EEVblog 1417 - AC Basics Tutorial Part 1: Alternating Current

[@FARLANDER762]

Started playing this video and my 22 yr old software engineering major daughter sticks her head in the room and says "Is that the new video? I watched it this morning." WHAT?!?!?!?! I asked her what got her into watching EEVBlog and she said said some video had been recommended and she just started liking how Dave teaches and especially how he draws things out (DaveCAD) so it's easy to visualize. LOVE THAT KID!!!!

[@lordjaashin]

cool story, bud

[@MikeJohnMentzer]

Btw what got you into EEVblog

[@arthurmead5341]

Did not happen

[@FARLANDER762]

@@MikeJohnMentzer Don't recall. I'm sure YT recommended it for some search I did and it looked interesting.

[@FARLANDER762]

@@arthurmead5341 Damn sure did

[@designdigitalarchitecture]

Just like to say a huge thank you for your education. All you work is so apricated, so thank you.

[@lvxleather]

I second that. I've been watching the channel for years but have been binging on the crazy Aussie bloke for the past few weeks. I've learned a quite a bit, and also some pretty funny sayings. Bobby-dazzler!

[@abhijithanilkumar4959]

@@lvxleather Such an underrated channel!

[@bertblankenstein3738]

Keep him honest Sagan!

[@omniyambot9876]

thank you so much sir. I rarely comment on your videos but now I'm getting college I will take electrical engineering and you always stimulate my mind. I love your videos and I almost watched everything. I've watched you since I'm 10 years old!!

[@omniyambot9876]

also I have like your recommended test equipments I always save for used ones

[@DarkMatterX1]

That shot of Sagan at 33:35 is the best part of the vid.

[@bertblankenstein3738]

Lol

[@cannesahs]

Pure meme

[@ct1igu401]

One of the BEST explanations of AC measurement I've seen - Thanks

[@sanjayvora5986]

I fall short of words when I have to say thank you thanks for all your hardwork knowledge and all the incredible work and effort which goes into making these video . I respect you sir and wish for your long and healthy life .

[@williampmcd8548]

Your channel is a cut above. I appreciate the level of teaching you are presenting although I don't understand so much. Thank you for these videos.

[@Artopiumcom]

Whaaa!?! I'VE BEEN WAITING YEARS FOR THIS VIDEO!! THANK YOU!!

[@EEVblog]

Better late than never.

[@Artopiumcom]

@@EEVblog 😍

[@PointReflex]

Man, I sooooo missed those fundamental episodes. This is the stuff that belongs to a class room.

[@Waseem0071]

This one video is better than my 4 year Bachelor Degree in Electrical Engineering

[@triode3582]

Please do more of these videos. You're a great teacher! :D

[@romanlukichev4971]

I've heard here by far the best explanation about what RMS voltage is. I looked it on KZbin a couple years ago and videos were not so good.

[@toshineon]

This is exactly what I needed. I'm currently studying electricity, and currently we're reading about AC, transformers and generators. You made it much easier to understand than the study material I have.

[@gilbus4989]

You were so descriptive and detailed. Excellent.

[@derekloudon8731]

I love your enthusiasm. I wish that you were around in the late 60s/early 70s when I was learning electronics 👍

[@yusufat1]

Dave's teaching made my day already, but Dave's son appearing on camera made it even better

[@GeorgeWMays]

Explain to me why we love this stuff so much...! Super fun video. Appreciated.

[@stevedaenginerd]

Thank you for reminding me how much I forgot! 😲🤣🤓 Thank you for all that you've shared over the years! Glad Sagan decided to get in on the fun and use maths to take the wind out of your sails! Lol 🤣

[@rrb6544]

Great collection of calculators Dave ;)

[@michaelbarakat6095]

"Thank you very much" the least to be said for this effort Mr. David💖

[@ianbertenshaw4350]

“You’re never gunna escape AC” -someone should have told Edison that 🤣

[@onradioactivewaves]

He probably told that to his victims, just prior to electrocuting them.

[@MrDoneboy]

Tesla tried to!

[@theharbingerofconflation]

"As you can see now this Cat is fried" "Okay weirdo, I already told you I won't buy your overpriced lightbulbs!"

[@user-mr3mf8lo7y]

He would not understand.. He was a businessman not a scientist. He wanted to get direct profit not alternating one. Thanks Dave..

[@fabienb3432]

Many thanks Dave for all the work you are doing here.

[@WacKEDmaN]

nice to see Prof. Sagan keeping you honest Dave! :P ...this is another refresher i needed... thanks mate...

[@n2n8sda]

Mmm AC.. I hope this carries on down the rabbit hole into pros and cons of HFAC vs HVDC at some point! As for ripple, good on ice-cream not great in a DC circuit :)

[@bradpalmer2914]

Raspberry ripple for Ice Cream, smoothing Capacitor for DC. Don't mix them up the electrolyte is nasty 😂

[@N2YTA]

This was the best explanation of AC I've seen, thanks.

[@tincoandringa4630]

My electrical engineering education, after 1417 lectures, finally the introduction to alternating current ;)

[@williamsquires3070]

The new law says “e” (the induced stress of drivers on the motorway) = “B” (the flux density of Teslas on the motorway) x “L” (the length of the motorway) x “v” (the average velocity of all Teslas on the motorway) x “c” (the percentage of Teslas which have caught fire and become charcoal briquettes)!

[@jenniferwhitewolf3784]

🤣🤣🤣🤣👍👍👋🏻👏👏

[@ebbewertz3417]

to debate the naming defenition of AC, in dutch we have a name for everything: - DC - periodic DC - Constant DC And only when a wave crosses the x-axis ( = switch its current direction), it's AC. Then u have: - "Alternating current" (can just randomly switch current direction) - Periodic alternating current - And when avg=0 and its fully symmetrical, then its one word directly translated : "alternationcurrent"

[@57dent]

As usual Dave really interesting and well explained video. A great reminder on a lot of the theory detail that I'd forgotten! I'd really like to see a similar video on three phase power, (edit - realized I did not word correctly!) What I meant was how single phase can get converted to three phase. and the equations behind it!

[@krzysztofkozowski5375]

When calculating the RMS by integral of squares, the 1/T period should be cast away the root - I think... Thank you for GREAT tutorials. It's sad that university lectures aren't that at that high level so often. Your language is also easy to understand even for noobes ;) KEEP IT RECORDING...

[@McTroyd]

Glad the Sagan bit made the final cut! That was hilarious.

[@davidharwood297]

Loving these back to basics tutorials. 👍

[@SamTheMasterDragon]

Thank you so much for this, been struggling to get into the nitty gritty of AC power. Messed around a lot in Desmos to understand the angles but with those extra equations, it clears a lot of questions up. Thank you again for this video!

[@wadosm]

I think the maximum current peak should be at 0/180 degrees because then there is maximum change between S and N, not at 90 degrees as Dave said. But it's just detail, great work Dave :)

[@ronmuller9899]

Dave is correct. at 0 and 180, the movement of the wire is horizontal and in line with the orientation of the magnetic flux. A current is only induced in the wire if the wire cuts through the magnetic field lines.

[@minus3dbintheteens60]

I agree with op, I thought voltage peak would be when the wire is horizontal, inline with the magnet but the current comes from the movement and would peak when the wire is vertical

[@TheStefan665]

Dave, this is awesome; while there are many educational videos on youtube, your take on each subject is important, as you are the standard reference around here; keep up the good work!

[@thomasgaliana6288]

I can't wait for what is to come! Two thumbs up!

[@marcdraco2189]

Thanks for all of this Dave - I quoted you when I reviewed the Rigol 1074Z recently, only I spelled "come a guster" incorrectly. Until recently I'd been given to understand that inductors are *coils* but now (d'uh) ANY current through a wire is caused by a magnetic field (or is it the other way around or is it simultaneous) which why all components and even our PCB wires have a certain amount of inductance which can cause issues at very high frequencies! Damn my basic science and lumped component models. Back to skool (sic) I guess...

[@leogray1091]

Wow. we move on to AC now. ! Glad to see them

[@electronichaircut8801]

This is what I needed for ages.

[@rollbot]

excellent! thank you for sharing this. really impressive how you've explained things and cleared up so much for me.

[@hadireg]

I feel good whenever I see that casio calc there!! :)

[@matthewellisor5835]

Agggh! Did anyone else have an existential-rounding-error-crisis around 10:43? Well, it's close enough to pick up a thing and put the thing onto some other thing. (Show me again, those ∆v calculations, please.) "Correct within _some_ order of magnitude." was my fourth-favorite teacher's way of saying "wrong" while preserving face for his student while publicly deducting grade-points. *Edit* Good job youngin' on keeping the 'Old Man' straight. I should have watched it all through before running my trap.

[@nicwilson89]

I remember years ago when you had Sagan sat on a table or something, you two were making some sort of Lego maybe? It was something like that. He was just a wee young kid. How time flies! I always knew you'd make an amazing parent, and the young man Sagan is growing up to be certainly suggests as such! The young chappy is going to go far :D

[@Electronics_Dreams]

Siempre es bueno repasar estos conceptos básicos, muy buen video como siempre Dave!

[@Basement-Science]

The highest AC transmission line voltages these days are actually 1.2 MV btw. First used in India alongside 800 kV DC.

[@EEVblog]

Crazy!

[@kissingfrogs]

Wow

[@neglectfulsausage7689]

Try waving a car antenna around below it during a rainy day.

[@Audio_Simon]

Frickin' amazing intro to AC, I hope the rest is this good!

[@gregorymccoy6797]

Sagan is running the numbers behind the scenes and ready to call shenanigans, if necessary.

[@ilanmagen]

awesome sausage, canot wait to part 2 3 4 5 6. Thank you

[@whitefields5595]

Dave, this is you at your best

[@johnpeterson7264]

Wonderful ! Thank you so much for posting !

[@TheRealBanana]

9:27 I think a single cycle of AC can be described as an infinite series of AC waves that all sum to that single cycle, and those are all proper AC. So I'd say its still AC.

[@modrobert]

Good explanation, easy to understand.

[@DrB1900]

Another advantage to sin waves is you can combine any two at the same frequency, but any amplitude and phase, and you still get the same frequency out (just phase shifted).

[@onradioactivewaves]

Say what, you sure about that?? I for example they If they are in phase they have constructive interference - no phase shift but definitely has an amplitude shit.

[@fersunk]

Mmm, if you want constructive interference in a sinusoidal wave you need both in phase, so they add their amplitude. That's how you get 240VAC in USA, you use two 120VAC lines phased out 180 degrees

[@AndrewSkow1]

10:30 The Metric System is some weird French thing that you use. 28:11Sagan is technically correct, which is the best kind of correct.

[@petergoose8164]

Metric is something we all use directly or indirectly. The indirect way is just more complicated. en.wikipedia.org/wiki/Pound_(mass) and en.wikipedia.org/wiki/Inch.

[@colejohnson66]

@@petergoose8164 no. Only the French use metric. That’s what Andrew said

[@petergoose8164]

@@colejohnson66 Where did he say that? If he had said that how do YOU explain that the Ford Mustang uses mostly metric bolt and thread sizes. "Le Mustang"?

[@markuskivisto1425]

@33:14 Vmax=Vp-p or just Vpeak?

[@notacucumber7617]

Dave thank you! I'm so lack of your fundamentionals videos. It's been so cool, if they will be more deeper and often.

[@simonowen488]

More of this series please!

[@user-ur2mc2bo7e]

Thank you for this interesting work 👌🏻

[@CezarVideoBlog]

Thank you, well made, amazing teaching skill !

[@ppaolosan]

you are a genius of electronics!

[@CMTEQ]

@22:00 , So basically the average voltage means the negative peak and the positive peak canceling each other, like the old algebra rule (-120 + 120) = 0.

[@aldizzle]

Nice Doc Brown reference form "Back to the Future"!! I got it. LOL 5 minute 18 second mark!!

[@paulleitner8726]

Thank you for these series

[@ahmetrefikeryilmaz4432]

Most people assume that teaching is a God-given talent but it almost has more to do with knowing your shit. He knows his shit.

[@shmehfleh3115]

I used to stick stuff in outlets all the time, and I never got shocked. Now I know why: I was using the average, not the RMS.

[@SaberusTerras]

The fact that Sagan spotted the small maths error shows he has better math skills than most adult Americans.

[@lordjaashin]

why Americans? rest of the world are mathematical geniuses?? on the side note, here is your Chinese RMB for doing your part in "murica bad" propaganda.

[@primus711]

Where you get that nonsense from

[@SaberusTerras]

@@primus711 direct empirical evidence

[@primus711]

@@SaberusTerras are you talking about measurements because we use them all Tbh you are just being a m0r0n and have no evidence of anything

[@remyb718]

Team Sagan!!! We don't write a number for its beauty but because it's correct :).... just add a space and some other decimals and everyone will be happy :)

[@RiyadhElalami]

Great video Dave. Even though I live and die this stuff, your explanation was entertaining and informative

[@NoLandMandi]

Sagan is correct.

[@pauldow1648]

Super. Great peanut gallery. 👍

[@RogerCillion]

Everything that effects AC also effects DC, and vice versa. Changes occurs always in nature, but you can choose to neglect them if the total impact is small.

[@electronic7979]

Helpful video. I liked it

[@Croz89]

Am I correct in saying most modern generators put the magnets on the rotor and have the coils on the stator, so the magnetic field rotates instead of the coils? So you can do without the slip rings.

[@andymouse]

Cool ! I've been waiting for this...cheers.

[@CaspaB]

Fun fact. Edison hated AC but Westinghouse argued it was more useful as it could be "transformed" up or down to suit. This led to Edison describing those executed by Electric Chair as being "Westinghoused".

[@excitedbox5705]

I get what you mean, but AC can be stored using a rotating mass, pumped hydro, or pressurized gas. You turn it back into AC using a generator. You can't store it as charge.

[@EEVblog]

You aren't actually storing the AC electrical energy like you store DC in a battery.

[@briangoldsmith7504]

@@EEVblog I thought batteries stored their energy in a chemical reaction?

[@primus711]

You arent storing anything you are using the energy to push electrons back basically the same as pumping water back up the hill to be drained later to the bottom when needed

[@m4dizzle]

LOVE these, thank you sir!

[@neglectfulsausage7689]

Ill save you all the discussion headache. As not an EE nor an expert, the simple way to explain DC vs AC is "does the current and voltage cross the X axis, indicating reversal of either". If the answer is no, then its a DC circuit regardless of any sine waves in it. Thats why an audio signal going into an amplifier circuit is getting rectified. What difference is there if you use 4 junction diodes to rectify or you overlay a large DC voltage on top? Both cause ripples or sine waves to stay on one side of the X axis. While you're hacking up a sine wave/AC input in diode rectifying to do work, you're adding work to an audio sine wave in an amp circuit so it doesnt have to be chopped up and that signal will then work on the circuit to cause voltage changes. Thats why I like to think of amp ciruits as cloning the input signal and not as passing it along. That also makes it easier to understand distortion. A flawed copy.

[@petersage5157]

It's rather distracting how the confuser under the whiteboard keeps changing. I especially like the slide rule. AC is respective to a fixed voltage reference, thank you, the end. Doesn't matter if that reference is O VDC or 500 VDC. This is why, in choob amps, HF snubber capacitors can go to either circuit ground or HT and be equally effective, and why "lifting" the filament supply is an effective way of getting filament hum out of the audio signal.

[@minus3dbintheteens60]

I love these videos. I hope a future video can help explain power factor

[@tongordebeke1355]

Wonderful, i love fundamentals.

[@theengineer9910]

Cover transfer functions ! Great video.

[@viperidaenz1]

Are you sure peak current from the generator is not at the top and bottom, where the wire is moving the fastest through the field between north and south? Down at 90 and 270 degrees the flux density isn't changing is it?

[@kuadidzv8726]

thanks for the very nice explaination 😎

[@MikeB_UK]

Dave, having shown off a succession of pocket computers in this, how about a quick video show and tell of them? Do you actually make any use of any of them ?

[@wchen2340]

Hey can't leave me like that. I want that part 2 right now.

[@gregorymccoy6797]

Great. Love it. Do more 😀

[@KeritechElectronics]

Nice to repeat some theory, though 2πf is a lowercase omega rather than w. Wondering if RMS shouldn't be in fact named SMR :) Integrals... ugh, I'm bad at math, okay? LOL. Suffice it to say that I failed my electronic engineering studies at the technical university because of calculus. Makes me wish that at least some teachers there were as passionate and humorous as you - it would be a pure pleasure to study! Lovely Casio VFD calculator too! These teeny weeny numbers are so damn cute. I was expecting an Electroboom meme at 26:35, haha :) and the cameo appearance of your son was real cute too! With an awesome dad like you, he'll be an electronic engineer in no time.

[@stub1116]

I enjoyed this video!

[@olipito]

You didn't explain why it converges to sin when you put whatever into the filter. New video?

[@theguitaramptech]

Another perfectly informative video, Dave. A great balance of information over time….hmm… I wonder if Education=Integral of information/time. Greetings to NW Sydney from locked-down SE Sydney

[@jimstand]

The Government is limiting how much alcohol can be delivered to a person in NSW. They are opening packages and removing or not delivering the contents. When are the people going to stand up against the lack of freedom?

[@waltercomunello121]

5:18 that BTTF reference

[@J0eMega]

I believe AC is also much more efficient when distributing over long distances. Three phase power delivery is a lot more cost efficient. That and I think I read somewhere that AC is less lossy at super high voltages over super long distances.

[@JulianA-tr6pt]

I've also heard the opposite - DC being more efficient. I've never looked into it, but of course AC has its benefit of high voltage transmission and step-down substations and residential "pole pig" transformers. Less current, less copper, less voltage drop.

[@J0eMega]

@@JulianA-tr6pt According to energy education: “Alternating current (AC) is the type of electric current generated by the vast majority of power plants and used by most power distribution systems. Alternating current is cheaper to generate and has fewer energy losses than direct current when transmitting electricity over long distances.”

[@J0eMega]

@@JulianA-tr6pt However, according to engineering stock exchange: “Transmitting DC power over a long distance is inefficient. Thus AC supply is a far more efficient to transmit power. According to Siemens it's quite the opposite: Whenever power has to be transmitted over long distances, DC transmission is the most economical solution compared to high-voltage AC.” So yeah, I guess reputable people and companies have claimed both.

[@minus3dbintheteens60]

HVDC allows power transmission between AC transmission systems that are not synchronized. A long-distance, point-to-point HVDC transmission scheme generally has lower overall investment cost and lower losses than an equivalent AC transmission scheme. HVDC conversion equipment at the terminal stations is costly, but the total DC transmission-line costs over long distances are lower than for an AC line of the same distance. HVDC requires less conductor per unit distance than an AC line, as there is no need to support three phases and there is no skin effect. Depending on voltage level and construction details, HVDC transmission losses are quoted at 3.5% per 1,000 km, about 50% less than AC (6.5%) lines at the same voltage. This is because direct current transfers only active power and thus causes lower losses than alternating current, which transfers both active and reactive power. en.wikipedia.org/wiki/High-voltage_direct_current#:~:text=A%20high%2Dvoltage%2C%20direct%20current,alternating%20current%20(AC)%20systems.

[@J0eMega]

@@minus3dbintheteens60 I will look into this after work, but one glaring thing I saw is the fact it costs less because you don’t need 3 phase. AC transmission doesn’t require 3 phase. 3 phase is just much easier to work with and enables a system to transmit just as much power without requiring nearly as much material. That and it allows for easy access of both 120 and 240V for commercial use. Now mind you, idk if a single phase AC requires more or less material than a single phase DC, and if single phase DC is as easy to work with, manipulate, and monitor as 3 phase AC, as these are just things I noted off the top of my head. As for the skin effect, our power lines use bundled conductors to further mitigate that on top of using multiple phases.

[@tojo3D]

My bet is on Sagan! :)

[@RixtronixLAB]

Nice video, thanks :)

[@gower1973]

Doesn`t a perfect sine wave trace out the path of a circle and therefore you could use the area of a circle to work out the average, instead of using calculus?

[@n3r0z3r0]

Actually it is more efficient to transmit power on long distance in DC form instead of AC, and it is done in many places already.

[@KD0CAC]

Dave , or others , an idea / question and I think I have a guess . " Can not store AC " - idea is using capacitors for AC motors , they are spouse to store power [ not sure the correct term - power ] , and a general understanding of capacitors - they pass AC & block DC . So how does a motor capacitor store power for motors starting ? So my guess , the discharge is so fast [ short relative to 50 or 60 Hrz ] that the quick discharge of stored DC from capacitor , that it fits within the positive part of the AC waveform ? Any correction or confirmation .

[@williamsquires3070]

(@1:10) - I think Dave blew it! The diagram shows a peak current of 1 (amp, presumably), but then Dave points to the diagram and says, “the DC current would just be a straight line at 1 amp”. Nope, the DC current would be the same as the AC (RMS) current, which would be 0.7071 x the peak, or just 707.1 mA (for a sine wave!!) Right, Dave? 😏

[@EEVblog]

I didn't have time to build it to scale or to paint it.

[@williamsquires3070]

@@EEVblog - Paint the whiteboard?? 😐