Circuits (part 2)

[andrizee91]

I love how gentle his voice is! (no homo)

[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.

[ShadowCloud143]

You will see me in the next video.

[SanFranLOVER1972]

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

[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

[Shinnosuki]

so if you actually have a crap load of resistors, it makes me think of a portable heater, which makes sense as they cram so much electrons into it that makes it heat up and thus it gets fan off...same principle?

[TheUsaidkhan]

lol whenever starting an example you say, "so lets say that the voltage is... i dunnoe.. 20V"

[kschwab14]

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

haha love the dedication

[kourosh89]

Wouldn't the electrons accelerate after the third resistor?

[actionjessie]

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

[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...

[JesusCanez42]

If there is any such thing as reality. LOL, classic Khan.

[Crow12666]

I just wanted to kmow how to make an usb powered fan lol

[11031992em]

sir, do you have "wye, delta" circuit analysis examples?,

[dinoLomedico]

This gentleman is an excellent teacher !!!

[DaniellaRox123]

thumbs up if u thought about star wars when he said "r2" =D

[pufixas]

@DaniellaRox123

I never watched star wars

[gychang00]

thank u, excellent

[narutosramenbuddy]

thank you for saving my soul AKA my GPA.

[lazer1235]

Good now what about parallel circuits

[Naznazi89xxx]

PLEASE REPLY ASP

in my text book, it says that " resistors in parallel all have the same potential difference" and " resistors in series all have the same current" and Khan said that in series V is the same everywhere tooo... am confused?

[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.

[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!

[kamikrazi123]

How is this guy so damn smart??

[miger224]

Thank you for ignoring your wife in an effort to help us lol. Makes me even more thankful XD

[tadm123]

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

[lopta33]

Could you please explain a little better how does a voltage drop thing work. The electrons being eager to get somewhere, and being tired of bumping just sounds kinda not scientific xD

thank you :)

[datCRUNKbuay]

Can someone please explain 00:47? What does khan mean "if there is a such thing as reality"?

[hendsem]

@datCRUNKbuay it just meant he watched The Matrix and Inception :)

[123IN321OUT]

@datCRUNKbuay He's probably a follower of Eastern Philosophy. LOL. I like this video however.

[tadm123]

@datCRUNKbuay its just philosophy, just random theories and ideas

[supermanXL]

you are a great teacher

[rtsjoe]

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

[Sconz32]

What goddam playlist is this?

[bobojoto]

Wow. This cleared up so much for me! Thank you for putting up these videos! They really help. :)

[eugk321]

You are simply amazing. This whole lecture is exactly what i need. I like how u don't miss anything such as "voltage drop" and all the conceptual ideas.

[QuantumCoulomb]

thanks alot for your videos!!

[kliao93]

thank you for the vid, btw i loled so hard 3:30 . you sounded so mad haha

[ASHLEYis1sweetbaby]

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

[CryatainTribe]

is there really a such thing as a perfect conductor ?

[kadajett]

@CryatainTribe Nope, not that is known to man. But I am sure some things can get close. Cheers :)

[j4rko]

@CryatainTribe Actually there is. See Superconductivity article on Wikipedia for more information.

[rayd89]

any normal conductor at absolute zero

[freezingbeast]

@rayd89

Absolute zero... Which is both theoretically and practically impossible to reach.

[papag000]

YOU SOUND JUST LIKE REGGIE MILLER

[BaronMorte]

Sal,you are the man. Thank you.

[69elchupacabra69]

Don't electrons flow very slowly? I mean like a few inches per hour?

PS: Please don't thumb comments(including this one) just because it tries to clarify some things by asking. It would be better if people just answer or ignore it.

[kikibarrios]

Internet is full of info about almost everything.

Search on google for :

How fast do electrons move?

I hope that helps.

[69elchupacabra69]

Yeah, and it said the same. 8cm/hour in one site. I just heard khan say it travels at the speed of light so it made me question my understanding.

Thanks for the response though :)

[viktorgoa]

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

[jman7152]

No, electrons move extremely fast.

However, in something such as an AC current the net movement of a single electron is small over time.

[kiwiki]

I don't know why this is thumbed down. It's quite true. If you think of electrons as small particles of mass they're essentially moving really fast and "bouncing" around inside of the wire. This isn't the most efficient way to move "forward" so net movement is slow.

[kiwiki]

The reason why appliances turn on so quickly is that there are so many electrons in the wire it's not like you're waiting on one electron to make its way from one end to the other...

[Ganstasmurf]

@69elchupacabra69: Electron's flow very fast (in a vacuum); depending on resistance. For example: if you sprayed perfume in a closed in area, you would smell it immediately; if you sprayed it outside where air is resistance, and the electrons have collisions, it would be slower than fast (10^n) where n is a large number.

[cmxcmx]

@Ganstasmurf no, kiwiki has the right answer: the wires etc where the electrons are flowing through start out with a neutral charge; meaning they're pretty much saturated with electrons. think of this like a long hose that's already filled with water: even if the water flows slowly, the other end of the hose will begin spouting almost immediately.

In a vacuum, electrons can flow very fast, but still "only" about 1/10th of the speed of light. in a circuit, it's only a few cm per minute.

[viptutorialscom]

Yes and no. Depends on the current type you are talking about. DC current is flow of electrons, whereas in AC current e- transfer the energy in form of vibrations (back and forth), and here they are stationary.

Either way, the speed of e- in a wire is dependant on several factors. We know that I=(Q/t), therefore in order to increase the speed of e- flow you have to increase the current (more Amps, e- move faster). Also the thiner the wire is the faster the current flows. :)

[xDivineForYou]

@69elchupacabra69 You plug something into a socket and turn how the switch. It almost turns on immediately right? so if electrons flow so slowly as you said, it would take ages to on a appliance!

[zinodikudu]

@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. :)

[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."

[MopDMTBARTL]

@69elchupacabra69 - i'm just thinking here, maybe that is a made up explanation that provide to support the 'conventional theory' taught in school that the flow is positive to negative when in reality it's the opposite. just a hunch.

truthknowledge. com

[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.

[hannu1996]

@69elchupacabra69 yeah the drift velocity vd = I / neA

where vd=drift velocity

I = the current

n = charge per unit volume

A = cross sectional area

e = 1.9 x 10^19 C

[nilanjana96]

@69elchupacabra69 yup, u r rit. bt actually,an electron doesnt hv to travel all d way thru d wire frm d negative 2 d + terminal.d flow of electrons is actually like d flow of water in our homes.when u turn on ur tap u dont have to wait till d water frm d overhead tank flows all d way thru d pipes in2 ur tap.d water flow jus starts instntly becoz d watr which is already present in d pipe jus flows out. same is d case with electrons.d electrons already in d wire near d othr terminal flow out.

[nilanjana96]

@liamlovespie oh! u r a spell-bee i guess? that is why u spell talk as tork?anyway, the answer was a bit too lengthy so i had to use message language..

now if that is what u call "horrible grammar" ,may be u should acquaint yourself with some basic IM language.

[liamlovespie]

@nilanjana96 I R NO SPELL-BEE! U R M33N! Seriously bro? Are you mentally disabled? I know its "IM Language", but it frustrates me to see it used. It should have died in the ninetys. Nobody actually talks like that. And i know how to spell "talk". I was emulating you. Learn to spell, or don't say it at all. "Rit", when said IRL, doesn't even sound like "Right". It sounds like "rit". Also capital letters at the start of each sentence and spacing between your next sentence and your full stops. Out

[nilanjana96]

okay, i know that what i wrote was a little unreadable, but let me tell you that a you-tube comment can have only 500 characters and i tried as hard as i could to fit my answer into one comment. now if you can write better than this, well then! write the exactly same thing with perfect grammar rules and delete my one.

[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?)

[nilanjana96]

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

[Kosekans]

I feel forced to say that the deadly level of current is not at 1 Amp, but at 50 mAmps. All GFCI built today switch off at that level.

[uselessfaith]

"maybe they're just tired of bumping around so much" lol

[devin1694]

voltage is contant in a parallel circuit and current is constant in a series circuit right?

[planetdarwin]

Why do people say more than an amp can kill, when mathematically I could connect a 9volt battery to a circuit with a 1ohm resistor, and have a current (I) in the circuit of 9 amps, but when I touch it with my finger obviously I don't die. I don't even feel it. Is this because the voltage is relatively low, and if so, does it mean the old advice about the danger of amps should include a sidenote about volts as well?

[jewtubeistehsuck]

I don't think you're taking in account the resistance of own your skin and body.

[planetdarwin]

Good point.

[diademonster]

your skin has alot of resistance which would probably lower the current quite significantly

[JESUSSDAD]

just for fun . letets throw in another resistor ......... lmfao bro.

[vipersinu2]

E/R = I

you said 20 X 10 is 2 shouldn't that 200

[zvolencan77]

so ..V is the same everywhere but ends of the R's depending on how big drop they cause (20V)???Then Current is the same (2A) everywhere but inside the R's ???

[zvolencan77]

well now i think i'm wrong..or not ?....but you said that voltage is the same across the wire or circuit in the beginning of the video ?!?! But can not be the same at the ends or "inside" of the resistors..correct?

[zvolencan77]

Am I correct khanacademy ? Greetings from Slovakia...very good videos...thanks

[MisanthropicDolphin]

Ok, so the current is constant through-out the circuit, but the voltage isnt? (V1, V2 & V3 are different?)

[zvolencan77]

Yes..that's how i understand it....when the electrons leave the resistor they become "normal" again ...it's like they remember they former objective so their "will" or technically voltage is the same everywhere other than inside the resistors.I imagine resistor as a chamber where the electrons get high or gassed and forget about what they where up to so they lose their will :):)That is why measured voltage or "will" inside or on the ends of the resistors is different depending onhowmuchgasis in

[calvinhobbesliker2]

don't the electrons experience a voltage drop when travelling through the wires and not through a resistor?

[hacksign000]

the wires also have resistance :)

[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)

[Physicsandmaths]

Hey Sal,

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

[blazekid1992]

all the materials have resistivity, superconductors are only made when they are cooled down initially they have some resistivity

[Physicsandmaths]

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

[cfhforever]

if we know that the current goes from negative to postive, why are you drawing the arrows of the current going from positive to negative?

why don;t you just do it from negative to positive?

[i3loodhunte31181]

because that people who first discoved this stuff made it pos to neg. there is no other reason.... no one knows.

[gangstasal85]

doesnt matter either way, doesnt affect math or intuition of it

[Vyraji]

wasn't voltage letter U instead of V?

[mahivell]

LOL, your wife's calling and you didnt pick up.

anyway, you should replace my old and naggy physics teacher.

you're way better, dude.

[geminiflux0]

haha "if there is any such thing as reality..." yeah...

but at least you exist even if only as a thinking thing

[tomboy149]

lol thx haha ur wife calling

[adow010]

thanks

[adow010]

pliz i would like u to review the difference between series with resistance and parallel with resistance

[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.

[takity]

great videos!

[KarishmaGReddy]

great video!! thanks so much