AC Basics Inductors in AC Circuits

How inductors act in AC circuits.
Here is the video on capacitors in AC Circuits:
• AC Basics Capacitors...

[@johnthomas4050]

Wow, almost 60 years since I dealt with this stuff - and I still (sort of) remember it! HA! Thank you sir, well done! :)

[@sweetblues3230]

in my journey of electronics I learn from comparing components what they do and what will gonna happens . and I'm thankful teaching electronics fundamentals online so opportunity to learn online it's blessing for me and everyone to learn electronics for different purposes they love

[@wolfganghiesmayr8745]

Good film! You made a very good job!

[@MrDoneboy]

Great one, Bob. I hope you replay the videos that show the RCL circuits in series, and parallel, as well!

[@musamabaso1106]

Thanks

[@johnthomas4050]

Sir: Might I humbly request that you you label each of your curves on graphs - e.g., i (sub-C or L), v (sub-C or L), etc. _ my old eyes don't detect the colors so well, nor does my feeble memory remember which is which). Again though, well done, and many thanks for making your videos. You shall be duly rewarded! cheers, jt 8-)

[@user-mz6ur9re5j]

perfect👍👍👍

[@davidbeer100]

Excelente

[@gregorykotoch5045]

My mind is blown to learn that voltage can be pushing in one direction and current can be flowing in the opposite direction on the same wire and at the same time. Also, I noticed that as current went up, voltage went down, but I'm not sure how this can be since it seems to contradict ohms law, where when voltage increases, current also increases. What am I missing here? And also in other videos you said that in order to have current flow there must be resistance and voltage. How then can there be more current with less voltage?

[@mikesradiorepair]

In a nutshell it's not a passive resistor. Capacitors and inductors are reactive components where voltage and current are not in phase. Remember, "ELI the ICE man". ELI = voltage leads current in a inductor. ICE = current leads voltage in a capacitor.

[@Slovenija_patriot]

@gregorykotoch5045 Yes when I first learned it I was confused too. You shouldn't confuse Ohm's law with inductors and capacitors. Ohm's law V = I * R stands for ohmic resistance. As voltage across resistor goes up current goes up (they are in phase and have the same shape). But for capacitors and inductors you should look at this two equations which are very important for understanding how they work. Inductor voltage: V = L * di/dt Capacitor current: I = C * dv/dt. If you look at the formula for voltage across inductor you can see that voltage is proportional to inductance and change of current. So the voltage is the highest when current is changing the fastest (when the line on the graph is most sharp/vertical) and lowest when it is changing the lowest (when the line on the graph is mostly flat). If we know look at the formula for current across capacitor we can see that the current through capacitor is proportional to capacitance and change of voltage across capacitor. So the current is the highest when voltage is changing the fastest (when the line on the graph is most sharp/vertical) and lowest when it is changing the lowest (when the line on the graph is mostly flat). In summary voltage across inductor is dependent on how fast the current changes not how big the current is and the current through capacitor is dependent on how fast the voltage across capacitor changes not how big the voltage is.

[@Slovenija_patriot]

@gregorykotoch5045 Also about why the voltage and current across capacitor and inductor are sometimes in different directions. Inductor opposes change in current by inducing voltage in such direction that it opposes change in current. So when current rises the induced voltage opposes direction of current, but when it starts falling the inductor induces voltage in such direction that the current keeps going. That's why induced voltage is not always the same polartiy as current and voltage source. Know about capacitor. Capacitor voltage changes the most when current is the higest (that's because it charges the most when current is the highest). And there is no current when the voltage across capacitor is highest because capacitor is full and can not take any more charge. Capacitors and inductors are opposite to each other. That's why current and voltage do not need to always be in the same direction.

[@gregorykotoch5045]

@Slovenija_patriot I wanted to remember to thank you before I forgot for your well thought out answer to my questions. I will have to look deeper into the formula you posted.

[@garypoplin4599]

18:16 - That was cold.

[@gerardsagliocca6292]

Your coverage of inductors was faster than your coverage of capacitors, for some reason(s) . This is unfortunate. For example to prove my point, with capacitors you went through much details and you spent much time doing the graphs of voltage and current. Then you showed the graphs when capacitor was the Source in detail. However, with Inductors, you simply said I will change colors on the capacitors 's graphs ! You shouldn't have done that, in my view, because these 2 "rascals" are problematic because of the confusing nature of these electrical components and it takes a lot of details to show beginning students, that these 2 problematic components can be mastered with some careful explanations. And you did that detailed coverage with capacitors but you did a mortal sin when you began with Inductors, as most Math teachers often do in calculus coverage of some topics. Math teachers will often say, "Oh, the rest of this solution is obvious and never show the many steps why it is indeed "obvious" ! So I give you a C grade instead of a A grade. You tried and you were doing great and then you either got tired or bored with the subject matter, and you ended up getting an average score. Maybe, next topics in AC or transistor circuits, you'll get much better grades. I know teaching electronics or higher level math topics is not easy, but if done with care and all steps are laid out, where clear understanding is attempted, that the students gains incredible insights and long term understandings and real learning is gained for all students. At this time, I am now reminded of a math modern major topic known as " Linear Algebra". Most run of the mill, math teachers do a mediocre job at explaining the mysterious but very important modern math topics with matrices, determinants when solving large numbers of simultaneous system equations. However, trying to understand how to work with large matrices and eigen values and eigen functions is very confusing to beginning technical students and even math majors. Math majors learn how to do the mechanics in getting answers but have no idea what it all means !!! Even MIT professors can't clearly explain what Linear Algebra really all means ! Then comes along some KZbin teacher showing Linear Algebra using graphical pictures and it all becomes clear why a student needs to know Linear Algebra and why one uses the methods and the "mechanics" typical done by math majors and others using Linear Algebra techniques. The name of this KZbin teacher goes by I think, "3 Blue 2 Brown" . This teacher goes very fast in his presentations, but his graphical methods go a long way to get a good understanding why a technical person or math major follows math steps to get solutions to large matrices containing system equations to model various complicated systems relating to complex electrical systems or complex mechanical systems or any complicated system that uses linear equations to describe that system's functionality and you want to know how stable it will be under various excitations or forcing functions chosen by the system designer(s). In conclusion, explaining ALL the steps, in a slow manner, should be considered important thing to do so all students gain a deep and clear understanding of the subject matter being discussed by a teacher. If steps are skipped or left to the beginning student to try to figure out , then don't be amazed that most students get low understanding and then low grades. We saw this phenomenon during the 2 year COVID 19 crisis, where the Teachers Union told the CDC that children had to learn with using a computer App. We should not be shocked that all the 4th graders in an upstate city all the students Failed math, reading and English tests ! Teachers Union shoved a bad policy on all students and an entire generation of young students will pay the price for a Teacher Union horrible , selfish policy foisted upon a vulnerable young children who could not fight back against this political group that has gotten worse since the 1970's. All they want is more money and benefits but don't want to be accountable for what parents and society demand that children are properly taught the basics so they can succeed in life and not end up in prison because they could not read and write or do basic math. Good teachers are necessary because society excels when people are well educated ! Good luck on next electrical topics. .

[@Slovenija_patriot]

I too saw that he didn't go into as much detail with inductors as capacitors. But still his explanations are very good.

[@Festus2022]

if inductor voltage =Ldi/dt and V-source =Ldi/dt, then why do the inductor and source voltages have phase differences as shown in the graphs @ time 19:58 It doesn't appear that V-source=Ldi/dt at all, and yet the equation V-source=Ldi/dt is used to derive the current through inductor. Totally confusing.

[@Slovenija_patriot]

Well you would be correct if there was only inductor in the circuit but there is also a resistor in series with inductor. The voltage of the source seperates between inductor and resistor. So that the sum of instantanous voltages of resistor and inductor would equal source voltage. v - source = i * R + Ldi/dt. And I am talking about instantanous values not RMS values because you can not directly do sum of RMS voltages to get RMS voltage of source. But you can directly sum instantanous voltages to get voltage of source. But you would be correct if there was only inductor in circuit. Then all the voltage would have to be across inductor and the voltage of inductor would be in phase and in equal value as voltage of source. Hopefully this clears your confusion.

[@Festus2022]

@@Slovenija_patriot Thanks a lot!

[@Slovenija_patriot]

@@Festus2022 No problem.

[@Sctronic209]

How is j used in the formula.

[@carultch]

It refers to a 90 degree phase shift of the waveforms. When voltage and/or current is represented as a complex number, this really represents a superposition of a sine wave and a cosine wave. The real part represents the sine wave's amplitude, and the imaginary part represents the cosine wave's amplitude. Multiplying a phasor by j*w, will shift it to lead the original waveform. Dividing a phasor by j*w, will cause it to lag the original waveform.

[@leonsoviac5380]

Ok but Xc=-1(2*Pi*C*F) is not very linear.

[@superdtp1630]

So? what is your not understanding?

[@Slovenija_patriot]

@leonsoviac5380 You are correct. The graph of capacitive reactance to frequency is not linear. But in the video he just wanted to show that the capacitive reactance decreases with increase in frequency.

[@carultch]

It is, if you graph it on a double log plot.

[@Slovenija_patriot]

@@carultch Well I don't know about that but if you graph the capacitive reactance to frequency and use equation Xc = 1/2pi*f*C you would get a hyperbola line which is not straight line like with inductive reactance.

[@carultch]

@@Slovenija_patriot I'm aware of that. If you graph log(Xc) as a function of log(f), you will get a straight line.