:40.39,0:06:42.54,Default,,0000,0000,0000,,because it has no potential difference.
Dialogue: 0,0:06:42.54,0:06:43.81,Default,,0000,0000,0000,,It's not exactly right.
Dialogue: 0,0:06:43.81,0:06:47.81,Default,,0000,0000,0000,,Has a very small potential difference of\Nabout 10 millivolts between the left and
Dialogue: 0,0:06:47.81,0:06:51.25,Default,,0000,0000,0000,,the right leg, and that is small\Nenough that it doesn't hurt the bird.
Dialogue: 0,0:06:52.52,0:06:56.38,Default,,0000,0000,0000,,There's some very interesting research\Ngoing on at the University of Utah
Dialogue: 0,0:06:56.38,0:07:00.95,Default,,0000,0000,0000,,relative to electrodes and neurons\Nthat you might be very interested in.
Dialogue: 0,0:07:00.95,0:07:06.05,Default,,0000,0000,0000,,The Utah electrode array is a very small\Narray made from silicone that has ten
Dialogue: 0,0:07:06.05,0:07:07.95,Default,,0000,0000,0000,,electrodes by ten electrodes.
Dialogue: 0,0:07:07.95,0:07:09.56,Default,,0000,0000,0000,,Each electrode is like a tiny needle.
Dialogue: 0,0:07:09.56,0:07:14.55,Default,,0000,0000,0000,,It's made from silicon, it is conductive,\Nit's connected to an individual line.
Dialogue: 0,0:07:14.55,0:07:19.05,Default,,0000,0000,0000,,If you look at this big kind of gold line\Nright here, that has 100 little different
Dialogue: 0,0:07:19.05,0:07:23.65,Default,,0000,0000,0000,,lines, about [INAUDIBLE] of hair\Nthat come back to a central system.
Dialogue: 0,0:07:23.65,0:07:28.37,Default,,0000,0000,0000,,This electrode array can be placed in or\Nin contact with any nerve.
Dialogue: 0,0:07:28.37,0:07:32.00,Default,,0000,0000,0000,,For example, it could be stuck\Non the surface of the brain.
Dialogue: 0,0:07:32.00,0:07:34.43,Default,,0000,0000,0000,,This can be used to either\Nreceive from the nerves and
Dialogue: 0,0:07:34.43,0:07:38.31,Default,,0000,0000,0000,,be able to read their signals, or\Nit can be used to stimulate them.
Dialogue: 0,0:07:38.31,0:07:42.42,Default,,0000,0000,0000,,This Utah electrode array is being put\Ninto commercial products to help blind
Dialogue: 0,0:07:42.42,0:07:47.45,Default,,0000,0000,0000,,people see, deaf people hear, and people\Nwho have lost the use of their limbs
Dialogue: 0,0:07:47.45,0:07:53.12,Default,,0000,0000,0000,,to be able to regain that use or to be\Nable to use bionic limbs as a substitute.
Dialogue: 0,0:07:53.12,0:07:55.25,Default,,0000,0000,0000,,Very, very interesting\Nresearch going on right now.
Dialogue: 0,0:07:56.96,0:07:58.69,Default,,0000,0000,0000,,Now let's talk about power.
Dialogue: 0,0:07:58.69,0:08:02.10,Default,,0000,0000,0000,,Power is given in watts,\Nthat is voltage times current.
Dialogue: 0,0:08:02.10,0:08:07.12,Default,,0000,0000,0000,,So watts is volts times amps,\Nso p is equal to VI.
Dialogue: 0,0:08:07.12,0:08:10.19,Default,,0000,0000,0000,,Power is also the time\Nrate of change of energy.
Dialogue: 0,0:08:10.19,0:08:11.89,Default,,0000,0000,0000,,DW is not watts.
Dialogue: 0,0:08:11.89,0:08:14.91,Default,,0000,0000,0000,,DW is energy,\Nas the change of energy per time, and
Dialogue: 0,0:08:14.91,0:08:17.58,Default,,0000,0000,0000,,that would be the power\Nas a function of time.
Dialogue: 0,0:08:19.38,0:08:23.16,Default,,0000,0000,0000,,The passive sign convention tells us\Nif a device is consuming power or
Dialogue: 0,0:08:23.16,0:08:24.50,Default,,0000,0000,0000,,producing power.
Dialogue: 0,0:08:24.50,0:08:27.03,Default,,0000,0000,0000,,Here's how the passive\Nsign convention works.
Dialogue: 0,0:08:27.03,0:08:32.01,Default,,0000,0000,0000,,Define a device, shown here as the dark\Nblue box, and one side of the device is a,
Dialogue: 0,0:08:32.01,0:08:33.27,Default,,0000,0000,0000,,the other side is b.
Dialogue: 0,0:08:33.27,0:08:39.15,Default,,0000,0000,0000,,Vab is the potential across that device,\Nmight be positive, might be negative.
Dialogue: 0,0:08:39.15,0:08:42.78,Default,,0000,0000,0000,,Then define the current going into\Nthe device in the direction shown here,
Dialogue: 0,0:08:42.78,0:08:44.39,Default,,0000,0000,0000,,from plus to minus.
Dialogue: 0,0:08:44.39,0:08:46.78,Default,,0000,0000,0000,,The current is always defined\Nas positive in this way.
Dialogue: 0,0:08:48.85,0:08:50.46,Default,,0000,0000,0000,,Here's an example.
Dialogue: 0,0:08:50.46,0:08:52.01,Default,,0000,0000,0000,,Here's the battery with a resistor.
Dialogue: 0,0:08:52.01,0:08:55.51,Default,,0000,0000,0000,,I've chosen a single resistor\Nhere just for your simplicity.
Dialogue: 0,0:08:55.51,0:09:00.10,Default,,0000,0000,0000,,The current, and we calculated this in\NMultisim before, is the voltage divided by
Dialogue: 0,0:09:00.10,0:09:05.92,Default,,0000,0000,0000,,the resistance, or 1.5 milliamps in\Nthis case if we have a 1.5 volt battery.
Dialogue: 0,0:09:05.92,0:09:07.50,Default,,0000,0000,0000,,Now, let's look over here and
Dialogue: 0,0:09:07.50,0:09:10.72,Default,,0000,0000,0000,,determine what the voltage across\Nthat resistor is going to be.
Dialogue: 0,0:09:10.72,0:09:12.79,Default,,0000,0000,0000,,The voltage is going to be IR.
Dialogue: 0,0:09:12.79,0:09:16.06,Default,,0000,0000,0000,,I is 1.5 milliamps,\Nthe resistance is 1 kiloohms,
Dialogue: 0,0:09:16.06,0:09:19.18,Default,,0000,0000,0000,,so the voltage across that\Nresistor is 1.5 volts.
Dialogue: 0,0:09:20.31,0:09:22.55,Default,,0000,0000,0000,,Now, let's see what\Nhappens with the power.
Dialogue: 0,0:09:22.55,0:09:26.06,Default,,0000,0000,0000,,Let's first calculate the power here\Non the right, for the resistor.
Dialogue: 0,0:09:26.06,0:09:29.78,Default,,0000,0000,0000,,Well, here's our device,\Nthis resistor, and
Dialogue: 0,0:09:29.78,0:09:33.92,Default,,0000,0000,0000,,the voltage across it is 1.5 volts,\Npositive 1.5 volts.
Dialogue: 0,0:09:33.92,0:09:37.70,Default,,0000,0000,0000,,And the current is positive 1.5 milliamps.
Dialogue: 0,0:09:37.70,0:09:44.43,Default,,0000,0000,0000,,So the power is going to be 1.5 volts\Ntimes 1.5 milliamps or 2.25 milliwatts.
Dialogue: 0,0:09:44.43,0:09:48.10,Default,,0000,0000,0000,,Since the power is positive,\Nthe resistor is consuming power.
Dialogue: 0,0:09:48.10,0:09:49.02,Default,,0000,0000,0000,,That is what we expect.
Dialogue: 0,0:09:49.02,0:09:54.51,Default,,0000,0000,0000,,In fact, resistors consume power and\Nconvert it into heat or light energy.
Dialogue: 0,0:09:54.51,0:09:56.29,Default,,0000,0000,0000,,Now, let's come over to this side.
Dialogue: 0,0:09:56.29,0:09:59.52,Default,,0000,0000,0000,,We know intrinsically that\Nthe battery must be producing power.
Dialogue: 0,0:09:59.52,0:10:02.01,Default,,0000,0000,0000,,Let's see if that happens mathematically.
Dialogue: 0,0:10:02.01,0:10:06.09,Default,,0000,0000,0000,,When we're looking at this, we're going\Nto consider this to be our device, and
Dialogue: 0,0:10:06.09,0:10:10.45,Default,,0000,0000,0000,,the current is coming into the device\Nin the positive to negative direction.
Dialogue: 0,0:10:10.45,0:10:14.02,Default,,0000,0000,0000,,The current, in this way,\Nis 1.5 milliamps positive.
Dialogue: 0,0:10:14.02,0:10:18.51,Default,,0000,0000,0000,,The voltage, if we're looking at it in\Nthis direction, from bottom to top, not
Dialogue: 0,0:10:18.51,0:10:24.20,Default,,0000,0000,0000,,from top to bottom, from bottom to top,\Nthe voltage is going to be -1.5 volts.
Dialogue: 0,0:10:24.20,0:10:29.39,Default,,0000,0000,0000,,So the power is equal to -1.5\Nvolts times +1.5 milliamps for
Dialogue: 0,0:10:29.39,0:10:32.58,Default,,0000,0000,0000,,a total of -2.25 milliwatts.
Dialogue: 0,0:10:32.58,0:10:34.44,Default,,0000,0000,0000,,Remember, if the power is negative,
Dialogue: 0,0:10:34.44,0:10:38.78,Default,,0000,0000,0000,,that means that the device is producing\Npower instead of using power.
Dialogue: 0,0:10:38.78,0:10:43.52,Default,,0000,0000,0000,,Another important feature of powers, the\Npower has to be conserved within a system.
Dialogue: 0,0:10:43.52,0:10:46.46,Default,,0000,0000,0000,,There's no place for\Nloose power to be hanging out.
Dialogue: 0,0:10:46.46,0:10:51.30,Default,,0000,0000,0000,,So we can see that our power that's\Nproduced is -2.25 milliwatts, the power
Dialogue: 0,0:10:51.30,0:10:56.57,Default,,0000,0000,0000,,that is used is 2.25 milliwatts, and these\Ntwo things have to be equal and opposite.
Dialogue: 0,0:10:58.54,0:11:00.63,Default,,0000,0000,0000,,Now, let's talk about the energy.
Dialogue: 0,0:11:00.63,0:11:04.07,Default,,0000,0000,0000,,The energy and the picture that we use for
Dialogue: 0,0:11:04.07,0:11:09.33,Default,,0000,0000,0000,,that is W, the variable we use is W,\Nthat's given in Joules or kilowatt hours.
Dialogue: 0,0:11:09.33,0:11:12.82,Default,,0000,0000,0000,,Most of the things that we use to measure\Nin electrical engineering are kilowatt
Dialogue: 0,0:11:12.82,0:11:13.34,Default,,0000,0000,0000,,hours, but
Dialogue: 0,0:11:13.34,0:11:16.79,Default,,0000,0000,0000,,most of the things mechanical engineers\Nwill be talking about will be joules.
Dialogue: 0,0:11:16.79,0:11:24.00,Default,,0000,0000,0000,,They are the same thing.
Dialogue: 0,0:11:24.00,0:11:27.78,Default,,0000,0000,0000,,The energy is the integration\Nover time of the power.
Dialogue: 0,0:11:27.78,0:11:32.28,Default,,0000,0000,0000,,That means that we take the power, and all\Nthe power that we might have used all day,
Dialogue: 0,0:11:32.28,0:11:35.45,Default,,0000,0000,0000,,if t is our day, is going to\Ntell us how much energy we used.
Dialogue: 0,0:11:35.45,0:11:38.90,Default,,0000,0000,0000,,1 joule is equal to 1 watt second, so
Dialogue: 0,0:11:38.90,0:11:42.14,Default,,0000,0000,0000,,let's see what 1 kilowatt\Nhour is equal to.
Dialogue: 0,0:11:42.14,0:11:47.01,Default,,0000,0000,0000,,1 kilowatt hour, and let's balance our\Nunits, I need a watt on the bottom and
Dialogue: 0,0:11:47.01,0:11:49.78,Default,,0000,0000,0000,,an hour on the bottom in\Norder to cancel these out.
Dialogue: 0,0:11:49.78,0:11:52.70,Default,,0000,0000,0000,,1 kilowatt hour times 1\Njoule per watt seconds,
Dialogue: 0,0:11:52.70,0:11:56.32,Default,,0000,0000,0000,,times 60 seconds per minute,\N60 minutes per hour.
Dialogue: 0,0:11:56.32,0:11:59.20,Default,,0000,0000,0000,,My minutes cancel out,\Nmy seconds cancel out.
Dialogue: 0,0:11:59.20,0:12:04.11,Default,,0000,0000,0000,,My watt hours cancel out, leaving me\Nwith Joules and this k over here, so
Dialogue: 0,0:12:04.11,0:12:06.05,Default,,0000,0000,0000,,I get 3600 kilojoules.
Dialogue: 0,0:12:06.05,0:12:09.70,Default,,0000,0000,0000,,1 kWh is 3600 kilojoules.
Dialogue: 0,0:12:11.23,0:12:16.18,Default,,0000,0000,0000,,Now, let's figure out what energy you\Nneed, how much energy do you need?
Dialogue: 0,0:12:16.18,0:12:20.11,Default,,0000,0000,0000,,This is a picture of the Internet base\Nstation on the mountain above my house.
Dialogue: 0,0:12:20.11,0:12:21.84,Default,,0000,0000,0000,,It's a solar-powered base station.
Dialogue: 0,0:12:21.84,0:12:25.14,Default,,0000,0000,0000,,The power is stored in car batteries,\N12 volt batteries.
Dialogue: 0,0:12:25.14,0:12:28.08,Default,,0000,0000,0000,,And then the base station,\Nthat's the little antenna right there,
Dialogue: 0,0:12:28.08,0:12:30.75,Default,,0000,0000,0000,,is a line of site base station\Nover the Park City for
Dialogue: 0,0:12:30.75,0:12:34.12,Default,,0000,0000,0000,,mountain peak to mountain\Npeak several miles away.
Dialogue: 0,0:12:34.12,0:12:37.18,Default,,0000,0000,0000,,In order to figure out how\Nmuch solar panel you need,
Dialogue: 0,0:12:37.18,0:12:40.44,Default,,0000,0000,0000,,you first are going to make your\Ndevice as efficient as possible.
Dialogue: 0,0:12:40.44,0:12:42.36,Default,,0000,0000,0000,,Figure out how many kilowatts you need.
Dialogue: 0,0:12:42.36,0:12:45.97,Default,,0000,0000,0000,,Then you're gong to decide how many\Nhours that needs to be able to run.
Dialogue: 0,0:12:45.97,0:12:48.44,Default,,0000,0000,0000,,Now, when you're considering\Nthe number of hours,
Dialogue: 0,0:12:48.44,0:12:51.100,Default,,0000,0000,0000,,you want to consider how much time you\Ncan actually charge your solar panels,
Dialogue: 0,0:12:51.100,0:12:56.16,Default,,0000,0000,0000,,which obviously is only during the day,\Nand a fact that it's only the good days.
Dialogue: 0,0:12:56.16,0:12:59.89,Default,,0000,0000,0000,,So if you have dark rainy days,\Nyou need to have enough power stored up.
Dialogue: 0,0:12:59.89,0:13:04.32,Default,,0000,0000,0000,,So you take the number of hours,\Nyou multiply the number of appliances in
Dialogue: 0,0:13:04.32,0:13:08.98,Default,,0000,0000,0000,,kilowatts times the number of hours\Nyou plan to use those devices, and
Dialogue: 0,0:13:08.98,0:13:11.25,Default,,0000,0000,0000,,add it up to get kilowatt hours.
Dialogue: 0,0:13:11.25,0:13:16.48,Default,,0000,0000,0000,,Consider the recharge time for\Nnight, dark or snowy days, etc.
Dialogue: 0,0:13:16.48,0:13:19.47,Default,,0000,0000,0000,,I put some interesting links online so\Nthat you could calculate this for
Dialogue: 0,0:13:19.47,0:13:21.69,Default,,0000,0000,0000,,an application of your interest, or
Dialogue: 0,0:13:21.69,0:13:24.95,Default,,0000,0000,0000,,perhaps figure out just how much\Npower you're using in your own home.
Dialogue: 0,0:13:26.83,0:13:30.63,Default,,0000,0000,0000,,So our summary of voltage and power is\Nwe talked about what is voltage and
Dialogue: 0,0:13:30.63,0:13:31.94,Default,,0000,0000,0000,,how you measure it.
Dialogue: 0,0:13:31.94,0:13:36.45,Default,,0000,0000,0000,,It's polarity, the impact of using a\Nground and where you place the ground, and
Dialogue: 0,0:13:36.45,0:13:38.62,Default,,0000,0000,0000,,what is power, and what is energy.
Dialogue: 0,0:13:38.62,0:13:41.11,Default,,0000,0000,0000,,Then we talked about some\Ninteresting real applications.
Dialogue: 0,0:13:42.27,0:13:45.12,Default,,0000,0000,0000,,Now, here is,\Nyou've wondered what is on the front side.
Dialogue: 0,0:13:45.12,0:13:47.93,Default,,0000,0000,0000,,Here's the Solar Powered\NNeighborhood Internet Base Station
Dialogue: 0,0:13:47.93,0:13:49.39,Default,,0000,0000,0000,,at the top of Emigration Canyon.
Dialogue: 0,0:13:50.52,0:13:54.49,Default,,0000,0000,0000,,The view from above, over to Park City,\Nyou can see the mountain top that
Dialogue: 0,0:13:54.49,0:13:58.21,Default,,0000,0000,0000,,it's transmitting to and\Nreceiving from is quite a distance away.
Dialogue: 0,0:13:58.21,0:14:00.24,Default,,0000,0000,0000,,How do you get all that stuff up there,\Nand
Dialogue: 0,0:14:00.24,0:14:03.50,Default,,0000,0000,0000,,why do you care about the number\Nof solar panels and the batteries?
Dialogue: 0,0:14:03.50,0:14:08.73,Default,,0000,0000,0000,,Well, it's 200 pounds of car batteries\Ncarried up by people and by horses.
Dialogue: 0,0:14:08.73,0:14:11.01,Default,,0000,0000,0000,,As well as the base station\Nthat you can see right here,
Dialogue: 0,0:14:11.01,0:14:14.07,Default,,0000,0000,0000,,a couple of the neighbors\Ncarrying that up on a pole.
Dialogue: 0,0:14:14.07,0:14:16.06,Default,,0000,0000,0000,,If you have to carry all of this\Nstuff to the top of the mountain,
Dialogue: 0,0:14:16.06,0:14:20.19,Default,,0000,0000,0000,,you are going to carry as few solar\Npanels and as few batteries as possible.
Dialogue: 0,0:14:21.27,0:14:24.93,Default,,0000,0000,0000,,So now, take a look at your own\Napplications, find something interesting,
Dialogue: 0,0:14:24.93,0:14:29.09,Default,,0000,0000,0000,,and estimate the amount of solar power\Nthat you would need for that application.