Example: Analyzing a more complex resistor circuit | Physics | Khan Academy

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A hairy resistance problem. Created by Sal Khan.
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[@xX1234512345xX]

This video helped a lot. Considering that this video is nearly 6 years old and you'll probably never see this comment, but thanks.

[@SocksKr]

oh wow. 5 years ago this was 6 years old to you... reminds me of that history fact: "ancient Rome is as old to us as ancient Egypt was to the ancient Romans"

[@shukishan]

Michael McGrath, your comment is old and is nearly 6 years old now and you'll probably never see this comment, but have a good day.

[@masterofIich]

Hey, if you come from the future and be like: wow, there had youtube in like 2008? Have a good day ;)

[@jlgtco97]

I saw it!!

[@sonkim6876]

@@jlgtco97 Me too.

[@TheEngaged22]

Mr. Khan because of you I'm going to medical school!

[@skarpengland]

+TheEngaged22 Me too man, i am starting to really understand physics, like, shit!! Haha, i am starting to believe

[@skarpengland]

+TheEngaged22 i seriously think this channel HAS to be the one thats the most useful

[@SocksKr]

how is medical school? :)

[@iBuyBitcoin]

Your comment is 4 years old, I’m sure you have that MD by now and all this is a blur ! Lol congrats btw 👏🏽

[@TheEngaged22]

@@iBuyBitcoin lol I wish, but I am an MS-2 right now! First year of medical school was certainly challenging but very rewarding

[@cowzrule101]

0:38 - Sal: "4Ω, 8Ω, 16Ω..." - Me: "Powers of 2, next should be 32Ω" - Sal: "I am actually making numbers up on the fly: 16Ω (again)" - Me: "FFFFFUUUUUUUUUUUU..."

[@jayceel251]

ahahhahaha

[@legendkiller376]

I would be so lost without you Khan

[@HgihAsFcuk]

Dude i'm in circuits and have had no idea wtf was going on until I watched a few of these videos I'm gonna watch all of these right now

[@fbevc]

You should also make a video explaining how much is the voltage on the specific resistor in series, or current on the specific resistor in parallel. From what i've been tutoring highschoolers they have the biggest problems with this concept.

[@sonkim6876]

@xXxGucciMasterxXx No we was actually tought this at school, do you need the formulas?

[@tanjimirtiza2366]

As a Bangladeshi I'm proud of you sir. You are and always be in the hearts of us. You make our country glorified. We love you.

[@tabeen1779]

tbh lol

[@cierrapresson4163]

This was one of the most helpful physics videos I've watched! I had no idea toy could simplify a circuit so easily.

[@youriemhei]

thanks for your kindness and generosity to put up this vid for those physics learners/. :)

[@steveg1080]

I just spent an hour going over my course material and was NOT getting it at all and this video BLEW my mind and connected all the dots! THANK YOU!!!

[@tiptopmini]

Thanks for saving my grade again!! Great videos, I'm loving them :)

[@taybahkhan908]

THIS SAVED MY LIFE. Thank you so much!

[@darkinvader911]

I watch most of these videos in 1.25x speed

[@pero828]

+Abdulrahman Bink I watch most of these videos in either 1.5 or 2x speed

[@OCK1995]

my fav: 2x speed + subtitle

[@zuko8023]

I watch in 1.75

[@gailtaukuheke5152]

Saaame!!

[@theUnmeshraj]

All in 2x w/o subs

[@Mr.M1STER]

at 6:18 why would you use V = IR. That only confuses the entire situation imo. The simplest way to follow is just solve it in terms of what you are looking for, which is I. So I = V/R, which is 20V/2.5 ohms, which is 8A

[@gamingwithproc8240]

Thanks for such a wonderful video which helped me a lot , a video which was posted before my birth is really good to see

[@SankalpJain-vh8wn]

Solved it myself in 2mins...got the right ans too

[@anava84]

I wish the lectures on magnetism weren't under construction :( If light and optics are added, attending physics class will not be necessary! Thank you very much for everything you've done Sal! Your much appreciated. -PsubD

[@flippingerik]

Thank you, you have helped me on topics through two semesters of calculus and now two of physics. Always a reliable source

[@boreycheng9260]

I WANT TO KNOW MORE ABOUT COMPLEX CIRCUIT PLS MAKE VIDEO EXPLAIN ABOUT KIRCHHOFF's CURRENT LAW.

[@exceedtheman]

2:44 u messed up on the one quarter equaling to 1/16...

[@Jordanadean]

Nope, he just had sloppy handwriting. It's 1/16, not 1/4 according to the circuit diagram.

[@hockeymo]

QUESTION: In one of his earlier vids he said that the current throughout the circuit is constant but in this video he said that the current are different at diferent places? wouldn't there be a "build-up" of electrons if there different currents????

[@jassongarcia5303]

Oh My God these videos are really helpfully. This is my senior year in high school and I want to master these things so when I get to college I'll be the best in my class. Thank you for taking your time to makes these extremely awesome videos! Best wishes

[@tabeen1779]

liking your comment after 10 years, when im in the situation same as yours 10 years ago :)

[@gabigarcia457]

WOW i am taking a AC/DC course and the 4 videos really help me understand before I get too far behind. Not trying to bash the teacher but these videos would be a good acompany to any lecture. Instead of him slowing down for thos who don't understand, we can keep up with his great lectures! THANKS!!!!

[@amolm.v6]

Anyone watching this in 2019!!!!!!!! Love Khanacademy!!!!!!

[@changingspiritually9540]

Thank you so much-been using Khan Academy since primary school. I do believe you converted the 2nd 1/4 to 1/16 rather than 1/16 by mistake but regardless you make it look like it's easy. I'm currently studying AHE level 3 Engineering and I'm grateful I saw this.

[@NoahA211]

Sal Khan: helping everyone from high schoolers to engineers

[@YisiLulala]

I sat through 3 lectures over circuits and was still confused. After watching all your videos, it makes perfect sense. Thank you!!!

[@nimragauhar4838]

OMYGOD! Life has become so much easier now :) Never stop making videos please you're the BEST

[@afrighanimali]

Thank you soooooooooo much all the videos on circuits have been very helpful !!! I was wondering if you could do a video on QUANTUM PHENOMENA ???

[@parthduklan]

the last 1/4 resistor is not calculated correctly while taking the LCM

[@MrASquared100]

dude, you are legendary, from Adam Ray voice, to your methods of teaching. just a little suggestion, some videos on emf and internal resistance would be helpful.

[@quinstermyer]

wow! that was easy!

[@bosslovely27]

Easy and time saver thanks a lot

[@jmnc05]

I disagree with the comment below to some extent, only because some stuff you draw I can't read but you say what it is out loud as you are drawing it so I know what it is. These videos by the way are awesome, thanks for putting them up!

[@hugtheoboe]

YES! I got the right answer before you even finished explaining! Thank you!!!!

[@tohelphoomans.9243]

Oh myy God!! I am acquiring great knowledge from 14 year old videos!!

[@Ethan.J.C]

i gave up on the revision and notes and just enjoying the video

[@ag1293]

These videos are spectacular! I would love to hear you explain the Wheatstone Bridge if you have the time!

[@ajskilton]

it's 8A in total but this is shared amongst the parallel resistors(pathways), that's the whole point of the video!

[@Nandine2]

wow great video, although I don't really have problems understanding electronics in my physics class but this video really does give an intuitive feel. and I am not just saying that!

[@ankurgaur9729]

Simple video presentation and awesome explanation. however, there is miscalculation at point when we add starting four resistance in parallel. Addition of four resistance i.e. 4,8,16& 16 in parallel is equal to 8/5 not 2 ohm..

[@grendits]

Yea and some stuff about Op Amps would be great

[@killthecardinals]

@1sushicheese1 Yes you are, because they were added correctly.

[@metalmaniac767]

At the start I actually said, "This guy is a lunatic!" Great video :D

[@franknostradamus]

Thanks for all the video's so far, they have helped me a lot with my studies! But im still left with some questions about circuits; what will happen if you add mutiple U's (dunno the word :-) ) intro the circuit? What will happen with the flow of electrons? And what will happen if you put them in parallel? Thanks for your clear video's! Looking forward to the new video's!

[@Daski69]

very intuitional for me has always been the fact that the current in series is always the same. I think of it as a one lane racing track where a crash(resistor) will slow down the cars that have yet to drive through the crash site and the cars that already have done so, since the cars that have already done so, are in fact the cars that have yet to do so.. (trollface).. u get my point! what is less obvious though is that the voltage is the same in parallell circuits. Could someone explain?! thx

[@ishan0833]

great tutorial..

[@Melisou12]

thankk you soo much !! all your videos are very helpfull

[@MsRoseapple]

Reli helpful on my study !thank you very much!

[@MrGreene212]

Thank you.

[@GreatVgnc]

Those are second year college concepts. There are a few videos from the undergrad Yale physics video library on this but require a bit of calc. and some linear algebra (vectors, differentials, and line integrals)

[@wnqls0315]

oh wow thanks this is much easier than I thought..

[@haripriyadebnath7969]

thankyousomuch sir!

[@Akiithebest]

Do people mention him during their grad speeches? Because they should.. I know I'm going to next year, best teacher ever!

[@Parapresdokian]

சூப்பர் தலைவா!

[@griftorifto2]

@IPMountainDew I don't think finding each value of the resistance is possible only possible values for each that would make the equation true. Since there would be a huge amount of possible values It would qualify for as a problem of "Great hair density and length" ;) Finding voltage given all resistance values and current is very possible(simple) however.

[@babaksoltanfar9326]

is it possible to some videos on voltage and current dividers pleasee??

[@FLAMERNECRO]

THANK YOU !

[@SamRobertduty]

Thank you !

[@hazara67]

I love u SIR..... for all of these great vedios......!!!! thanxxxxxxxxx alot

[@esaskhan95]

My exams are gonna be starting in a week (CAMBRIDGE!) and i actually gained ALOT!..Hats off to you :) Stay Blessed!

[@krystynfrenche-vincent6911]

Thank you so much your videos always help me soooooo much without u i might fail physics

[@amandastark10]

Since the current is leaving the positive terminal of the battery, would the answer be negative?

[@GerardoSilvaMendoza]

Great video!

[@kingjoe8788]

sal PLEASE make a video on electromotive force and the difference between emf and voltage

[@MrSadik11111]

Well... I wanted him to explain how to do it when you have resistors in triangle and you want to turn this configuration to "star" (That's how we say it in France...) So this is really easy for me but... nevermind! It's still a good explanation ^^

[@TheMichaeljohnny]

Thnks u r gr8

[@boreycheng9260]

i really love all your videos

[@boeing747200lr]

What is the meaning of a hairy problem? Btw, very good explanation.

[@twosheeps3933]

My teachers need to see your videos and then prepare their lectures

[@Zander101084]

you're the best sal!

[@jennifersullivan8084]

could you add a video about adding a capacitor to a series?

[@jayceel251]

thank you!!!!!!!!!!!

[@youngamerz]

i regret not watching this during my exams as half my paper had these question and i ended up failing them.

[@akaSnockis]

Is there a video about potential difference in a circuit?

[@xxfuturerevealedxx]

GJ GJ MAN GJ hahah great tutorial buddy

[@TheUnchainedBeast]

good work (Y)

[@prantiksutradhar2894]

I thought this a lot like you!😁

[@BryanMeadows011235]

Watch it again and again until you get it or go back one video you'll then know it forever.

[@akshaydamle95]

at first i was like FFFFUUUU... too but then i saw 16 and 16 gives 8 and then 8 and 8 would give 4 and then 4 and 4 would give 2 so the net resistance can be calculated mentally

[@Ray-cr4xj]

How did he get 1/3 +1/3 =3/2? Its 2/3 no?

[@YISTECH]

@@Ray-cr4xj I’m 3 years late, but see, it’s 1/R = 1/3 + 1/3, so hes doing the reciprocal of 1/R to get R

[@fighter91]

Wait I'm pretty sure he made an error when adding up the top resistances. I think his fractions are incorrect because isn't supposed to be (4+2+1+4)/16? The last number is supposed to be 4 not 1.

[@TragTheGamer]

MAN YOURE AWESOME!!!!

[@SuperMekolo]

the formual for simple interest is Prt/100

[@SuperOwnagedude]

+aniket kesarwani the formula for compound interest is A=PR^n

[@devigopalakrishnan2909]

2:09 big hairball!!🤣🤣

[@MrPlaytiger]

Bravo sir bravo

[@fenzter5649]

I LOVE YOU KHANN!!!!!

[@Nandine2]

actually I don't get voltage dividers and EMf......(sneakily asking you to do a video on it!!)

[@okyeregideon7082]

guy try dis for me kind of confuse. Two resistors 10ohms and 20ohms are connected in parallel with emf of 12v. calculate the current passing through the 20ohms resistances..

[@haz6942]

0.6

[@okyeregideon7082]

hazal d great , i got the same answer 0.6A

[@griftorifto2]

Mmm loved me a bitta hairy circuit problems.

[@Antne2202]

First part should have been (4+2+1+4)/16 right?

[@mihirbpi]

2:08 This big hairball

[@poshablyposh]

haha thanks fo all the videos! you teach better than my teacher. really;))

[@amirrahimaftab]

1/(1/4 + 1/8 + 1/16 + 1/4) = 16/11 = 1.45 ohms (not 2 ohms). Time reference: 2:56

[@Ray-cr4xj]

How did you get to 3 over 2? One third plus one third is 2/3rds. How did it get 1.5?

[@gbmack2000]

at 5:55 don't you mean there are two resistors left in series, not parallel?

[@bboy1600]

Thanks man, You're Awesome :)

[@MariaMaria-wf7jl]

Süper

[@LoverPhantasm]

علياااا الطلااااق I LOVE YOU

[@fortum100]

the last one is meant to say 1/16, if you look closely

[@shadowofadoubt14]

I FUCKING LOVE YOU! My exam is in 7 hours