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Dialogue: 0,0:00:05.66,0:00:08.40,Default,,0000,0000,0000,,>> In this video, we'll introduce some of
Dialogue: 0,0:00:08.40,0:00:11.44,Default,,0000,0000,0000,,the practical aspects of capacitors and inductors.
Dialogue: 0,0:00:11.44,0:00:13.02,Default,,0000,0000,0000,,As usual in the lab videos,
Dialogue: 0,0:00:13.02,0:00:15.39,Default,,0000,0000,0000,,I'll assume that you're getting the theoretical information about
Dialogue: 0,0:00:15.39,0:00:18.09,Default,,0000,0000,0000,,these devices from the textbook and the lecture videos.
Dialogue: 0,0:00:18.09,0:00:20.48,Default,,0000,0000,0000,,We'll spend our time in this video then,
Dialogue: 0,0:00:20.48,0:00:23.25,Default,,0000,0000,0000,,looking at some physical capacitors and inductors.
Dialogue: 0,0:00:23.25,0:00:26.31,Default,,0000,0000,0000,,Talking a bit about how these devices store energy,
Dialogue: 0,0:00:26.31,0:00:30.38,Default,,0000,0000,0000,,show you how to identify capacitance and inductance values on physical parts,
Dialogue: 0,0:00:30.38,0:00:34.14,Default,,0000,0000,0000,,and show you how to measure capacitances using your DMM.
Dialogue: 0,0:00:34.14,0:00:39.50,Default,,0000,0000,0000,,Sadly, most affordable DMMs do not have an inductance measurement capability.
Dialogue: 0,0:00:39.50,0:00:40.82,Default,,0000,0000,0000,,So, for this course,
Dialogue: 0,0:00:40.82,0:00:45.29,Default,,0000,0000,0000,,we'll just have to believe the nominal inductance values for any inductors that we use.
Dialogue: 0,0:00:45.29,0:00:47.61,Default,,0000,0000,0000,,First, we'll talk about capacitors;
Dialogue: 0,0:00:47.61,0:00:50.03,Default,,0000,0000,0000,,Typical capacitor construction consists of
Dialogue: 0,0:00:50.03,0:00:56.08,Default,,0000,0000,0000,,two conductive elements separated by a non-conductive material, called a dielectric.
Dialogue: 0,0:00:56.08,0:00:59.12,Default,,0000,0000,0000,,The dielectric prevents current flow from one element
Dialogue: 0,0:00:59.12,0:01:02.10,Default,,0000,0000,0000,,to the other and is characterized by its permitivity,
Dialogue: 0,0:01:02.10,0:01:05.28,Default,,0000,0000,0000,,designated by the Greek letter, epsilon.
Dialogue: 0,0:01:05.28,0:01:09.30,Default,,0000,0000,0000,,If we apply a voltage difference between the two plates,
Dialogue: 0,0:01:09.30,0:01:12.17,Default,,0000,0000,0000,,charges will accumulate on the upper and lower plates.
Dialogue: 0,0:01:12.17,0:01:15.84,Default,,0000,0000,0000,,These will create an electric field between the plates.
Dialogue: 0,0:01:15.84,0:01:19.58,Default,,0000,0000,0000,,The capacitor stores energy in this electric field.
Dialogue: 0,0:01:19.58,0:01:24.41,Default,,0000,0000,0000,,Capacitance is a quantity which tells us how much energy a capacitor can store.
Dialogue: 0,0:01:24.41,0:01:27.14,Default,,0000,0000,0000,,For a capacitor consisting of two parallel plates,
Dialogue: 0,0:01:27.14,0:01:30.23,Default,,0000,0000,0000,,like the one we saw in the previous slide, the capacitance is,
Dialogue: 0,0:01:30.23,0:01:33.68,Default,,0000,0000,0000,,A times epsilon over d. Where A,
Dialogue: 0,0:01:33.68,0:01:35.84,Default,,0000,0000,0000,,is the cross-sectional area of the plates,
Dialogue: 0,0:01:35.84,0:01:38.66,Default,,0000,0000,0000,,d is the spacing between the plates,
Dialogue: 0,0:01:38.66,0:01:41.100,Default,,0000,0000,0000,,and epsilon is the permittivity of the dielectric.
Dialogue: 0,0:01:41.100,0:01:46.42,Default,,0000,0000,0000,,So, we can increase the capacitance by increasing the cross-sectional area,
Dialogue: 0,0:01:46.42,0:01:49.91,Default,,0000,0000,0000,,decreasing the spacing, or increasing the permittivity.
Dialogue: 0,0:01:49.91,0:01:53.18,Default,,0000,0000,0000,,Now, let's take a look at a few physical capacitors,
Dialogue: 0,0:01:53.18,0:01:56.58,Default,,0000,0000,0000,,measure their capacitance to get a feeling for these relationships.
Dialogue: 0,0:01:56.58,0:01:59.40,Default,,0000,0000,0000,,This is a variable parallel plate capacitor.
Dialogue: 0,0:01:59.40,0:02:02.36,Default,,0000,0000,0000,,The two plates actually consist of multiple plates each.
Dialogue: 0,0:02:02.36,0:02:05.34,Default,,0000,0000,0000,,So, these fins all create one plate,
Dialogue: 0,0:02:05.34,0:02:06.99,Default,,0000,0000,0000,,they're all electrically connected.
Dialogue: 0,0:02:06.99,0:02:09.59,Default,,0000,0000,0000,,The other plate is created by these fins.
Dialogue: 0,0:02:09.59,0:02:12.86,Default,,0000,0000,0000,,The two sets of fins are separated by air gaps between them,
Dialogue: 0,0:02:12.86,0:02:14.92,Default,,0000,0000,0000,,so the dielectric is simply air.
Dialogue: 0,0:02:14.92,0:02:17.66,Default,,0000,0000,0000,,If I turn the knob on the side of the capacitor,
Dialogue: 0,0:02:17.66,0:02:20.60,Default,,0000,0000,0000,,I can increase or decrease the capacitance,
Dialogue: 0,0:02:20.60,0:02:24.54,Default,,0000,0000,0000,,by increasing or decreasing the area of overlap of the conductors.
Dialogue: 0,0:02:24.54,0:02:26.81,Default,,0000,0000,0000,,Let's measure the capacitance and verify that,
Dialogue: 0,0:02:26.81,0:02:28.94,Default,,0000,0000,0000,,that's what actually happens.
Dialogue: 0,0:02:28.94,0:02:31.70,Default,,0000,0000,0000,,To measure capacitance using my DMM,
Dialogue: 0,0:02:31.70,0:02:35.42,Default,,0000,0000,0000,,I plug the leads into the COM and Volt/Ohm ports.
Dialogue: 0,0:02:35.42,0:02:40.05,Default,,0000,0000,0000,,I also connect the leads to the two terminals of the capacitor.
Dialogue: 0,0:02:40.58,0:02:43.91,Default,,0000,0000,0000,,To measure capacitance, I turn my knobs so that
Dialogue: 0,0:02:43.91,0:02:47.10,Default,,0000,0000,0000,,the indicator lines up with the little capacitor symbol.
Dialogue: 0,0:02:47.10,0:02:50.45,Default,,0000,0000,0000,,Currently, there's little or no overlapping area between
Dialogue: 0,0:02:50.45,0:02:53.87,Default,,0000,0000,0000,,these fins and I get about 0.1 nanofarads.
Dialogue: 0,0:02:53.87,0:02:55.40,Default,,0000,0000,0000,,By turning the knob,
Dialogue: 0,0:02:55.40,0:02:59.44,Default,,0000,0000,0000,,I can increase the overlapping area and increase the capacitance.
Dialogue: 0,0:02:59.44,0:03:01.86,Default,,0000,0000,0000,,Now, it's at about 0.4 nanofarads.
Dialogue: 0,0:03:01.86,0:03:05.48,Default,,0000,0000,0000,,If the fins are entirely overlapped,
Dialogue: 0,0:03:05.48,0:03:08.47,Default,,0000,0000,0000,,I get about 0.7 nanofarads.
Dialogue: 0,0:03:08.47,0:03:12.06,Default,,0000,0000,0000,,Now, let's take a look at a very simple homemade capacitor.
Dialogue: 0,0:03:12.06,0:03:16.01,Default,,0000,0000,0000,,My capacitor consists of two wires which are approximately parallel.
Dialogue: 0,0:03:16.01,0:03:21.30,Default,,0000,0000,0000,,They make two conductive elements with a dielectric between them which is currently air.
Dialogue: 0,0:03:21.30,0:03:25.50,Default,,0000,0000,0000,,I can use this property to measure water level.
Dialogue: 0,0:03:25.50,0:03:27.80,Default,,0000,0000,0000,,If I change the permitivity between these,
Dialogue: 0,0:03:27.80,0:03:29.44,Default,,0000,0000,0000,,it'll change the capacitance.
Dialogue: 0,0:03:29.44,0:03:33.90,Default,,0000,0000,0000,,If I insert my wires into this tube of water,
Dialogue: 0,0:03:33.90,0:03:36.96,Default,,0000,0000,0000,,then when I change the water level,
Dialogue: 0,0:03:36.96,0:03:40.12,Default,,0000,0000,0000,,I will also change the capacitance between these wires.
Dialogue: 0,0:03:40.12,0:03:41.57,Default,,0000,0000,0000,,Let's connect our DMM,
Dialogue: 0,0:03:41.57,0:03:43.96,Default,,0000,0000,0000,,change the water level and see how it works.
Dialogue: 0,0:03:43.96,0:03:46.70,Default,,0000,0000,0000,,Now, when the water level is low,
Dialogue: 0,0:03:46.70,0:03:50.16,Default,,0000,0000,0000,,our capacitance is about a half a nanofarad.
Dialogue: 0,0:03:50.16,0:03:51.74,Default,,0000,0000,0000,,Adding some water to this,
Dialogue: 0,0:03:51.74,0:03:56.85,Default,,0000,0000,0000,,increases the water level and should cause the capacitance to go up.
Dialogue: 0,0:04:03.17,0:04:08.18,Default,,0000,0000,0000,,Now, let's look at some typical capacitors which we'll use to create electric circuits.
Dialogue: 0,0:04:08.18,0:04:09.66,Default,,0000,0000,0000,,The capacitors I'll show you,
Dialogue: 0,0:04:09.66,0:04:11.84,Default,,0000,0000,0000,,are from the digital analog parts kit.
Dialogue: 0,0:04:11.84,0:04:15.10,Default,,0000,0000,0000,,The general principles are applicable to most capacitors.
Dialogue: 0,0:04:15.10,0:04:17.60,Default,,0000,0000,0000,,Capacitors are generally described by the type of
Dialogue: 0,0:04:17.60,0:04:20.20,Default,,0000,0000,0000,,dielectric material and their overall construction.
Dialogue: 0,0:04:20.20,0:04:22.44,Default,,0000,0000,0000,,Most of the capacitors in our parts kit
Dialogue: 0,0:04:22.44,0:04:24.34,Default,,0000,0000,0000,,are disc-shaped, like this one.
Dialogue: 0,0:04:24.34,0:04:26.15,Default,,0000,0000,0000,,On these types of capacitors,
Dialogue: 0,0:04:26.15,0:04:30.77,Default,,0000,0000,0000,,the nominal capacitance is encoded as three numbers printed on the capacitor.
Dialogue: 0,0:04:30.77,0:04:35.86,Default,,0000,0000,0000,,These numbers provide a capacitance in picofarads in exponential notation.
Dialogue: 0,0:04:35.86,0:04:38.06,Default,,0000,0000,0000,,The first two numbers are the mantissa of
Dialogue: 0,0:04:38.06,0:04:40.61,Default,,0000,0000,0000,,the number and the third number is the exponent.
Dialogue: 0,0:04:40.61,0:04:45.31,Default,,0000,0000,0000,,For example, this capacitance has the digits 103 printed on it.
Dialogue: 0,0:04:45.31,0:04:50.08,Default,,0000,0000,0000,,This means that its capacitance is 10 times 10 to the third picofarads.
Dialogue: 0,0:04:50.08,0:04:53.52,Default,,0000,0000,0000,,A picofarad is one times 10 to the minus 12 farads.
Dialogue: 0,0:04:53.52,0:05:00.40,Default,,0000,0000,0000,,Therefore, the capacitance of this capacitor is 10 times 10 to the third picofarads,
Dialogue: 0,0:05:00.40,0:05:02.99,Default,,0000,0000,0000,,which is times 10 to the minus 12,
Dialogue: 0,0:05:02.99,0:05:10.78,Default,,0000,0000,0000,,which is equal to 10 times 10 to the minus 9, or 10 nanofarads.
Dialogue: 0,0:05:10.78,0:05:15.44,Default,,0000,0000,0000,,Our actual measured capacitance is about 11 and a half nanofarads.
Dialogue: 0,0:05:15.44,0:05:18.59,Default,,0000,0000,0000,,Electrolytic capacitors are also fairly common.
Dialogue: 0,0:05:18.59,0:05:23.08,Default,,0000,0000,0000,,In electrolytic capacitors, one or both of the conductive plates are not metallic.
Dialogue: 0,0:05:23.08,0:05:27.30,Default,,0000,0000,0000,,These capacitors tend to have a relatively high capacitance for their size.
Dialogue: 0,0:05:27.30,0:05:33.10,Default,,0000,0000,0000,,The electrolytic capacitors in your parts kits are can-shaped rather than disc-shaped.
Dialogue: 0,0:05:33.10,0:05:35.18,Default,,0000,0000,0000,,Electrolytic capacitors are polarized,
Dialogue: 0,0:05:35.18,0:05:37.34,Default,,0000,0000,0000,,that means they don't really work the same way if you
Dialogue: 0,0:05:37.34,0:05:39.76,Default,,0000,0000,0000,,switch the polarity of the voltage at their terminals.
Dialogue: 0,0:05:39.76,0:05:43.80,Default,,0000,0000,0000,,The polarity is indicated by the length of the leads on the capacitor.
Dialogue: 0,0:05:43.80,0:05:47.78,Default,,0000,0000,0000,,The anode has a longer wire than the cathode.
Dialogue: 0,0:05:47.78,0:05:52.66,Default,,0000,0000,0000,,It is intended that the anode always be at a higher voltage than the cathode.
Dialogue: 0,0:05:52.66,0:05:54.20,Default,,0000,0000,0000,,If you reversed the polarity,
Dialogue: 0,0:05:54.20,0:05:56.39,Default,,0000,0000,0000,,the capacitor properties will be different.
Dialogue: 0,0:05:56.39,0:05:58.58,Default,,0000,0000,0000,,In fact, if you apply a voltage in which
Dialogue: 0,0:05:58.58,0:06:00.95,Default,,0000,0000,0000,,the cathode is at a higher voltage than the anode,
Dialogue: 0,0:06:00.95,0:06:02.70,Default,,0000,0000,0000,,the capacitor can explode.
Dialogue: 0,0:06:02.70,0:06:04.12,Default,,0000,0000,0000,,If you do this, by the way,
Dialogue: 0,0:06:04.12,0:06:06.10,Default,,0000,0000,0000,,I recommend that you wear eye protection.
Dialogue: 0,0:06:06.10,0:06:08.36,Default,,0000,0000,0000,,I've personally never blown up a capacitor by
Dialogue: 0,0:06:08.36,0:06:11.32,Default,,0000,0000,0000,,reversing its polarity, but there's a first time for everything.
Dialogue: 0,0:06:11.32,0:06:13.58,Default,,0000,0000,0000,,The electrolytic capacitors in our kit,
Dialogue: 0,0:06:13.58,0:06:15.83,Default,,0000,0000,0000,,are physically large enough so that the capacitance is
Dialogue: 0,0:06:15.83,0:06:19.18,Default,,0000,0000,0000,,printed directly on the side of the capacitor.
Dialogue: 0,0:06:19.18,0:06:21.38,Default,,0000,0000,0000,,This capacitor, for example,
Dialogue: 0,0:06:21.38,0:06:24.46,Default,,0000,0000,0000,,is nominally 220 microfarads.
Dialogue: 0,0:06:24.46,0:06:28.40,Default,,0000,0000,0000,,The printing on the side of the capacitor also provides additional information.
Dialogue: 0,0:06:28.40,0:06:32.03,Default,,0000,0000,0000,,The cathode is indicated by a white stripe with a minus sign on
Dialogue: 0,0:06:32.03,0:06:36.06,Default,,0000,0000,0000,,it and the maximum allowable safe voltage is also printed out on the side.
Dialogue: 0,0:06:36.06,0:06:39.29,Default,,0000,0000,0000,,This capacitor's rated voltage is 10 volts.
Dialogue: 0,0:06:39.29,0:06:41.72,Default,,0000,0000,0000,,Now, let's talk a bit about inductors.
Dialogue: 0,0:06:41.72,0:06:44.90,Default,,0000,0000,0000,,Inductors like capacitors store electrical energy.
Dialogue: 0,0:06:44.90,0:06:49.08,Default,,0000,0000,0000,,Unlike capacitors, inductors store energy in a magnetic field.
Dialogue: 0,0:06:49.08,0:06:54.60,Default,,0000,0000,0000,,Typical inductors are constructed by winding a conductive wire around a central core.
Dialogue: 0,0:06:54.60,0:06:56.52,Default,,0000,0000,0000,,When current runs through the coil,
Dialogue: 0,0:06:56.52,0:06:58.52,Default,,0000,0000,0000,,a magnetic field is created.
Dialogue: 0,0:06:58.52,0:07:01.19,Default,,0000,0000,0000,,The inductance of the inductor is indicative
Dialogue: 0,0:07:01.19,0:07:03.92,Default,,0000,0000,0000,,of the amount of energy that can be stored by the inductor.
Dialogue: 0,0:07:03.92,0:07:06.98,Default,,0000,0000,0000,,The inductance is typically related to the number of turns
Dialogue: 0,0:07:06.98,0:07:10.16,Default,,0000,0000,0000,,the coil takes around the central core and the core material.
Dialogue: 0,0:07:10.16,0:07:14.58,Default,,0000,0000,0000,,Ferrite core materials typically result in relatively high inductance.
Dialogue: 0,0:07:14.58,0:07:16.76,Default,,0000,0000,0000,,Here's a very simple homemade inductor,
Dialogue: 0,0:07:16.76,0:07:19.20,Default,,0000,0000,0000,,I've simply wrapped wire around a carriage bolt.
Dialogue: 0,0:07:19.20,0:07:21.44,Default,,0000,0000,0000,,If I connect a voltage source to the wire,
Dialogue: 0,0:07:21.44,0:07:25.48,Default,,0000,0000,0000,,current will flow through the wire and a magnetic field will be created.
Dialogue: 0,0:07:25.48,0:07:28.34,Default,,0000,0000,0000,,To create a fairly large magnetic field,
Dialogue: 0,0:07:28.34,0:07:29.64,Default,,0000,0000,0000,,I'll need a high current.
Dialogue: 0,0:07:29.64,0:07:32.48,Default,,0000,0000,0000,,So, I'll use the six-volt batteries as my power source.
Dialogue: 0,0:07:32.48,0:07:35.00,Default,,0000,0000,0000,,I know I have a magnetic field because I can pick up
Dialogue: 0,0:07:35.00,0:07:38.34,Default,,0000,0000,0000,,screws with my newly created electromagnet.
Dialogue: 0,0:07:38.34,0:07:41.64,Default,,0000,0000,0000,,Inductors come in a wide range of shapes and sizes.
Dialogue: 0,0:07:41.64,0:07:45.74,Default,,0000,0000,0000,,This is a large high current inductor, about 120 millihenries.
Dialogue: 0,0:07:45.74,0:07:48.50,Default,,0000,0000,0000,,The analog parts kit contains two inductors;
Dialogue: 0,0:07:48.50,0:07:51.72,Default,,0000,0000,0000,,a one millihenry inductor and a one microhenry inductor.
Dialogue: 0,0:07:51.72,0:07:55.22,Default,,0000,0000,0000,,The millihenry inductor is encoded with the numerals 102 on
Dialogue: 0,0:07:55.22,0:07:59.30,Default,,0000,0000,0000,,the side, and the microhenry inductor has the numerals 1R0.
Dialogue: 0,0:07:59.30,0:08:02.67,Default,,0000,0000,0000,,These are both ferrite core inductors.