Impedance

[@jonmckay5549]

I like the explication of impedance as both mathematically and graphically! Great job!

[@wkw1333]

My final is tomorrow and I need more videos 😭

[@drb_kd]

OMG ... mine is in two days .. HOPE you did well in yours :")

[@abdulmohsenalmousa9564]

mine in 3 days :(

[@camofelix]

3 hours....

[@HellOnGames]

Mine is tomorrow too haha

[@jaypark8415]

what have these ppl done until the end of semester

[@J_H_Rahbek]

good video on this, would love some examples with vectors in the complex plain to illustrate whats happening, as well ad the impedance for RL, RC and RLC but great video dude! Love the color coding haha

[@MiCreationOfficial]

Simple concept of impedance: Imagine you're playing with water flowing through a bunch of pipes. Now, think of impedance like the pipes being twisty, narrow, or bumpy. These things make it harder for the water to flow smoothly. In a circuit, impedance is like those twists and bumps but for electricity instead of water. It's what makes it a bit tricky for electricity to move around smoothly in the wires. So, just like you'd feel resistance when pushing water through a twisty pipe, electricity feels impedance when flowing through a circuit.

[@finlayhutchinson7370]

why did you assume that i was e^jwt

[@curtpiazza1688]

Cool stuff! Thanx for showing the derivations! 🎉

[@dannysharpe8948]

What does J omega stand for though? What is the numerical value? I don't understand it

[@louco2]

Thank you for the video, this is beautiful math!

[@ignacioeugenelei7242]

9:20

[@dalenassar9152]

At the start, what would happen if you used the -jwt term? The WHOLE expression for cos(wt) is not used...so how do you justify using just a piece of it??

[@alanwj]

When you put e^(jwt) into a circuit, you will find that the output is some complex number, A+jB. Note that any complex number can be written in this form. If you then put e^(-jwt) into the circuit, you will get the output A-jB. By superposition, if the input is cos(wt) = [e^(jwt) + e^(-jwt)]/2, then the output will be [(A+jB) + (A-jB)]/2 = A. Well, in that case we can skip the second half of this process. Just find the output for e^(jwt) and take the real part.

[@ntwanakasi10111]

i have been struggling for so long with this impedance topic. thank you sir

[@sjjvddyumiherhv3709]

thank for explaining a whole semester in one video

[@jaybee1299]

What does the J represent? I'm able to follow along and have some understanding of all the other symbols and their meanings but what is J?

[@jaybee1299]

Maybe its related vectors? J represented vertical components of vectors when I was in school.

[@ShinjiCarlos]

I would rather sugest a better explanation of the concepts. Impedance is never complex. You firstly convert your input signal into a complex one just mathematicaly. Then, you work out the equations and concepts and then take back the real part. The connection has not been made as nicely. Other problem: these exponentials are NO VECTORS, but PHASORS!

[@TrebleWing]

As a beginner, this is the worst video I could have landed on. This first equation you bring to the table alone, is just everything wrong with trying to learn something fundamental from professionals.

[@techniker8745]

Eye Opening! thanks!

[@dawsonblack3332]

I can't tell if I'm being taught by Nick Cage or Robert Downy Jr.

[@nabstergaming2859]

Is this for alevels????

[@s.m.senses7199]

🙏❣

[@bartomiejpotaman6973]

is "j" just a constant in general? We did in the complex world cuz the differentiation is easier but it would be weird if we had imaginary impedance

[@maxbingen8773]

for those when it didn't click (which it didn't for me at first), the reason why I = C dV/dt is because I = dq/dt and Q = CV, combining those two, dQ/dt = C dV/dt = I

[@oskarwallberg4566]

thank you mate

[@ShinjiCarlos]

My friend, actually I didn't like so much this video. Poorly explained. You are totally right!

[@dc2prashant]

OMG 🙏 I feel my IQ is 0 ,what I remember is the spelling of impedence 🙄

[@Zurenio]

Thanks a lot.....!!!

[@johncgibson4720]

1:43 , text books usually uses a expression function called "The real part of", and the text books don't need to throw away the negative part for some mysterious preference.

[@ShinjiCarlos]

Exactly! Dude didn't use the signal as input signal, but went using exponentials as a matter of physical signal, what is not conceptually correct. It is just a math trick in this case. In oppositr to Schrödinger's equation, which is intrinsicaly complex.

[@arklanbk]

understood nothing

[@ShinjiCarlos]

This class was garbage! Look in Sears and Zemansky 3 or Haliday and Resnik. Amazing 3 books!

[@SirFancyPantsMcee]

is there an order to these things? I thought this was gonna be a basic video and its not at all

[@mfpears]

Using j is the worst convention ever

[@ShinjiCarlos]

Nope. It isn't, but this video class is garbage after all.

[@n9583]

Thx

[@praneethdhanushka207]

Dear Sir, I have a puzzle about impedance of speaker and Amplifier. When I was studying Physics at college I learned that Resistance is as a scaler ( only has a magnitude but doesn't have a direction). Impedance is also a resistance and it is measured in Ohms. But it is a Vector ( has both magnitude and a direction). Can you explain the difference between the resistance and impedance with drawing on a video??? Thanks Praneeth

[@urano4810]

Resistance is for DC circuits, so resistord only oppose the current in one direction. Impedence is caused by the changing electromagnetic field created by the alternating current (AC) which opposes the direction of the current whichever way its flowing at all times. In other words, it constantly alternates to oppose the current as the current itself alternates and this constant change is what creates the magnetic field in the first place.

[@moadtheconquer]

Thank you so much for the explication

[@sukanyaghosh24]

*explanation

[@AppleUploader]

No matter how hard I try I will seriously never understand physics. It's black magic

[@johncgibson4720]

It is not magic, it is wizardry. And the master wizard was a guy named Leonard, born German but died a Russian and buried in Russia.

[@anjum1130]

No kidding 😂

[@Power_DC_Official]

If you think you will never understand physics or anything for that matter... YOU ARE ABSOLUTELY RIGHT!

[@ShinjiCarlos]

Don't bother, mate! I don't think this is your fault. Actually, he began his video in a strange way. Firstly he talked about cosine and stuff, what is correct, since this is one of the simples form of periodic signals. But the conection between it and using an exponential was fuzzy. Someone does use exponentials because they are handy and there is a connection between them and sine and cossine functions through Euler's relation, exp(j theta) = cos(theta) + j sin(theta). But the author of the video should have emphasized that the functions we are dealing with are real valued, like the cosine mentioned at the begining. Sumarizing, you do use complex exponentials as a matter of calculus, but at the end, keep only the real part.

[@ShinjiCarlos]

For this kind of stuff, search some nice channels on electronics, dude. It makes way more sense. This kind of circuit are useful for designing low-pass filters, high-pass filters and band-pass filters. Our brains make way more connections when it sees some applications. And it is super fun! Useful for designing equalizers for electric guitars, for instance and play with sounds! So cool, mate! Don't give up! :)

[@masbro1901]

why do we have to measure the ratio of voltage to current? and what for? and example implementation in real appication... thanks..

[@ShinjiCarlos]

Dude, this is realy useful in passive and active filters. For instance, since frequency appears in the denominator of capacitive impedance, high frequency signals see a low impedancein a capacitor. The opposite for indutors. So, if you make a voltage divisor with resistor and capacitor, you may make a low-pass or a high-pass filter.

[@successmotivation2997]

Confidence!!

[@manoharp6800]

Simply I loved.. It.. You are amazing

[@adntubecnn7673]

Someone know the book from where he got all this info , please ???

[@RicardoHernandez-zr1pw]

I need something practical for troubleshooting electrical panels.

[@els1f]

That really explained impedance better than any way it's been taught to me 😄

[@wetwingnut]

You can't start with Ohm's law as an assumption, posit a sinusoidal current, use Ohm's law to calculate the resulting voltage, then take the ratio of voltage to current to get Ohm's Law back again, and claim that you have "proven" Ohm's Law. FAIL!

[@ShinjiCarlos]

Simply ridiculous

[@jan861]

How is the phase shift being accounted for?

[@chair547]

Multiply by j == 90 degree phase shift

[@pouya397]

good

[@shaikgowsya2714]

Tq

[@BecomeAWebDev]

When you pronounce the word COMPONENT the stress is on the second syllable not the first, as you are pronouncing it with the stress on the first syllable. comPONent. the caps indicates where the stress is ...

[@ps_online]

what is impedance in RL parallel circuit???

[@samirfakoua]

I’m guessing the same as resistors in parallel?

[@Freakybananayo]

This jumps straight in without explaining much

[@ShinjiCarlos]

Exactly. Very poorly explained.

[@oidjscnd9744]

I usually like Khan academy's videos. But this one was totally unclear. Didn't help.

[@jamilladambo]

It’s a series. Watch the entire playlist where he explains every single thing that led up to here

[@ShinjiCarlos]

This class is awful. The dude dind't explain just simple things. You are right. I would rather read a textbook. Halliday and Resnik, Sears and Zemansky, for instance. Maybe, I would even use some simulations from PHET Colorado to get visual insights.

[@ShinjiCarlos]

With simple things I mean how he evoked complex functions out of the blue, without emphasizing that they was used as a math trick, not as physically real. Just at the end you take the real part. There was a huge conceptual gap there. I see a lot of people in the comments expressing how they feel bad for not understanding. The ones who understand seem to have some prior background.

[@prasantikumarshee3746]

Please don't watch, all other videos are really nice but this one is not...

[@ShinjiCarlos]

This one is just garbage!

[@prasantikumarshee3746]

3:41, really dude..... how can you do this with us .😂😂

[@ShinjiCarlos]

Exactly!!! What did you prove? Nothing!!! This dude is a joke

[@viniciuslongo4622]

​@@ShinjiCarloscalm down Shinji Carlos!

[@thebirdman612]

not good

[@afr65536]

Actual explanation of what impedence is comes at 9:20

[@FixDaily]

Thanks :)

[@mastermind8047]

thanks man

[@KKShedge]

Why is Musixmatch turning on in this video?

[@threefour1598]

For me it turns on in many youtube videos recently, including this one

[@chrisnasil1752]

What is j ?

[@dirtydan6600]

j =sqrt(-1)

[@chrisnasil1752]

Dirty Dan merci beaucoup monsieur ☺️

[@johnfykhikc]

need crazy physicist teachers that talk meaning any tip guys please

[@johnfykhikc]

i need more details to understand it, I feel sad

[@ShinjiCarlos]

Hello! This class was awful! Search for another source, dude! Honestly.

[@ShenLong33]

Why you only use the exponential with the positive sign? Why not use the negative or both?

[@ShinjiCarlos]

Because this lesson is not well rounded. I think he should have said: Hey, let's imagine a cosine input signal. But, since there is a connection between cosine and complex exponentials through Euler's relation, let's work with exponentials, which are easier to work with, and just take the real part at the end. But, I am pretty sure you already know that, since you wrote it 4 years ago.

[@tnekkc]

This reminds me of EE in the 1970s at university... not much like designing power supplies in the 80s and 90s.

[@foerfoer]

If you start assuming that v=iR, it is normal that in 3:55 you obtain again v=iR, I can't see why you say you proved v=iR if it was the starting point.

[@9uweeoncbmd890]

His point through this class was to show that applying a complex signal into the equations that give capacitance, resistance and inductance would result into values of capacitance and inductance that are variable to the frequency of the signal. He obtains the resistance again without variability of frequency again despite having applied a complex signal, proving that the real part of an impedance is its resistance, while its imaginary part are the inductive and capacitive reactances.

[@Danielagostinho21]

I was thinking the same way, I think that is a falacy, "Circular reasoning" and "Begging the question"

[@anthonyskilton8634]

is this really Khan?? he hasn't proved anything !! Sal, you need to fire this guy!!

[@AnoNymous-dh2sv]

Yeah I also think what he did there is mathematically nonsense. He starts with "A) I KNOW I = V/R" and "B) I ASSUME I = XXX" so he comes back to his "I KNOW". tl;dr: You can't start with what you know and reach the same thing. You already knew it. PS. He could just say "R = V/I" and that ratio is impedance, let's find out what that is for other components. It would still make sense, probably more sense.

[@martensamulowitz347]

this was done to explain the subject, the phrasing used in this video is simply not the point here. he even said this is nothing new, this was z just to have a red line along which to introduce impedance

[@SeanMcDonnell33]

kind of wish this started with an explanation of what impedance actually is maybe with a water metaphor or something

[@NiamorH]

no please, no more water metaphors...

[@two_number_nines]

Water metaphors are already bad enough in electronics basics. Impedance is the same thing as resistance in DC circuits. In DC a resistor gives out heat based on its value and the current passing trough it. It also limits the current based on its resistance value. In AC a capacitor or inductor doesn't give out heat, but limits the current passing trough it, but instead of using the U=R*I law to calculate the current you use U=Z*I. In AC Z acts the same way as R in DC, but in AC Z depends not only on the value of the component, but the frequency of the wave supplied to it.

[@asuklej5860]

@@two_number_nines great explanation (Y)

[@andjelkastokic8706]

Really great explanation!! My question is , are you going to make a video about complex AC circuits ? @khanacademy

[@ConorFenlon]

Your speech pitch range and pattern characteristic is very close to Bill Murray.

[@alaindebotton336]

Is it Groundhog day or groundhog's day

[@alitabrizi633]

How the hell will I someday learn all of this

[@MeepMu]

One step at a time.

[@todddavid9133]

I dont understand why v and i are expressed by the same expression (e^+jwt)

[@dirtydan6600]

i=(e^+jwt) but we know v=i*R so V = R*(e^+jwt)

[@binishulman8655]

If you are talking about the latter half of the video where capacitor V=Resistor I, then first understand Euler's formula for expressing trigonometric functions as exponentials. Then, since Voltage proportional to current, they can both be expressed with cosine (or sin) function in AC circuit, just with different amplitudes - i.e the coefficients of the cos functions, which will be Imax and Vmax respectively. But if you carry these amplitudes through in the calculations shown in this video, they cancel out in the v/i ratio stage.

[@feelgoodtimez]

why do you assume i=e^(jwt)? how do you come to this assumption?

[@austink-v8261]

It's derived from Euler's equation, you can search it up

[@Enigma758]

That's an excellent question which he should have mentioned. If you research it, it turns out that e^jwt=cos(wt)+j*sin(wt) which itself is a sinusoidal. So he made a big simplification here without really telling us about it.

[@Enigma758]

Also, if he had used the original equation, the derivative would have been slightly more complex to compute, and thus taken a little more time to show in the video, but you would end up with exactly the same result. If you like, you can try it and see that it works.

[@veronicanoordzee6440]

@@Enigma758 You forgot this video is part of a series of videos. He explained everything you wrote.

[@Enigma758]

@@veronicanoordzee6440 Fair point, although perhaps a quick reminder at this point would have been a good idea. BTW, I'm not trying to be critical, I think these videos are great.

[@ZIKO1200]

great video. Thanks a lot!

[@TheCaptain14]

Great introduction to impedance

[@perfectpakka8151]

Could somebody explain me at 3:09,What's happening right there ?

[@whoeverseesthatbehappy2722]

Well as I got it, he just replaced all I's as e to the +jwt and applied Ohm's law U/I=R, looks like Sisyphean task or kind of that thing

[@manavshah6811]

waddup with SALs voice? how come he's speaking like a normal human?

[@aneeqahmed5575]

Its not him

[@barisbasturk8443]

don't waste your time by watching this. just sayin

[@GospodinJean]

why?

[@ShinjiCarlos]

Lot of conceptual gabs. Guy claimed to have proven Ohm's Law by assuming Ohm's Law as a starting point, for instance.