EEVBlog

Dave explains the fundamentals of Kirchhoff's Current Law (KCL) and Kirchhoffs Voltage Law (KVL) leading up to how they might be used in the 2nd part of the video here:
• EEVblog #820 - Mesh & ...
DC Fundamentals Playlist: • Electronics Tutorial -...
Forum: www.eevblog.com/forum/blog/eev...
EEVblog Main Web Site: www.eevblog.com
The 2nd EEVblog Channel: / eevblog2
Support the EEVblog through Patreon!
/ eevblog
EEVblog Amazon Store (Dave gets a cut):
astore.amazon.com/eevblogstore-20
T-Shirts: teespring.com/stores/eevblog
Donations:
www.eevblog.com/donations/
Projects:
www.eevblog.com/projects/
Electronics Info Wiki:
www.eevblog.com/wiki/
💗 Likecoin - Coins for Likes: likecoin.pro/@eevblog/dil9/hcq3

[@RupertHandford]

Absolutely fantastic to have fundamental Friday back. It's been too long!

[@Mtaalas]

You have no idea how long I've waited for you to do these two videos :D Not that I personally need them anymore, but because I know so many that do. You're a great teacher. Keep it up :)

[@EEVblog]

+Mtaalas I've been meaning to do the for a long time!

[@adamadamhoney]

+EEVblog Cheers Dave, a lot of mechanics will benefit from my lack of teaching skill and your brilliant articulation of concepts. Much love, keep up the brilliant work!

[@DaSnipz]

Where were you 20 years ago when I needed a GOOD teacher... Some people have the knowledge but are horrible at passing it on. You sir, have both, the knowledge and the skill to explain it clearly... Keep up the good work!

[@oRufiSo]

FUNdamental Friday's are awesome. I love learning through fundamental Fridays, and the entertainment from mailbag Mondays and also the entertainment/learning through teardown Tuesdays.

[@321crash]

Love the fundamentals and theory videos!! I would love it if these types of videos came out more often. I love to learn the tips, tricks, and technical knowledge I need to be a better EE.

[@rockmick10]

I graduated in July 2015 and i am trying to keep my mind alive with these laws. But dude, where were you in my 2nd year -_- ,. you could have practically played Jesus in my life at that point in my life. This video is very clean. kudos

[@blakeb.2871]

Yes, a really great teacher indeed. A true public service. Aussie awesomeness!!!! Greetings from Kansas City, Missouri - in UMMERIKA!!!!

[@jerrybonbonifacio6970]

Everything in EE is no exception to know the fundamental forever , that's a real E Engineer -Thanks Dave to all your videos-

[@rapte100]

Thanks Dave, this video was definitely worth your time. You have explained the most fundamental laws of electronics in a very simplistic manner.

[@cbgadget100]

Tear to my eye. So many university memories. You explain it better then any before you. Great job!!

[@zlotvorx]

+Corey Busuttil University? This is first year high school material!

[@cbgadget100]

+zlotvorx not the high school I went to haha. They only just brushed over simple simple electronics in highschool.: this is a switch. This is a battery. Close the switch. Light turns on. And that's it

[@DirkBERTH]

Thanks Dave for your blogs!

[@montreadormontrez9378]

Awesome video. We need more of these fundamental Fridays!!

[@clems6989]

Great reminder video Dave.

[@jn777]

Thanks Dave, I like the way you teach fundamentals, is like a friend teaching you instead of a teacher :D

[@gds7012]

Perfect timing... I have an exam in 3 days, and a little refresher is always helpful.

[@MaximeLavigne]

Awesome Dave, I have been waiting for this for a long time :D Your explanation resonates a lot better with me then standard textbook

[@ppdan]

3:14 Evil zero suddenly popped on my screen :D 3:35 WTH that whiteboard is magic!!!

[@ellisgl]

+ppdan I noticed it too. Great editing!

[@godsdelightjude2382]

Loved it... Clear ,precise ...got the concept. Thanks.

[@jerrybonbonifacio6970]

Thanks Dave to all your videos

[@markallen200]

Great job talking in the real world Dave...Love it!!!

[@petersdrue]

Wish I knew of these videos when I was in my undergrad. These probably came out about the time I was in these classes.

[@drakecassidy2942]

Thank you sir. Your energy is great!

[@stahlight]

Taught far better than my college professors did! Well done

[@AniviaS]

Great Video, i will start referring to it when i get asked about Kirchhoffs law

[@missing1person]

best teacher.. amazing explanation.

[@michaeloosthuizen2383]

Most excellent explanations, thank you!

[@Subbestionix]

I LOVE this basics stuff! Although I'm in an physics andvanced course. It realy helps me getting into this stuff!

[@ibrahimarif8509]

you saved me a lot of hassle for my circuits course :) thank you!

[@philfount10]

At first I was like, Wait, it isn't Friday, then I remembered Australia is like 14 hours ahead of Ohio.

[@EEVblog]

+philfount10 I released 8:30am Friday in the real world :-P

[@philfount10]

+EEVblog Ah, I see. :D

[@thisaintnofoolingaround4722]

+philfount10 Same here

[@batterydudellc961]

+philfount10 Same thing happend to me just now. You the man Dave!!

[@ElmerFuddGun]

+philfount10 - Na... you all are wrong. It's not Friday for another hour. Not until 12 AM in beautiful British Columbia, Canada! The BEST place on Earth!

[@achmadpriyanto761]

i can't understand it when i was in school. but now i can. thanks you for this and others such as capacitors( 3 videos). very informative.

[@matthew8077]

Oh my god, thank you for this. You managed to put it in a way that makes sense for me.

[@AntoineLeGrand610]

This would of been useful 2 days ago, had my physics exam a day ago... In the end I still managed to understand but you explain way better than my teacher!

[@kamingcheng4830]

Love it, back to the basic!

[@edwarddjan8319]

Thank you for the video!

[@DelphijustinBiz]

thanks,that helped me figure out a question on my electronics course

[@igorsartemjevs]

Great tutorial, cheers

[@patricasong]

please continue making videos about circuit theories and analysis. include capacitors and inductors too :) great job!

[@gabrieleruffano1856]

thank you SO MUCH! i study eletronics in italy, the book i have isnt so good at explaining, and maybe skipping classes wasnt the best, thanks for helping me out! i dont know you but i heard from you from the italian youtuber MVVBlog, i dont know if you know him. Again, thank you! Kirchhoff is a pain in the stomach!

[@blownEFI]

Yaayyy ... I love Fundamental Fridays!

[@Nichoalsziv]

this is great! more basic stuff please

[@gavinandrews8541]

+Stragemque Agreed. RC, LC circuits etc. Filters. Transistors/MOSFETs, Really liked the OpAmp video.

[@happyday.mjohnson]

THANK YOU! I agree you are a great teacher. I learn a lot. I'm hoping you'll cover thevenin equivalent. Heck, i wish someone like you would take the Art of Electronics and make videos chapter by chapter. I'd pay for this.

[@audiocrush]

Love it! Fundamentals Friday videos went a bit short lately^^

[@YuGiOhJCJ]

Kirchhoff's laws is one of the first course I had at school. It is very fundamental. It is as important as the Ohm law (U = R x I). That's a pleasure to learn again this through your videos. I would like to learn more about capacitors and transistors. How to check that a capacitor is working? How to measure that it is conform to the value in Farad given by the constructor? How to calculate the charging time of a capacitor? How to check that a transistor is working? How to check that it is NPN or PNP? Is there a simple schematics to see that it is acting like an automatic switch?

[@rescuebox7]

We JUST talked about this in physics 2 yesterday, about the only thing I understood that day.

[@szoszaty]

Thanks Dave, you are a very good instructor. If I may suggest, that would be nice to make complex circuit explanations, e.g. in the Varta battery charger videos but on advanced level (ADC, DAC, multiplexers, etc.)

[@_lost._.zeny_]

Really helped me...... Thank you 😊

[@MsStrej]

Awesome, thank you!

[@surrealist303]

lifted a lot of fog from my eyes - many thanks sir!

[@fieldsofomagh]

We'll have to call you "Professor Dave" after watching this video. Hard to understand concepts are made easy peasy .I'ts hard to whack Dave,s university of knowledge.

[@nikkoderic]

I miss this kind of videos. =D

[@jeremyhall7259]

I took an Electrical Engineering class last semester (I'm in high school) where we had to do calculations on Kirchhoff's laws, I loved watching this video! I hope to get a degree in EE one day!

[@fredinit]

Did you?

[@quartapound]

Great work, keep it up Dave!! AC or Motor Theory next?!!? ;)

[@user-gr5do8nk7e]

wow! that was interesting and i learned a lot of stuff! thanks!

[@monerprokash4320]

best explanation and your t shirt is also good.

[@DrRChandra]

One of the easiest applications I can think of is lighting up LEDs. Let's say we have a 6V ( 4 x AAA ) battery and a 2.5V, 30mA LED. What value resistor will operate the LED at close to maximum brightness? KVL to the rescue. The resistor has to drop 6V - 2.5V = 3.5V. KCL to the rescue. Current flowing through the LED must be the same as the current flowing through the resistor, or let's say for safety margin, 25mA. Then apply Ohm's Law, R = E/I, or 3.5 V/ 0.025A = 140 ohms. What's the power dissipated by the resistor? 87.5 mW, so a 1/4 W, or even a smaller 1/8 W, will do.

[@chillierdavro]

Strangely enjoyable ;)

[@gutsngorrrr]

Wish I had you at college all those years ago explaining this, as I would have understood it a lot quicker.

[@GreensladeNZ]

Just finished my physics exam, this would have been helpful last night

[@fastlingo]

I think you should make more videos like these, some fundamentals and intermediate level electronics and maybe mixed with real applications, it's very hard for people who were not trained in electronics to get started when everybody seems to speak a foreign language when they speak about electronics

[@a.x.marcus4627]

Thank you!

[@nychold]

There's a layer of abstraction missing here. KVL and KCL are derived from Maxwell's equations, where the charge buildup is defined as 0. If you have a circuit that does build up charge, KVL and KCL won't work correctly. It's a minor thing, but a trap for young players, as you put it.

[@joshuapauldleon5251]

thank you so much sir

[@kyloshalo6440]

Thank you

[@luyfljf862]

More of fundamental fridays pleas!!

[@tHe0nLyNeXuS]

Great video, but the way you pronounce Kirchhoff reminds me of the Italian word "carciofo", which means artichocke! XD Remember, it's supposed to be German... :P

[@janakapriyadarshana5835]

It is really interesting the way yu are trying give the mathes to learner... Pls do critical Maths in simple way in the future....

[@VaupellGaming]

nice.. next up i guess is thevenin ? :D As a student, we almost constantly use thevenin's theorem, on later* th semesters. where KCL/KVL almost stricktly on 1,2 semesters. Good tutorial/video enjoyed it.

[@RapiBurrito]

+Eqvaliser Really? How do you make the calculations to polarize transistors in basic electronics? How do you analyze multiphase circuits? Saying KCL KVL is only used in the first semesters does not make sense to me at all... Maybe you have a very different curriculum?

[@KX36]

+Eqvaliser hasn't he already done thevenin and norton or did i imagine that?

[@KX36]

+RapiBurrito you use kcl and kvl without realising because they're so bloody obvious

[@leppie]

+Eqvaliser You dont even need to go there. Slap in an opamp with unity gain, and you solve most problems :D

[@BHBalast]

You're amazing.

[@denzil7311]

you are dope!!!! you make it too exciting to learn it

[@steverobbins4872]

Very nice video. Thumbs up! I only saw one mistake. On KCL you showed that you can arbitrarily assign the direction of current flow in each branch, and you just have to keep the node equation consistent with your assignments. That's good. But in regard to KVL, you forgot to show the voltage polarity on each branch, and didn't mention that these too can be arbitrarily assigned, as long as the loop equation is consistent. Anyway, I just thought some viewers might find this helpful.

[@andrija8506]

NICE THANKS MAN YOU REALLY HELPED ME!!!!!!!!!!!!!! I LOVE YOU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[@bangkokhomes]

Dave, great. Thanks needed to get that.... Mike bkk

[@ronaldoporraful]

i like your videos i live in brazil and I record all your videos to study and improve my english.

[@DJ_Cthulhu]

Ahhh. That brought back fond memories of Physics 101 ... :-)

[@ronettreker]

Fundamentals>Repair>Teardown>Mailbag>Review>miscellaneous

[@rabje1998]

Real nice to see someone tell this in plain english. I had this in school, didn't get the hang of it. You tell it, it all seems clearnow! Might need to kick my teacher for not being clear and clumsy. Good on ya dave, really looking forward to part 2! Roy van den Berg, The Neteherlands

[@Nater_Sk8er]

Can you do these or have you done these for basic transistor characteristics? such as talking about BJTs MOSFETS, early voltages, gm, beta, etc! Would be fantastic!

[@truboxl]

EDIT: Ok I guess you are using the voltage drop concept so E1 and E2 is positive because they are producing the voltage... If for me, using conventional current direction, -E1+Vr1+E2+Vr2+Vr3=0 and then rearranging it will get E1-E2=Vr1+Vr2+Vr3 too! Thanks for teaching me.

[@MrDoneboy]

Your body equals the sum of it's parts, so it makes perfect sense!

[@Leonelf0]

since we're at basic stuff, could you just ramp up? like, a bit "more advanced" every friday until you are at rf voodoo?

[@DataStorm1]

On the topic of playlists, I seen a vast variety of when those videos where uploaded... but are completely out of order in the playlist..... hmmm

[@mcconkeyb]

That takes me back, suddenly it feels like 1980 again :-).

[@frankreiserm.s.8039]

I was told not to pronounce the c in Kirchhoff. You are a fun teacher able to explain engineering as understandable as first-grade arithmatic. I make science videos ( enter Frank Reiser M.S.) and I hope that you enjoy mine. I once dropped an op amp ic off of the Empire State Building. When it hit the ground, it turned into a 555 timer ic. Go figure. Frank

[@joopterwijn]

Dave, now with AC and a spool and capacitor 😜

[@syproful]

Master tutor

[@ecospider5]

This is interesting I just noticed if you want 3 batteries in a circuit to increase voltage you don’t have to have them all in one place. You could technically spread them across a circuit. I wonder how this could help 200 feet of 48v outdoor lighting.

[@POLYAL0899]

all those that gave this a thumbs down were probably people that thought basic maths was a waste of time when they were pimply gobshites at school ♪♪ well done dave..... you'd be great at 'stand up ' also thats for sure

[@ninonjie5581]

Bravo

[@dooterino]

When solving nodal analysis with Kirchoff's current law you don't need to take the algebraic sum, right? You can just do a normal summation and solving the systems of equations will yield negatives when necessary? Just a little fuzzy on it still, despite a midterm for it quickly approaching

[@KX36]

next do maxwell's equations.

[@ianbertenshaw4350]

How about a tutorial of lenz law and also how litz wire works .

[@andrewgc19881]

yay fundamental Fridays... where engineers spend their Fridays....

[@PauloConstantino167]

Fundamental's Friday.....LMAO this guy is Comic!

[@user-su5sq5ib3i]

Bingo! I understand! Lol. Thank you!!!

[@dheerajathrey7285]

where does he get those shirts from?

[@TomLeg]

Seems to me it should by I_0 + I_1 + I_2 + I_3 = 0, where I_0 & I_1 are positive because they are flowing into the node, and I_2 & I_3 are negative because they are flowing out of the node.

[@Hudmyq]

Dear all, can anyone tell me what useful of KCL and KVL is in real life? Does it only helpful when you have a circuit diagram？ But if you want to some circuit are you going to use this method ?

[@samwells4103]

Would the current entering a node, be the same as the current exiting a node, if we added a small length of largely undersized cable at the exit of a node? Would the current at the start of the circuit change massively, to suit the undersized cable added, even though the undersized cable might only add a minimal increase in resistance? Because the wire gets hot really quickly, therefore increasing the resistance more and more, therefore reducing the current at start? Does KCL state that this only works with appropriate and/or standardised cable sizes? Also what happens if we just have on big cable from here to mars? would the current measured on earth be the same as the current measured on mars? I know the cable would have to have a huge cross sectional area to make this feasible in practice, but does this means if we did had a 50mm squared cable from here to mars and tried to send 10A down it, we would measure the same amount of current (0A) all the way along the whole cable?

[@samwells4103]

I know my examples are bad and I've realised they're stupid lol, but I'm just struggling to understand how current can be the same, the further and further it travels. It must be lost somewhere, somehow.... eventually.

[@toomoii]

1 dislike? must have been Faraday

[@aeroscience9834]

toomoii well, he was right

[@AlanLiefting]

Dave, where does the magic smoke factor into Kirchhoff's Current Law?

[@montreadormontrez9378]

+Alan Liefting When the equation divides by zero instead of summing to zero

[@montreadormontrez9378]

+Alan Liefting When the equation divides by zero instead of summing to zero