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Correction: We actually do create intentional transmission lines in circuits to have a specific impedance/filtering characteristic. It's mostly used in RF and high frequency.
A beautiful animation on signal transmission and reflection which is an often confusing key concept in transmission lines and systems. Thank you to all those who prepared this and made it available !
This is the Best channel which successfully explains complicated rules, theories and pure basics of electric in an very clear and understandable way with very good animations. Very well done Eugene please go on producing vids!
You can help translate this video by adding subtitles in other languages. To add a translation, click on the following link: th-cam.com/users/timedtext_video?v=ozeYaikI11g&ref=share You will then be able to add translations for all the subtitles. You will also be able to provide a translation for the title of the video. Please remember to hit the submit button for both the title and for the subtitles, as they are submitted separately. Details about adding translations is available at support.google.com/youtube/answer/6054623?hl=en Thanks.
The switch causes the input voltage to the circuit to be a step function, which mathematically is the sum of an infinite number of AC waveforms. In general, whenever a switch opens or closes, this creates transients, where the inductance of the circuit plays an important role.
JP Carcamo, no you can not upload my videos to another channel. The only way to provide a translation is through the link above, which adds subtitles which people can choose to view when watching the video on my channel. And by the way, this particular video already has subtitles available in Spanish. Thanks.
I work on J 1939 data links quite often. This explains the role of the terminating resistors. Now I better understand the transmission line at a more fudamental level. Thanks Eugene.
The music goes from "Ah, yes, you see the voltage moves like a gentle wave across the wires, the voltage bobbing lazily up and down at its output," to "AAAAH F*** ELECTRICITY"
The style of these videos is fantastic. The pace and vocalization are perfect. The only thing I would add as a critiques is that you can never restate/rephrase a concept too many times for the uninitiated.
Always loved the art style of the videos and the narrator's voice. She enunciates like Microsoft Sam. The voice and animations work together to give the videos a surreal feeling that's pleasant and unique. Keep making these videos. I watch them all.
I got to give props to the animator working with the music director on this project and also to the voice actor that changes to a much more sinister tone to extenuate the real-world implications this simple animation has
I have been experimenting with a single wire Transmission line feeding a single wire antenna element and the system s presenting an infinite Impedance to the source (I am using Impedance matching and the line is presenting no apparent losses on the single wire transmission line and very effective TEM wave radiation at the antenna. I love your Videos. Your channel has helped me with my Radio Experimentation more than any other information source. Love It !!! 🙏❤️🙏 Keep up the Great Work. VK3VKE.
You have the best illustrations about engineering! Your videos are of excellent quality and high instructive value. Thank you for making the world a less strange place
Have you considered making videos like this for substation concepts? As an Electrical Engineering student, I think it would be really beneficial for us to see the different substation configurations at work via the animations this channel offers. Just a thought. Thank you for all that you do!
What a great explanation!!! I've recently studied about the signal transmission and reflection in transmission lines to present a group work at the college. This video showed me in a more illustrative way how it works. Excellent!!!! It's good to have this type of content available on the internet. Great work!!!! It would be awsome if you post more content about transmission lines!!! I follow your channel and watch all videos that you post.
Wow, I can't believe that so may people are worried about the music or the reference to Einstein. I work with transmission-line reflections all of the time and this is a great animation of exactly what is going on at a nano-second time-frame. Look carefully at each capacitor charging and the direction and magnitude of currents as the edge propagates through the conductor. My only suggestion would be to relate this animation (in real-time) to what you would see on an oscilloscope, because this is the information that you have when you are chasing down these problems. I wish I had something like this decades ago when I was trying to grasp these concepts in college. Thanks for the great animation.
0:55 *The fact that the signal cannot travel faster than c has nothing to do with the capacitance or inductance of wires, it is just because the electric fields propagate at the speed of light (c)*
The video xas excellent as always, but it would be really interesting if you could make a second video explaining why this effects do happen instead of just showing them, in order to reach a better understanding of this phenomena.I know I may be asking too much for a TH-cam video, but I'm pretty sure you could make this happen. Great job! I love your videos!
Kritsu, this phenomena happens because the last inductor in the chain wants to keep the current going, so this current goes into the last capacitor, and as this last capacitor discharges, the signal is reflected.
+Physics Videos by Eugene Khutoryansky Wow great summary, fantastic video as always. I am disapointed in the human race for this channel not having more subscribers.
At 1:10, I would have "inductance slows the current below the max speed through wire". Not that it is less than instantaneous which would violate special relativity. I don't see special relativity coming into this at all.
The bit about relativity is total nonsense. There is no prohibition against information travelling at speed C.. but in a practical transmission line, the L & C form time constants that limit the speed of transmission. This is the concept of velocity factor - which is the fraction of C at which the signal propagates. If you want to transmit information at C, then radio waves or other light (laser..) through the vacuum of space does that nicely. But via any physical medium, speed is always sub-C.
@@drlegendre Your comment says information can travel at c, which is true. The narrator said information can't travel *faster* than c, which is also true.
*The fact that the signal cannot travel faster than c has nothing to do with the capacitance or inductance of wires, it is just that the electric fields propagate at the speed of light (c)*
Would like to see the waves aka oscilloscope pictures at the end of the transmission line. Not literally, just what would the waveforms look like if a non-interacting oscilloscope were theoretically possible.
Attaching an oscilloscope changes the waveform, because of the capacitance of the oscilloscope probe (and also possibly because of the resistance of the oscilloscope probe).
Excellent visualisation of something that confused me initially in my degree course, partly because reflections are not really part of everyday experience. Indeed, even now I hadn't appreciated that this happens with DC as well as AC!
That's cool. Phone lines are a good example of a transmission line, you can actually measure the capacitance and we do it from the CO when someone reports a trouble. We can sort of get an idea of if there's even a phone plugged in based on the capacitance. Or if the line is even connected at CO. If the capacitance is 0 it means it might be open right at the frame locally. This got me thinking... wonder if DSL modems do some kind of impedance matching when first plugged in. That's probably what the "training" cycle is for. This reflection is also known as VSWR in RF terms. It will happen if the antenna is not proper for the frequency you're transmitting at. (I sound like I know what I'm talking about, but honestly most of this is over my head, just been doing lot of reading latetly. :P )
I think you should've spent more time explaining this - to someone like me who's never heard of the concept of reflection in signal transmission, this video wasn't sufficient to make me understand how it works. Also not a fan of the music in the second half. Criticisms aside, there's too many good things to say about your videos to fit in a single comment, and I still absolutely love your videos. You easily deserve 10x the subs!
Rizwan, this phenomena happens because the last inductor in the chain wants to keep the current going, so this current goes into the last capacitor, and as this last capacitor discharges, the signal is reflected. And thanks for the compliment about my videos.
What confuses me is at around 0:40, why does the voltage drop at the first capacitor as the current continues down the cable? Why doesn't the wire just achieve the maximum possible voltage as the current gets to each part of the wire, and then just stay at that voltage until it finds a way to discharge?
Although it doesn't answer your question, it's interesting how the configuration looks like a series of low pass filters. The transmission of a pulse and its reflection might have to do with some elementary properties of capacitors and inductors? IDK.
I noticed that there were several questions about why the voltage is doubled at the end of the open circuit. Perhaps a few sentences can shed a bit of light. Important to note that this video is about AC on a transmission line, and I address here a DC pulse on a wire. Imagine an open circuit supplied by a battery and a switch. If you do this in a real circuit, you can throw the switch, then measure the voltage at the open end. It will be battery voltage. Now ask yourself how this happened in slow motion. The switch is closed, sending a pulse of current down the line. The pulse will be at battery voltage. Imagine that the pulse is a step pulse...that is, it is like an abrupt change in voltage passing down the line. The video here correctly models the capacitance and inductance of a transmission line, but we can ignore that for this time. When the pulse arrives at the end of the open line, current is not zero...it has some value fixed by the system, and is pointed in the direction from the battery to the end of the line. However, the current in the line AT the open is zero. The incident current cannot abruptly fall to zero. Charge must be conserved. But no current is leaving the line, so there must be an equal and opposite current coming from somewhere. It is the reflected current produced by the arrival of the pulse, and that reflected current derives from a "reflected" voltage. Current has direction, but voltage does not, so "reflected" here simply identifies a voltage; it does not imply direction. If the reflected current is equal to the forward (transmitted pulse) current, as it must be to have zero current at the open end, the voltage driving it must be the same as the voltage driving the forward current. These two voltages, for the forward and reflected currents, don't have direction, and simply add at the open end. Without getting into the complexity of source and termination impedance matching, we can say that this reflected pulse travels back toward the battery. At the leading of the reflected pulse, the voltage is twice the battery voltage, but the reflected current, equal to the forward current, and opposite in direction, will cancel the forward current, leaving a zero current in its wake. In an ideal generator, we would see that the open circuit voltage of the generator is twice its design voltage. Imagine shorting the line toward zero length, and ask what happens as length decreases toward zero. In this video, the mechanical pieces are already in a wave motion before the pulse reaches the open end. Realistically, at steady state, an open in a DC circuit has no current and the voltage at the open end is the same as the generator. Realistically as well, in a very short time, the DC pulse behaves as described above, but line resistive losses and impedances affect the steady state condition. This is not meant as a complete analysis, but rather as a way to justify the comment about the voltage at the open end being twice the source voltage. An experiment with a square-wave signal generator and oscilloscope connected to one end of a pair of long wires open at the end will actually show a 2 step voltage trace: the first step showing the pulse as it leaves the generator; the 2nd step to nearly twice the first, as the pulse reflects from the open end and arrives at the generator. All of these videos by Eugene Khutoryansky are first rate.
Transmission-line theory shows that for all types of TEM mode transmission lines (coaxial, parallel-wire), the basic equations of voltage and current variation over the line are dV/dz = - (R + jwL)I, and dI/dz = -(G + jwC)V in which R, G, L and C are distributed parameters. A derivation of this expression maybe found in several textbooks. . Transmission lines, operated in the radio frequency range and at higher frequencies, are generally modeled and analyzed using distributed parameters (inductances and capacitances), because the quasi steady-state conditions (that had allows us to write the capacitor reactance expression as 1/2πfC in the lumped regime of analysis) breakdown in transmission lines of lengths which are greater than the free space wavelengths of the signal. Thus, transmission lines are commonly analyzed considering the propagation of energy by the electric and magnetic fields (electromagnetic waves), around the conductors of the line; fields don't travel, the wave travels. It would be instructive to understand Current, the conduction process and Voltage at the fundamental level before progressing to a discussion of transmission line theory. Electrostatics and circuits belong to one science not two as in the following two videos: i. th-cam.com/video/TTtt28b1dYo/w-d-xo.html and ii. th-cam.com/video/8BQM_xw2Rfo/w-d-xo.html The sustenance of an electromagnetic wave between the conductors is because of two time-varying field processes, i. a changing magnetic field produces a curly electric field (Faraday’s Law), and ii. a changing electric field produces a curly magnetic field (Maxwell’s added term to Ampere’s Law). It is not possible in this post to discuss in more detail the distributed parameter approximation of transmission lines. The last frame References in video #1 lists textbook 4 which discusses these topics in more detail using a unified approach and provides an intuitive understanding of distributed capacitance and inductance of transmission lines.
Great video, as always! It would be great if you made a video explaining AC power transmission (what happens in power transmission lines). I am an electrical engineer and I have studied transmission theory in Electromagnetics Course, abut I could never conceptualize or imagine what actually happens in transmission lines.
If the two conductors here go to infinity, then the voltage will remain steady, at the input DC voltage, as the step passes down the line at about 0.7C. The direct current that flows charges up the capacitance and builds the magnetic field. The voltage to the left of the transient does not oscillate as shown at 40 seconds +, but remains steady. There is no change in the voltage to the left of the transition until a reflection returns due to an anomaly in the line.
Light don't require conductive path, like wires etc, but yes it is slowed by optically dense molecules, and there is what electric and magnetic field interacts and slows down
I love your videos, they help me so much. I have two thing unclear to me in this video: 1. What causes the current flow from the capcitor's blue plate to the battery negative pole. The potential there never changes. 2. Why is the current flowing through the inductor's side always goes in uniform direction? the potentials difference there is like a wave, so I think the current should flow to one direction in one branch and simultaneously to the opposite direction in another branch. Can you help me to figure that out? You can see an illustration for both questions at 1:34 Thank you so much
You are really asking the perfect questions. Why is there current flowing from a capacitor? A capacitor is non-conducting. But there are electrons moving, hence there is a current. One thing we need to keep in perspective, is that WE choose what is zero volt (the negative pole of the battery). Our whole earth may be at plus 500 volts, but still we take our meter and say: the battery has a negative and a positive side, and the negative side is called the zero (Volt) point because the potential difference is 1.5 Volt. But this is all relative. You could look at it as like a magnet. It has a North (plus) and South (minus) and in the middle there is the Bloch Wall (zero magnetization). Look at a battery as if it was a magnet. Same for the capacitor. So now I managed to answer question one. As for question two. I need to ask a question myself first. Does the animation show a real life event? If you take a 1.5 Volt battery and connect it to a long wire of coax. Will there be (as in the animation) a constant flow of current? Or will there only be a tiny blip of current taken from the battery and then stop flowing? I can not imagine I can empty a 1.5 Volt battery on a wire of coax. It is open ended. Only at a certain frequency the coax will respond as a resistance, but not for DC voltage. Well, that is what I think. I learned electronics 30 years ago and I don't use it so I could be wrong.
Great job, as always. You made my engineering career easy to understand with your videos. If you could make a video talking about Laplace and transfer functions would be awesome. Anyway, excellent video!!
Thanks. I am glad to hear that my videos have been helpful. I plan to eventually make videos on Laplace and transfer functions, though if you have not already seen it, you may be interested in my video on imaginary numbers, as I talk about functions of complex variables. It is at the following link. th-cam.com/video/bIY6ahHVgqA/w-d-xo.html
information doesn't travel. Information exists. Models encoding information can have such limitations, like when you speak, the entire process involved from neurons to mouth and tongue moving air to transmit a copy of an idea.
HELP PLEASE ! Though the video provides the best explanation I ever had on the subject I need some help here. The capacitors (line capacitances) can be charged up to a potential equal to the potential supplied by the D.C. source at max. When charged up to that a potential, they will cause an equilibrium and thus no current will be able to be transmitted in any direction, so how come there is a reflection
The reflection is caused because the inductor wants to prevent the current from changing, so even after the last capacitor is fully charged to the voltage of the DC source, the inductor will cause current to keep flowing through it, causing the voltage to go even higher. The capacitor then wants to discharge, causing the reflection.
Imagine the whole wire is just a single inductor. All the voltage provided is resisted by the wire. All resisted voltage must either be released as heat or "work" or stored (like a capacitor). No heat or "work" was implied to exist in the video. Therefore, all voltage provided must have been stored. Therefore, all the stored voltage must equal the voltage provided. Therefore, the provided voltage + the stored voltage = double the voltage. The doubled voltage must return back to the source when it has reached the end of the line.
This is why you can get improved sound from different cables in audio systems. Or the way you lay cables and wiring in and audio system matter. There is some actual science and physics behind it. Less exotic components and more how the proper components can be engineered to be at optimal performance.
I think the model is missing the source's output impedance, which is needed to achieve the right conclusions about the voltage provided by the battery at its output terminals, and the levels of voltages achieved in steady state in the line. I think that is why the videos are finished before they reach steady state (how do the capacitors and inductors look after a while when at the end there is a shorting bridge? The battery provides a voltage, while the line becomes a short circuit -> boom! - Infinte current?). Also, including the resistance along the line in series with the inductors would really help to see the behavior of electricity along transmission lines.
Not clear why at 2:20 "double the value of DC input voltage". Is that due to stopping of current and inductor trying to keep it on? But why exactly double? Why not infinite rice in voltage?
Nice idea to animate it this way! Although it wasn't specifically mentioned in the narration, it also shows how the signal gets distorted by travelling through the transmission line. The sharp edged pulse becomes smoothed out.
Something is not clear for me : The appearence of parasitic elements (capacitance and inductance) is happening when the lenght of the line is upper than the wave lenght of the signal, if not the kirchof law are applied and we have a located circuit. But when we talk about DC signal we cant speak about this condition, yes the frequency is 0, but is there other condition in DC case about the line lenght? Also how dc current could flowsimply through capacitance, this should take time te charge, then to discharge? thanks
daam good video deff subscribing, it would be really nice to hear a personal voice though maybe the person credible for the idea of how to visualize it, the components raising a lowings in thier grid is a completely new but really really good way of showing the voltage thanks for ur time makin these videos i wish i woulda have found all these before i spent 15 grand on college lol
Fantastic educational video as always. It's interesting to hear the physicist's explanation of EE material. I didn't follow the explanation about the second from last example, with the short. "The voltage is reflected but flipped upside down." What is meant by this? Thank you
I think maybe you could be more explanatory on your videos and stating always why something happens. This would mean more time for your videos but I believe they'd be even more watched. Like them a lot by the way.
Great animation, but using a sort of mechanical analogy is not the best idea to explain how electricity works. I think that using fluids is a better idea. Appart from that, It's a great work!
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How about an antenna or three phases transmission line without neutral wire? Could you elaborate what happens in antenna? Thank you very much
Are these transmission-lines standing waves?
Correction: We actually do create intentional transmission lines in circuits to have a specific impedance/filtering characteristic. It's mostly used in RF and high frequency.
Muy interesante, gracias ❤
Great. That video show us the difference between a Teacher and a teacher.Simple as that.
Thanks.
A beautiful animation on signal transmission and reflection which is an often confusing key concept in transmission lines and systems. Thank you to all those who prepared this and made it available !
Someone at TH-cam is looking out for me. Every time school covers a subject I'm stuck on, this channel always pops up in my recommended shortly after.
This is the Best channel which successfully explains complicated rules, theories and pure basics of electric in an very clear and understandable way with very good animations. Very well done Eugene please go on producing vids!
Thanks for the compliment. More videos are on their way.
I've been reading about this and looking at diagrams showing this arrangement. This animation really clarified what I've been reading.
I am glad my animation was helpful. Thanks.
You can help translate this video by adding subtitles in other languages. To add a translation, click on the following link:
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Thanks.
for dc inductance is zero ?
The switch causes the input voltage to the circuit to be a step function, which mathematically is the sum of an infinite number of AC waveforms. In general, whenever a switch opens or closes, this creates transients, where the inductance of the circuit plays an important role.
How about video on depletion region in a diode.
@@EugeneKhutoryansky Hi, can I create a channel to upload these videos in spanish, translated by me?
JP Carcamo, no you can not upload my videos to another channel. The only way to provide a translation is through the link above, which adds subtitles which people can choose to view when watching the video on my channel. And by the way, this particular video already has subtitles available in Spanish. Thanks.
THIS IS A VERY INTERESTING GRAPICAL REPRESENTATION ON HOW THESE VARIABLES AFFECT THE CIRCUIT PROPERTIES. THANK YOU, FOR THIS EXPLANATION!!
Thanks.
I work on J 1939 data links quite often. This explains the role of the terminating resistors. Now I better understand the transmission line at a more fudamental level. Thanks Eugene.
Glad my video was helpful. Thanks.
The music goes from "Ah, yes, you see the voltage moves like a gentle wave across the wires, the voltage bobbing lazily up and down at its output," to "AAAAH F*** ELECTRICITY"
🤣🤣🤣🤣
The style of these videos is fantastic. The pace and vocalization are perfect. The only thing I would add as a critiques is that you can never restate/rephrase a concept too many times for the uninitiated.
Dude, your genius for explaining complex subjects in simple, easy to understand ways is scary. Thanks.
Thanks for the compliment.
Damn these videos are so frkin good. Bless whoever created this
Thanks for the compliment about my videos.
Always loved the art style of the videos and the narrator's voice. She enunciates like Microsoft Sam. The voice and animations work together to give the videos a surreal feeling that's pleasant and unique. Keep making these videos. I watch them all.
Thanks for the compliment.
Such a cool video! My signal transmission class was a total nightmare; I hope others have better luck.
I got to give props to the animator working with the music director on this project and also to the voice actor that changes to a much more sinister tone to extenuate the real-world implications this simple animation has
I love the video! The content, the animation, the pace, the narrate, the music, literally everything! Thank you !
I have been experimenting with a single wire Transmission line feeding a single wire antenna element and the system s presenting an infinite Impedance to the source (I am using Impedance matching and the line
is presenting no apparent losses on the single wire transmission line
and very effective TEM wave radiation at the antenna.
I love your Videos.
Your channel has helped me with my Radio Experimentation more than any other information source.
Love It !!! 🙏❤️🙏
Keep up the Great Work.
VK3VKE.
Thanks. I am glad my videos have been helpful.
You have the best illustrations about engineering! Your videos are of excellent quality and high instructive value. Thank you for making the world a less strange place
Thanks for the compliments.
Have you considered making videos like this for substation concepts? As an Electrical Engineering student, I think it would be really beneficial for us to see the different substation configurations at work via the animations this channel offers. Just a thought. Thank you for all that you do!
THANK YOU so much eugene khutoryansky you have just cleared all the concepts of transmission
Thanks.
What a great explanation!!!
I've recently studied about the signal transmission and reflection in transmission lines to present a group work at the college.
This video showed me in a more illustrative way how it works. Excellent!!!!
It's good to have this type of content available on the internet. Great work!!!!
It would be awsome if you post more content about transmission lines!!!
I follow your channel and watch all videos that you post.
Thanks for the compliment, and I am glad that you like my videos.
We always use termination resistors at work for building networks. Always struggled visualising what it was doing till now. Nice video.
Thanks.
Wow, I can't believe that so may people are worried about the music or the reference to Einstein. I work with transmission-line reflections all of the time and this is a great animation of exactly what is going on at a nano-second time-frame. Look carefully at each capacitor charging and the direction and magnitude of currents as the edge propagates through the conductor. My only suggestion would be to relate this animation (in real-time) to what you would see on an oscilloscope, because this is the information that you have when you are chasing down these problems. I wish I had something like this decades ago when I was trying to grasp these concepts in college. Thanks for the great animation.
Thanks.
0:55 *The fact that the signal cannot travel faster than c has nothing to do with the capacitance or inductance of wires, it is just because the electric fields propagate at the speed of light (c)*
Excellent video, I can watch this all the day over and over again and not getting bored even for once :D
Hats off to your effort. I couldn't get it all. Maybe I am not that with my basic understanding.
Excellent visual demonstrations. It's really helpful for understanding what's happening. Thanks.
Thanks for the compliment.
If you like this video, you can help more people find it in their TH-cam search engine by clicking the like button, and writing a comment. Thanks.
The video xas excellent as always, but it would be really interesting if you could make a second video explaining why this effects do happen instead of just showing them, in order to reach a better understanding of this phenomena.I know I may be asking too much for a TH-cam video, but I'm pretty sure you could make this happen. Great job! I love your videos!
Kritsu, this phenomena happens because the last inductor in the chain wants to keep the current going, so this current goes into the last capacitor, and as this last capacitor discharges, the signal is reflected.
+Physics Videos by Eugene Khutoryansky Wow great summary, fantastic video as always. I am disapointed in the human race for this channel not having more subscribers.
What's the song at 1:59?
I have a dout can you explain?? please...
In Dc transmision there is no inductance effect so how we transmit the signal or electricity?
At 1:10, I would have "inductance slows the current below the max speed through wire". Not that it is less than instantaneous which would violate special relativity. I don't see special relativity coming into this at all.
I thought exactly the same.
The bit about relativity is total nonsense. There is no prohibition against information travelling at speed C.. but in a practical transmission line, the L & C form time constants that limit the speed of transmission.
This is the concept of velocity factor - which is the fraction of C at which the signal propagates.
If you want to transmit information at C, then radio waves or other light (laser..) through the vacuum of space does that nicely. But via any physical medium, speed is always sub-C.
@@drlegendre Your comment says information can travel at c, which is true. The narrator said information can't travel *faster* than c, which is also true.
*The fact that the signal cannot travel faster than c has nothing to do with the capacitance or inductance of wires, it is just that the electric fields propagate at the speed of light (c)*
@@nielsdaemenElectric field propagation and capacitance/inductance are not unrelated concepts.
Like how I felt like I was playing Halo and learning at the same time.
Would like to see the waves aka oscilloscope pictures at the end of the transmission line. Not literally, just what would the waveforms look like if a non-interacting oscilloscope were theoretically possible.
Attaching an oscilloscope changes the waveform, because of the capacitance of the oscilloscope probe (and also possibly because of the resistance of the oscilloscope probe).
Excellent visualisation of something that confused me initially in my degree course, partly because reflections are not really part of everyday experience. Indeed, even now I hadn't appreciated that this happens with DC as well as AC!
Glad my video was helpful. Thanks.
That's cool. Phone lines are a good example of a transmission line, you can actually measure the capacitance and we do it from the CO when someone reports a trouble. We can sort of get an idea of if there's even a phone plugged in based on the capacitance. Or if the line is even connected at CO. If the capacitance is 0 it means it might be open right at the frame locally. This got me thinking... wonder if DSL modems do some kind of impedance matching when first plugged in. That's probably what the "training" cycle is for. This reflection is also known as VSWR in RF terms. It will happen if the antenna is not proper for the frequency you're transmitting at. (I sound like I know what I'm talking about, but honestly most of this is over my head, just been doing lot of reading latetly. :P )
Thank you! It helped me in Guided Waves topinc in the electrical engineering
I am glad my video was helpful. Thanks.
Un'ottima rappresentazione grafica delle costanti distribuite e del loro effetto sulla propagazione del segnale lungo la linea
Perfect video to understand the basics principles of transmission lines!!!
Thanks for the compliment about my video.
I think you should've spent more time explaining this - to someone like me who's never heard of the concept of reflection in signal transmission, this video wasn't sufficient to make me understand how it works. Also not a fan of the music in the second half.
Criticisms aside, there's too many good things to say about your videos to fit in a single comment, and I still absolutely love your videos. You easily deserve 10x the subs!
Rizwan, this phenomena happens because the last inductor in the chain wants to keep the current going, so this current goes into the last capacitor, and as this last capacitor discharges, the signal is reflected. And thanks for the compliment about my videos.
What confuses me is at around 0:40, why does the voltage drop at the first capacitor as the current continues down the cable? Why doesn't the wire just achieve the maximum possible voltage as the current gets to each part of the wire, and then just stay at that voltage until it finds a way to discharge?
+Rizwan Awan (TheOnlyRizzy) this had also stumped me. Usually these videos are brilliant but I feel that this one was too short.
Although it doesn't answer your question, it's interesting how the configuration looks like a series of low pass filters. The transmission of a pulse and its reflection might have to do with some elementary properties of capacitors and inductors? IDK.
It is the flywheel effect that causes reflections, I guess?
I noticed that there were several questions about why the voltage is doubled at the end of the open circuit.
Perhaps a few sentences can shed a bit of light.
Important to note that this video is about AC on a transmission line, and I address here a DC pulse on a wire.
Imagine an open circuit supplied by a battery and a switch.
If you do this in a real circuit, you can throw the switch, then measure the voltage at the open end.
It will be battery voltage.
Now ask yourself how this happened in slow motion.
The switch is closed, sending a pulse of current down the line.
The pulse will be at battery voltage.
Imagine that the pulse is a step pulse...that is, it is like an abrupt change in voltage passing down the line.
The video here correctly models the capacitance and inductance of a transmission line, but we can ignore that for this time.
When the pulse arrives at the end of the open line, current is not zero...it has some value fixed by the system, and is pointed in the direction from the battery to the end of the line.
However, the current in the line AT the open is zero. The incident current cannot abruptly fall to zero. Charge must be conserved. But no current is leaving the line, so there must be an equal and opposite current coming from somewhere.
It is the reflected current produced by the arrival of the pulse, and that reflected current derives from a "reflected" voltage.
Current has direction, but voltage does not, so "reflected" here simply identifies a voltage; it does not imply direction.
If the reflected current is equal to the forward (transmitted pulse) current, as it must be to have zero current at the open end, the voltage driving it must be the same as the voltage driving the forward current.
These two voltages, for the forward and reflected currents, don't have direction, and simply add at the open end.
Without getting into the complexity of source and termination impedance matching, we can say that this reflected pulse travels back toward the battery.
At the leading of the reflected pulse, the voltage is twice the battery voltage, but the reflected current, equal to the forward current, and opposite in direction, will cancel the forward current, leaving a zero current in its wake.
In an ideal generator, we would see that the open circuit voltage of the generator is twice its design voltage. Imagine shorting the line toward zero length, and ask what happens as length decreases toward zero.
In this video, the mechanical pieces are already in a wave motion before the pulse reaches the open end.
Realistically, at steady state, an open in a DC circuit has no current and the voltage at the open end is the same as the generator.
Realistically as well, in a very short time, the DC pulse behaves as described above, but line resistive losses and impedances affect the steady state condition.
This is not meant as a complete analysis, but rather as a way to justify the comment about the voltage at the open end being twice the source voltage.
An experiment with a square-wave signal generator and oscilloscope connected to one end of a pair of long wires open at the end will actually show a 2 step voltage trace: the first step showing the pulse as it leaves the generator; the 2nd step to nearly twice the first, as the pulse reflects from the open end and arrives at the generator.
All of these videos by Eugene Khutoryansky are first rate.
very good animation and very good explanation ❣️❣️
Thanks for the compliments.
Brilliant visualisations! Clear and concise and intuitive!
Thanks for the compliment.
I love that song and the video was great. I'm now studying impedance canceling.
Wow! Wasn't even aware of this phenomenon. Thanks a lot.
Transmission-line theory shows that for all types of TEM mode transmission lines (coaxial, parallel-wire), the basic equations of voltage and current variation over the line are
dV/dz = - (R + jwL)I, and dI/dz = -(G + jwC)V in which R, G, L and C are distributed parameters.
A derivation of this expression maybe found in several textbooks.
.
Transmission lines, operated in the radio frequency range and at higher frequencies, are generally modeled and analyzed using distributed parameters (inductances and capacitances), because the quasi steady-state conditions (that had allows us to write the capacitor reactance expression as 1/2πfC in the lumped regime of analysis) breakdown in transmission lines of lengths which are greater than the free space wavelengths of the signal.
Thus, transmission lines are commonly analyzed considering the propagation of energy by the electric and magnetic fields (electromagnetic waves), around the conductors of the line; fields don't travel, the wave travels.
It would be instructive to understand Current, the conduction process and Voltage at the fundamental level before progressing to a discussion of transmission line theory.
Electrostatics and circuits belong to one science not two as in the following two videos:
i. th-cam.com/video/TTtt28b1dYo/w-d-xo.html and
ii. th-cam.com/video/8BQM_xw2Rfo/w-d-xo.html
The sustenance of an electromagnetic wave between the conductors is because of two time-varying field processes,
i. a changing magnetic field produces a curly electric field (Faraday’s Law), and
ii. a changing electric field produces a curly magnetic field (Maxwell’s added term to Ampere’s Law).
It is not possible in this post to discuss in more detail the distributed parameter approximation of transmission lines.
The last frame References in video #1 lists textbook 4 which discusses these topics in more detail using a unified approach and provides an intuitive understanding of distributed capacitance and inductance of transmission lines.
Great video as always, Eugene. Can't wait for more.
Glad you liked it. More videos are coming soon.
again a very good Video.
I always enjoy watching these
Thanks. I am glad you liked it.
Your visualisation of voltage seems pretty unique (and its very descriptive)
i also gained some insight on (partly-) reflected waves in general.
Came for the explanation, stayed for the metal 🤘🏻
BRAVO !
What a great explanation of signal propagation !
sbf
Thanks.
That's a 10'th order low pass filter.
I love the way you have simplified the video!
Great Video and 3D animation, adjust playback speed to 1.25x to be even more interesting..
Incredible visualizations and great education value. Thanks!
Thanks for the compliment.
I love it. Your animation is very advantageous.
Glad you liked it.
I enjoyed the background musical choice of this video. All of it.
-Congrstulations for the vídeo. -Brilliant and Smart explicstion.
Educational system must be use the adventage of actual tecnology
Thanks for the compliment.
2:00 Signal: gets reflected
Music: Intensifies into raucous energetic rock music
So much helpfull information perfectly presented, thanks!
Finally understood, why there have to be Resistors at the end of CAN wires.
oh my God! it's amazing!!!! I understood what I couldnt understand before. u r fantastic! WoW
Glad you liked my video. Thanks.
@@EugeneKhutoryansky Please make one about AC transmission lines!
Great video, as always!
It would be great if you made a video explaining AC power transmission (what happens in power transmission lines).
I am an electrical engineer and I have studied transmission theory in Electromagnetics Course, abut I could never conceptualize or imagine what actually happens in transmission lines.
Music is so cool .. Lol, not so fitting , but interesting
Just re-play the video for the music. :)
Just reply for curiosity
Wow great content, love this type of ed video, very clear
So educative and future promising
Love watching the actual effect and behaviour of electrical circuit
your 3d works are wonderful, thanks a lot. keep making more videos.
now it all makes sense! :D great video and great use of illustrations to explain
Betten than my Electrical Engineering class
If the two conductors here go to infinity, then the voltage will remain steady, at the input DC voltage, as the step passes down the line at about 0.7C. The direct current that flows charges up the capacitance and builds the magnetic field. The voltage to the left of the transient does not oscillate as shown at 40 seconds +, but remains steady. There is no change in the voltage to the left of the transition until a reflection returns due to an anomaly in the line.
this channel deserves more subs...
Thanks.
Great video as always.
Thanks. Glad you liked it.
Light don't require conductive path, like wires etc, but yes it is slowed by optically dense molecules, and there is what electric and magnetic field interacts and slows down
This would be really helpful if u explained this topic to physics students after taking them to an electronics lab
great music choice 😎
Excellent explanation!!! All of your explanations are great. Thank you.
Thanks for the compliment.
Very Nicely done animation :)
really nice demonstration. Thanks
Thanks. Glad you liked it.
I love your videos, they help me so much. I have two thing unclear to me in this video:
1. What causes the current flow from the capcitor's blue plate to the battery negative pole. The potential there never changes.
2. Why is the current flowing through the inductor's side always goes in uniform direction? the potentials difference there is like a wave, so I think the current should flow to one direction in one branch and simultaneously to the opposite direction in another branch.
Can you help me to figure that out?
You can see an illustration for both questions at 1:34
Thank you so much
You are really asking the perfect questions. Why is there current flowing from a capacitor? A capacitor is non-conducting. But there are electrons moving, hence there is a current. One thing we need to keep in perspective, is that WE choose what is zero volt (the negative pole of the battery). Our whole earth may be at plus 500 volts, but still we take our meter and say: the battery has a negative and a positive side, and the negative side is called the zero (Volt) point because the potential difference is 1.5 Volt. But this is all relative. You could look at it as like a magnet. It has a North (plus) and South (minus) and in the middle there is the Bloch Wall (zero magnetization). Look at a battery as if it was a magnet. Same for the capacitor. So now I managed to answer question one.
As for question two. I need to ask a question myself first. Does the animation show a real life event? If you take a 1.5 Volt battery and connect it to a long wire of coax. Will there be (as in the animation) a constant flow of current? Or will there only be a tiny blip of current taken from the battery and then stop flowing? I can not imagine I can empty a 1.5 Volt battery on a wire of coax. It is open ended. Only at a certain frequency the coax will respond as a resistance, but not for DC voltage. Well, that is what I think. I learned electronics 30 years ago and I don't use it so I could be wrong.
Great job, as always. You made my engineering career easy to understand with your videos. If you could make a video talking about Laplace and transfer functions would be awesome. Anyway, excellent video!!
Thanks. I am glad to hear that my videos have been helpful. I plan to eventually make videos on Laplace and transfer functions, though if you have not already seen it, you may be interested in my video on imaginary numbers, as I talk about functions of complex variables. It is at the following link. th-cam.com/video/bIY6ahHVgqA/w-d-xo.html
information doesn't travel. Information exists. Models encoding information can have such limitations, like when you speak, the entire process involved from neurons to mouth and tongue moving air to transmit a copy of an idea.
Very nice Visualization
Thanks.
Great one :) To people who are confused please first check out his capacitor inductor videos and it will make perfect sense :)
HELP PLEASE ! Though the video provides the best explanation I ever had on the subject I need some help here. The capacitors (line capacitances) can be charged up to a potential equal to the potential supplied by the D.C. source at max. When charged up to that a potential, they will cause an equilibrium and thus no current will be able to be transmitted in any direction, so how come there is a reflection
The reflection is caused because the inductor wants to prevent the current from changing, so even after the last capacitor is fully charged to the voltage of the DC source, the inductor will cause current to keep flowing through it, causing the voltage to go even higher. The capacitor then wants to discharge, causing the reflection.
Thanks for the help
Imagine the whole wire is just a single inductor.
All the voltage provided is resisted by the wire.
All resisted voltage must either be released as heat or "work" or stored (like a capacitor).
No heat or "work" was implied to exist in the video.
Therefore, all voltage provided must have been stored.
Therefore, all the stored voltage must equal the voltage provided.
Therefore, the provided voltage + the stored voltage = double the voltage.
The doubled voltage must return back to the source when it has reached the end of the line.
Great video ! Keep up the good work. Much appreciated!
Thanks. More videos are on their way.
This is why you can get improved sound from different cables in audio systems. Or the way you lay cables and wiring in and audio system matter. There is some actual science and physics behind it. Less exotic components and more how the proper components can be engineered to be at optimal performance.
Any case, your videos are great
very good video. very impressive presentation
I think the model is missing the source's output impedance, which is needed to achieve the right conclusions about the voltage provided by the battery at its output terminals, and the levels of voltages achieved in steady state in the line. I think that is why the videos are finished before they reach steady state (how do the capacitors and inductors look after a while when at the end there is a shorting bridge? The battery provides a voltage, while the line becomes a short circuit -> boom! - Infinte current?). Also, including the resistance along the line in series with the inductors would really help to see the behavior of electricity along transmission lines.
Please do a follow up video, such a great topic
Exelente video Eugene
Thanks.
Not clear why at 2:20 "double the value of DC input voltage". Is that due to stopping of current and inductor trying to keep it on? But why exactly double? Why not infinite rice in voltage?
She's always Good!
And helpful.*****
Thanks.
Nice idea to animate it this way! Although it wasn't specifically mentioned in the narration, it also shows how the signal gets distorted by travelling through the transmission line. The sharp edged pulse becomes smoothed out.
Could you elaborate on what effect causes this?
i love your videos! Since I am an electronics student, these videos are extremely good. Thank you so much!
Something is not clear for me :
The appearence of parasitic elements (capacitance and inductance) is happening when the lenght of the line is upper than the wave lenght of the signal, if not the kirchof law are applied and we have a located circuit. But when we talk about DC signal we cant speak about this condition, yes the frequency is 0, but is there other condition in DC case about the line lenght? Also how dc current could flowsimply through capacitance, this should take time te charge, then to discharge?
thanks
daam good video deff subscribing, it would be really nice to hear a personal voice though maybe the person credible for the idea of how to visualize it, the components raising a lowings in thier grid is a completely new but really really good way of showing the voltage thanks for ur time makin these videos i wish i woulda have found all these before i spent 15 grand on college lol
Nice work thank you. I wish you made a follow-up video about max. power transfer and Thevenin' s theorem for equivalent resistance.
Thanks. I may make videos on those topics in the future.
Fantastic educational video as always. It's interesting to hear the physicist's explanation of EE material. I didn't follow the explanation about the second from last example, with the short. "The voltage is reflected but flipped upside down." What is meant by this? Thank you
I think it means it is reflected but 180 degrees out of phase.
I think maybe you could be more explanatory on your videos and stating always why something happens. This would mean more time for your videos but I believe they'd be even more watched. Like them a lot by the way.
Very good Video, cool 😊
Thanks.
good stuff, this helps make it easier to visualize
Great animation, but using a sort of mechanical analogy is not the best idea to explain how electricity works. I think that using fluids is a better idea.
Appart from that, It's a great work!