Resistors in series | Circuits | Physics | Khan Academy

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Resistors that come one after another. Created by Sal Khan.
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Physics on Khan Academy: Physics is the study of the basic principles that govern the physical world around us. We'll start by looking at motion itself. Then, we'll learn about forces, momentum, energy, and other concepts in lots of different physical situations. To get the most out of physics, you'll need a solid understanding of algebra and a basic understanding of trigonometry.
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[@Kai-Xi]

0:48 "If there is any such thing as reality" XD

[@panchvangapandu5349]

Derpy Hooves lol, Khan Academy getting philosophical...

[@MrSocialish]

LMAO i just came from the khan academy website to the KZbin video just to make the comment you just said! Khan is more than a person. He is an omniscient force.

[@bryllethe13]

hahahahahaa

[@hassanhamze_14]

Are you guys alive in 2021

[@AnaOhKay]

@@hassanhamze_14 are *you* alive in 2024?

[@vishnureddy3977]

"My wife will probably mind that I didn't answer" LOL

[@phalafau1258]

Marriage standards

[@midnightsilverpuppy]

"For fun let's put in a third resistor" Me: "whoa! U wild"

[@MrManwookie]

"If there is any such thing as reality" Sal's having another existential crisis :P

[@khanacademy]

Real-world wires have resistance, but in the diagrams, we assume that the non-resistor part of the circuits have no resistance (or that it has all been added to the "resistance" in the diagram)

[@lucasgdrezes]

I don't wanna be an electrical engineer, I just wanna got some questions right on the test I'm having tomorrow.

[@DonJuliusss]

RT

[@gomugomutree6075]

i hope you did well on your test

[@hey9530]

Five YEars Later -> How'd u do on the test?

[@lucasgdrezes]

@@hey9530 Well, I graduated high school without any problems. The video was helpful!

[@lucasgdrezes]

@just some guy tired of life Yessir.

[@biotch77]

"but what we know in reality what is happening, if there is such a thing as reality..." sal, you're awesome.

[@cierrapresson4163]

I love that Sal managed to slip in a little philosophy while he was at it.

[@aaronsilver-pell411]

you can't really do physics well without philosophy

[@genchani8537]

OMG this is so simple. When my professor explained this part it sounded so damn hard. I wish you were my professor :) Btw, thanks a lot for these videos.

[@GreatMasterOogway]

we all wish he were our professor :'(

[@skarpengland]

So, i used Khan academy all last year when i did my basic introductory course in medicine. now, i am doing physics and chemistry to hopefully enter medical school... and didnt you know, Khan can help you in physics as well! THANKS!

[@fadyfarouk8635]

good luck!

[@skarpengland]

i got accepted! i also got exactly the stuff in this video, in my physics exam. talk about coincidence

[@fadyfarouk8635]

***** wow good job, I hope I get accepted too. Have a great college period!

[@ernestosaboia]

4:58 Hey Sal, thanks for all your teaching and sharing, so here is my small contribution: Electricity in a wire moves at 2/3 of speed of light, electrons move very slow :)

[@csdvrrecordingstudios7272]

U learn something new every day 😊😊

[@Becca11Dance]

His voice is so relaxing :)

[@Sheikisspear]

Hahahaha

[@seanki98]

0:48 deep

[@user_z11]

Yeah

[@kschwab14]

"It's my wife, she'll probably mind that i didn't answer but anyway...." haha love the dedication

[@mitch3850]

Sal is the man. I attend university in Victoria, Australia, and one of my classes is Electrical Systems. The lecturers are very smart but they forget that many students haven't dealt with the basic concepts of electrical functions, and tend to skip over them. I'm 12 weeks in and about to sit my exam, and before seeing these videos I was really worried. But SAL MAKES IT SO F***ING CLEAR. If I get a pass, it's due to Sal and Khan. Thanks man!

[@greenscreenasshole]

Did you pass though

[@mitch3850]

@@greenscreenasshole I actually did!

[@tonynasaofficial]

​@@mitch3850 congrats!

[@Hiandbye95]

I think the amazing thing about your videos is that I understand everything you explain. This is something I rarely experience in school. xD

[@vomitingteddy]

should have answered the phone man

[@Daski69]

I'd like to initiate this comment with a huge THANKS to you Mr Khan, you're a genius! Second, I'd like to contribute with a personal idea, to people who have a hard time with understanding some basics when it comes to circuits, like I used to have. Why is it so that the voltage over the "more powerful" resistor is higher than the other. Well, voltage is defined as energy/charge. It requires more energy to get pass the big resistor than the small, simple. Over and out.

[@reezis1619]

After watching 6 minutes of the video I just wanted to say that you are AMAZING at explaining things. You make everything so easy to comprehend

[@jaydaappleton6463]

He is such a good teacher. I literally came here knowing nothing about circuits, and after watching this video I somehow am completely ready to complete my lab work. Now the work suddenly seems so easy.

[@brianhartmann5972]

Kahn academy is very helpful, in fact I watched this video to clarify some my knowledge on circuits because my physics teacher was unclear. However, in a battery, the electrons do in fact flow from the end known as "positive". This may be confusing at first but the reason that it is denoted this way is because that is the side with the higher electric potential energy (the side with all of the electrons, so it actually does flow from the positive end to the negative end). Other than that, this was a great video. I just wanted to clarify

[@gh-rb7bb]

thanks man I wish u were my physics teacher

[@tristanisgangsa]

THANK YOU FOR THE CLOSED CAPTIONS! :D It's great for hearing loss and to check if you miss something! :D

[@danoconnor4452]

I know this is 12 years old so you’re probably not going to read this, but what helps me understand that the current is constant is to think of electrons as cars and the circuit as the road. At each “resistor” in the road, the speed limit decreases by a certain amount. So the bottleneck of electrons is analogous to bad traffic. The main difference is that electrons don’t “travel” along the wire like a car travels on the road; meaning that the instant you turn on the circuit, the current is constant. You don’t have to wait for the electrons to “travel” to each resistor, creating a bottleneck and then having it slow all the previous electrons down (which is what happens in traffic).

[@poonamjoshi1101]

Man! Whoa Sal! 'If there is anything such as reality'-words of a legend (going through an existential crisis)

[@Mrs_Potential]

thank you very much. i totally have a different view on physics. its actually easier and more sensible than i thought. thank you

[@kabascoolr]

Lol I didn't know that he made videos on circuits. These, especially Kirchhoff's Laws really kicked my behind last semester. It's mostly because our professor was under the assumption that we knew circuits well before entering his class. I did but I'd forgotten most of the things.

[@aumgandhewar3114]

I love how y'all maintain retention by being friendly and sometimes amusing

[@hiyabalemayehu3443]

I know you guys think this guy is the best teacher but what I'm about to say is different THIS GUY JUST EXPLAINED THIS TO ME PERFECTLY, SOMETHING MY TEACHER COULDNT DO FOR A MONTH.

[@NoahA211]

I would honestly rather listen to these videos and just go to class on test days than having to sit through mundane class after mundane class...learning nothing. You are a life saver Khan!

[@madhusai220]

0:48, from that moment to this moment, i'm living in existential depression...

[@grigoriyefimovichrasputin7897]

I think its cool that really nothings real But dont worry bout it STRAW BERRY FEILDS FOREVER

[@Ray-tf2ps]

"when resistors in series we just add them up" YOU COULD'VE SAID THAT AT THE BEGINNING. But the explanation did help fix my curiosity

[@ScottLahteine]

I'm just starting on this path with electronics, so naturally I count on Khan to set me straight. But this is a little confusing as laid out. First, sure, label the battery output terminal + (as in, adding electrons here) but perhaps denote that the + terminal is negatively charged (neg.) because electrons are negatively charged. And just don't label the other terminal. Second, as I understand it resistors convert electrons into heat and radiate, so electrons are actually being spent by the circuit, and that is why the current drops. Correct me if I misunderstand this. Also, correct me if I'm wrong that: The potential difference (voltage) is the same across the entire series circuit, only the load is dropping, and smart DC power supplies will only feed the required amperes (for the given voltage) to power the circuit.

[@tonix1993]

Funny thing about the video is that in part 5:20 you say that electrons cant slow down just before the pass through the Ressistor.Thats not very right Well physics is so harmony that can allow that to happen xD think about it...if they slow down they compressed so they become a big minus charge in that area of the Circuit. Result? they slow down the upcoming electrons and in same time they push away on the other diraction the other electrons!!! Love physics ^^

[@warrencurrymetal]

18 people were amish

[@TimWhiteNC]

Sal is the Bob Ross of Science.

[@neurel111]

Electrons don't move across the circuit anywhere close to the speed of light. Their motion propagates at the speed of light. So when the first electron moves it takes the last electron to move as much time as it would take light from the first electron to reach the last electron across the circuit.

[@dhurbarajpuree2992]

This guy is so f*king genius. Love to learn from Khan academy. They are the gems.

[@mitch3850]

Sal is the guy talking, Khan is the academy he represents.

[@aniquanausheen7798]

i like this khan academy.. its awesome.

[@Tuanski]

I have a new religion called "Salmankhanism"

[@htmlfreak]

I believe total resistance in circuits are the following: In parallel circuits, the 1/R1 + 1/R2 = 1/RT (RT = Resistance Total) In series circuits, the total resistance is just the sum of all the individual resistors: thus R1 + R2 = RT Hope that helped.

[@sethboston6356]

You really have a way with teaching, as I am sure you have been told many times before. Thank you

[@abishekdahal403]

khan your voice is also a + point for your explanation

[@NitishChauhan1]

"if there's any such thing as reality" i've never seen a prof. get more specific when setting a premise.

[@hageraliart]

Could someone please tell me what exactly causes the potential drop when charges across a resistors?

[@DrLasker1]

thanks again sal! you mentioned a lot of small but important details which my physics teacher didn't mention (or perhaps I missed them because I was sleeping =), which really helped me understand this better! thanks!

[@dinoLomedico]

This gentleman is an excellent teacher !!!

[@poonamjoshi1101]

I don't want to become an electrical engineer, I just want to give my best in NSO exam

[@jorgediaz549]

I love this guy! circuits + comedy = priceless

[@bladervinay]

Ha ha 'Oh oh its my wife she will mind if i dont answer but anyway' Ohhhh you are brilliant Sal!!! Funny and brilliant

[@spilloholiker]

@69elchupacabra69 Electrons move very fast. But the reason the current moves so slow is that the way the current flows, is that one electron bumps into another. So imagine that in a tiny bit of wire there are 1000 electrons. The electron that comes into the wire bumps into the first one, that bumps into the second one, and it continues that way until it reaches electron number 1000. In all of that time it took these electron to bump into eachother, only 1 electron made it's way out of the wire.

[@Marsc0met]

@xDivineForYou @69elchupacabra69 electrons do flow very slowly. "For a typical metal, n = 10^28 m^-3, if the current is I A in a wire of cross-sectional area 10^-6 m^2 (a typical wire), we find v = 6 * 10^04 ms^-1. This is quite a LOW SPEED. If we turn on teh switch for the lights (5 m away), we certainly do not wait 139 min for the lights to come on! This is because , when the switch is turned on, an electric field is established within the wire. This happens close to the speed of light."

[@Hax04r]

@jaskaransingh because the battery is separated in a cathode(negative) and an anode(positive). There is a material between the two that has a higher resistance than the battery's voltage(basically the electrons are too weak to move through it). So the electrons can feel the force between the positive and negative terminals but they don't have the power to move. BUT when someone puts a wire between the two terminals(anode and cathode) the electrons can now move

[@rtsjoe]

I love it how he pauses to think how to put things in layman's terms.

[@Fmiguelify]

Thankj you, this video is really good, i undestand more about the series Circut now, and about the Volt Drops on the eacht resisters.

[@Physicsandmaths]

Yes, if the material is above its critical temperature it's not a superconductor.

[@WalterWipe]

10:02 we litterally both thought of the same numbers lol

[@WalkAbout28]

Sal has taught me math through calculus, organic chemistry, and now physics

[@GENEis1Wascally]

I liked the video. He is a very good instructor!

[@SaM0o0Na]

will after the first tow videos I felt more comfortable because I could understand something now. I will contenw watching them and I hope that I will get A on my upcoming MT.

[@Becca11Dance]

Is there any such thing as reality? That, my friend is a very good question.

[@alissajeanfreau7741]

I'm confused on how in the beginning, he said that the voltage is the same no matter where you measure, from at the end there being a difference in voltage from the beginning of the resistor to the end

[@atombarn223]

So your voltage will be the same when you put your meter from the positive and negative of your power supply OR the start R1 to the end of R3. Not in between each resistor. The Current (I) will be the same in between each resistor. To get your voltage in between each resistor you'll just take the current total and multiply it by the value of the resistor. Hope I was clear enough and this helps.

[@TheSantanu99]

"if there is any such thing as reality" 0:46 - Classic Sal

[@nileshpatil8665]

I didn't understand why the current is the same and why the total voltage is the sum of all the voltage drops. I don't like expiremental proofs that is why I am so confused. Pls answer

[@EldonSchoop]

@xDivineForYou, Well you are correct that electrons flow faster than a few inches per hour (!), remember that electrons are pushing on other electrons in the cable, and the light would turn on almost instantly anyway. Think of it like a hose full of water that is just turned on. Of course the flow of the water isn't terribly fast, but the water that is currently in the hose is pushed out immediately, causing a seemingly instantaneous flow of water. Same deal with electrons. :)

[@BaronMorte]

Sal,you are the man. Thank you.

[@kelvinmann7993]

I'm honestly just learning this so I can make circuit boards for music boxes. My brain is gonna hate me

[@devigopalakrishnan2909]

This video is great!!!

[@actionjessie]

lol at "if there is such a thing as reality"..

[@kamikrazi123]

How is this guy so damn smart??

[@chainheart3]

tanks! this video is awesome!

[@SanFranLOVER1972]

I love you. Seriously. MUCHO LOVE FROM GEORGIA IS BEING SENT YOUR WAAAAAAAAAAAAY!

[@Alapozo]

This was a very good video!!! Great explanations

[@comedian619]

Very Helpful.Thank you

[@sharkbaitoohhaha2341]

If Sal ever has kids, they will be all-knowing!!

[@kikibarrios]

Internet is full of info about almost everything. Search on google for : How fast do electrons move? I hope that helps.

[@vedatbajraktari5806]

Nice job. Really im a university student but there in class is so boring and rabish lecture. Thank u, we looking forward to see more videos.

[@dulanherath5927]

Best explanation👍

[@TareqKhan0]

A correction at 4:55. Electrons do not move at the speed of light through copper wire. Inside the wires, electron moves very, very slowly, almost as slowly as the minute hand on a clock. Electric current is like slowly flowing water inside a hose. Very slow, so perhaps a flow of syrup. Read more: amasci.com/miscon/speed.html

[@danielking7100]

this video changed my life

[@sphericalcow4004]

Same bro

[@danielking7100]

dude who are you?

[@sphericalcow4004]

it's a me. mario

[@leenapatade2582]

Video and explanation is too good but it was a little bit difficult to understand. The speaker here should speak more clearly. If the speech isn't clear the listners won't be able to understand what the good is speaker wants to deliver. Pls pay a kind attention to it. A kind advice😊 Thank you for all ur videos ! Excellent videos for the betterment of students. Thanks guys !

[@jake_runs_the_world]

why dont the electrons just get to the +ve side through the battery , why all the way long and then ?

[@kimballchoo]

That's what you get for camping!!

[@GymMusicAddict]

@arkdude211 Me too! I swear my teacher doesn't understand physics. Today, my class decided that this girl in our class knows more physics than our teacher does. :D Watching this video (and part 1) and writing notes on them was my physics homework tonight. Thank god! Khan, you saved my life, I think I'm starting to really understand this concept now. :)

[@tadm123]

I have a question is the Current always constant everywhere on the circuit? or just in the cable not going through resistors?

[@nana_smallmango]

I love Khan Academy

[@KarishmaGReddy]

great video!! thanks so much

[@techmaster90]

This is great thank you!

[@adsalazar12]

When you say that the current is constant throughout the circuit, does that only apply for resistors in series or also in parallel? Is it constant always?

[@skyewalker123]

@naznazi89xxx (dumb name btw), series has same current (I), as when it is in parallel it is the same voltage (V). this video is just series, go on wikipedia if you do not understand the difference...

[@sathibabu9365]

Sir according to the ohms law V=IR voltage is directly proportional to voltage so there is voltage drop in circuit due to adding resistors but current is constant through out the circuit why ?

[@liamlovespie]

@nilanjana96 Yup, you are right. but an electron doesn't have to travel all the way through the wire from neg- to the pos+ terminal. Its like water in the home. You dont have to wait for the water to travel to the tap, because it already present. Same with Electrons. Electrons already in the wire near the other terminal flow out. (I said the same thing as you, just simpler and better spelt. You appear to be a smart guy and know your stuff, so why is spelling such an issue for you?)

[@Physicsandmaths]

Hey Sal, You said no wires without resistivity exist. Well, superconductors don't have any! They have a resistance of absolute zero.

[@knguyen542]

Would electrons not bunch up due to "like charges"? Thank you this video helped a lot.

[@_underrated_dre_]

So will the total resistance or actually the way of funding the total resistance be the same for a parallel circuit?

[@NilanjanaLodh]

@liamlovespie i accept it! :) this is well spelled and easier to understand than my version... sorry for the quarreling.. :)

[@mini-337]

Thank you sir

[@viktorgoa]

yes, they travel slowly. The reason why its fast, that its going in waves

[@nikkil3631]

But according to Ohm's law current is directly proportional to the potential difference. So when the potential difference decreases shouldn't the current also decrease along the circuit. How can it remain constant?

[@user-dv8we9kq5c]

i've learned that electron in a circuit cannot move at the rate of light. a lot of electrons in conductor just move at the same time when pushing the electric force. Im confused in that point.. i want to know the theory accurately