[Script Info]
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Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.44,0:00:03.90,Default,,0000,0000,0000,,>> We're going to continue on with\Nour discussion of impedance in
Dialogue: 0,0:00:03.90,0:00:05.79,Default,,0000,0000,0000,,this Phasor Domain analysis of
Dialogue: 0,0:00:05.79,0:00:08.78,Default,,0000,0000,0000,,circuits that are operating\Nthe sinusoidal steady-state.
Dialogue: 0,0:00:08.78,0:00:11.94,Default,,0000,0000,0000,,More particularly, we're going\Nto introduce the concept of
Dialogue: 0,0:00:11.94,0:00:15.27,Default,,0000,0000,0000,,complex impedance where\Nwe'll see that impedance in
Dialogue: 0,0:00:15.27,0:00:18.12,Default,,0000,0000,0000,,general has a real part and
Dialogue: 0,0:00:18.12,0:00:20.52,Default,,0000,0000,0000,,an imaginary part and can\Nbe represented in either
Dialogue: 0,0:00:20.52,0:00:23.36,Default,,0000,0000,0000,,rectangular coordinates\Nor in polar coordinates.
Dialogue: 0,0:00:23.36,0:00:25.98,Default,,0000,0000,0000,,We'll then go on and extend\Nour understanding or
Dialogue: 0,0:00:25.98,0:00:28.95,Default,,0000,0000,0000,,expand our understanding of series and
Dialogue: 0,0:00:28.95,0:00:32.04,Default,,0000,0000,0000,,parallel connections to\Ninclude impedance and
Dialogue: 0,0:00:32.04,0:00:35.79,Default,,0000,0000,0000,,look at how the concept of voltage and\Ncurrent division apply with impedances.
Dialogue: 0,0:00:35.79,0:00:40.48,Default,,0000,0000,0000,,Then, we'll look at Delta to\NWye transformations involving impedances.
Dialogue: 0,0:00:40.48,0:00:43.31,Default,,0000,0000,0000,,So, we've seen that the impedance of
Dialogue: 0,0:00:43.31,0:00:48.76,Default,,0000,0000,0000,,a resistor Z sub R is simply equal\Nto the value of the resistance.
Dialogue: 0,0:00:48.76,0:00:51.04,Default,,0000,0000,0000,,It's a real quantity.
Dialogue: 0,0:00:51.04,0:00:53.82,Default,,0000,0000,0000,,On the other hand, we've\Nseen that the inductor,
Dialogue: 0,0:00:53.82,0:00:57.66,Default,,0000,0000,0000,,impedance of an inductor is\Nequal to j times omega times L,
Dialogue: 0,0:00:57.66,0:01:00.63,Default,,0000,0000,0000,,and it's an imaginary number.
Dialogue: 0,0:01:02.48,0:01:06.88,Default,,0000,0000,0000,,Similarly, Z sub C is equal to negative J
Dialogue: 0,0:01:06.88,0:01:12.14,Default,,0000,0000,0000,,over omega C. Again, an imaginary number.
Dialogue: 0,0:01:12.14,0:01:15.28,Default,,0000,0000,0000,,We observe, and let's reiterate that
Dialogue: 0,0:01:15.28,0:01:18.62,Default,,0000,0000,0000,,the impedance of an inductor\Nis a positive quantity
Dialogue: 0,0:01:18.62,0:01:24.83,Default,,0000,0000,0000,,while the impedance of a capacitor\Nis a negative quantity.
Dialogue: 0,0:01:24.83,0:01:29.60,Default,,0000,0000,0000,,In general, we will talk about Z,
Dialogue: 0,0:01:29.60,0:01:35.82,Default,,0000,0000,0000,,a complex number that will have\Na real part and an imaginary part.
Dialogue: 0,0:01:35.82,0:01:39.78,Default,,0000,0000,0000,,The real part we're going\Nto refer to as resistance,
Dialogue: 0,0:01:40.30,0:01:45.87,Default,,0000,0000,0000,,the imaginary part we're going\Nto refer to as reactance.
Dialogue: 0,0:01:46.79,0:01:53.81,Default,,0000,0000,0000,,Again, a positive reactance refers\Nto an inductive or an impedance,
Dialogue: 0,0:01:53.81,0:01:55.25,Default,,0000,0000,0000,,it has an inductive nature,
Dialogue: 0,0:01:55.25,0:02:00.85,Default,,0000,0000,0000,,and a negative reactance\Nhas a capacity of nature.
Dialogue: 0,0:02:00.85,0:02:04.06,Default,,0000,0000,0000,,Now, we can also talk about Z in
Dialogue: 0,0:02:04.06,0:02:08.85,Default,,0000,0000,0000,,polar coordinates where z then\Ncan also be referred to as,
Dialogue: 0,0:02:08.85,0:02:13.72,Default,,0000,0000,0000,,or Z equals magnitude\Nof Z E to the j theta,
Dialogue: 0,0:02:13.72,0:02:16.68,Default,,0000,0000,0000,,where the magnitude of Z is\Nequal to the square root
Dialogue: 0,0:02:16.68,0:02:21.46,Default,,0000,0000,0000,,of R squared plus X squared,
Dialogue: 0,0:02:21.46,0:02:27.31,Default,,0000,0000,0000,,and theta is equal to the arctangent\Nof the imaginary part,
Dialogue: 0,0:02:27.31,0:02:31.18,Default,,0000,0000,0000,,the reactance divided by the resistance.
Dialogue: 0,0:02:31.18,0:02:37.48,Default,,0000,0000,0000,,For example, if we have a resistor and\Ninductor in series with each other,
Dialogue: 0,0:02:37.48,0:02:40.67,Default,,0000,0000,0000,,the net impedance would be then R plus
Dialogue: 0,0:02:40.67,0:02:44.21,Default,,0000,0000,0000,,J omega L. If you add\Na resistor and a capacitor,
Dialogue: 0,0:02:44.21,0:02:51.05,Default,,0000,0000,0000,,you'd have R minus j times\N1 over omega C squared.
Dialogue: 0,0:02:51.05,0:02:53.06,Default,,0000,0000,0000,,In those instances where you have
Dialogue: 0,0:02:53.06,0:02:55.70,Default,,0000,0000,0000,,both an inductor and\Na capacitor being combined,
Dialogue: 0,0:02:55.70,0:02:59.60,Default,,0000,0000,0000,,the impedance will be pure\Nimaginary and it'll equal J
Dialogue: 0,0:02:59.60,0:03:02.00,Default,,0000,0000,0000,,times the positive impedance of
Dialogue: 0,0:03:02.00,0:03:05.56,Default,,0000,0000,0000,,the inductor minus\Nthe impedance of the capacitor.
Dialogue: 0,0:03:05.56,0:03:09.40,Default,,0000,0000,0000,,When this quantity is positive,
Dialogue: 0,0:03:09.40,0:03:14.75,Default,,0000,0000,0000,,we'll say that the impedance has\Na net inductive characteristic.
Dialogue: 0,0:03:14.75,0:03:18.90,Default,,0000,0000,0000,,When this quantity here is negative,
Dialogue: 0,0:03:18.90,0:03:22.67,Default,,0000,0000,0000,,we'll say that the overall effect\Nor that the overall nature of
Dialogue: 0,0:03:22.67,0:03:27.23,Default,,0000,0000,0000,,this combination here\Nwould be net capacitive.
Dialogue: 0,0:03:27.23,0:03:30.47,Default,,0000,0000,0000,,Now, there are times when\Nit's convenient to talk about
Dialogue: 0,0:03:30.47,0:03:33.70,Default,,0000,0000,0000,,not impedance but 1 over the impedance.
Dialogue: 0,0:03:33.70,0:03:35.51,Default,,0000,0000,0000,,So the impedance is a measure of
Dialogue: 0,0:03:35.51,0:03:42.94,Default,,0000,0000,0000,,the circuit's tendency to\Nimpede the flow of electrons.
Dialogue: 0,0:03:42.94,0:03:45.62,Default,,0000,0000,0000,,One over the impedance becomes a measure of
Dialogue: 0,0:03:45.62,0:03:49.95,Default,,0000,0000,0000,,the circuit's ability to conduct electrons.
Dialogue: 0,0:03:49.95,0:03:51.81,Default,,0000,0000,0000,,We refer to that as,
Dialogue: 0,0:03:51.81,0:03:56.83,Default,,0000,0000,0000,,call it capital Y and it's\Nreferred to as admittance.
Dialogue: 0,0:03:58.40,0:04:02.86,Default,,0000,0000,0000,,It also is a complex quantity consisting of
Dialogue: 0,0:04:02.86,0:04:07.52,Default,,0000,0000,0000,,a real part G that is called conductance,
Dialogue: 0,0:04:09.33,0:04:15.28,Default,,0000,0000,0000,,and j times an imaginary part B, where B,
Dialogue: 0,0:04:15.28,0:04:18.85,Default,,0000,0000,0000,,the imaginary part of the admittance\Nis called or is referred to
Dialogue: 0,0:04:18.85,0:04:28.55,Default,,0000,0000,0000,,as the susceptance, S-U-S-C-E-P-T-A-N-C-E.
Dialogue: 0,0:04:28.68,0:04:33.97,Default,,0000,0000,0000,,So we have impedance in\Npolar or rectangular form.
Dialogue: 0,0:04:33.97,0:04:36.94,Default,,0000,0000,0000,,We have admittance in\Nrectangular form and of course,
Dialogue: 0,0:04:36.94,0:04:41.23,Default,,0000,0000,0000,,it can also be written in polar form also.