Kirchhoff's voltage law | Circuit analysis | Electrical engineering | Khan Academy

[@hossboi52]

ATTENTION: EVERYONE WHO IS ASKING ABOUT -20 VOLTS.... His equation Vrise - V drop = 0 is the equation for the whole circuit. On the left side, where the battery is, there is a 10V rise....on the right, where the resistor is, there is a 10V Drop...this is where he is getting 10(rise)-10(drop)=0 | That rise= -10 is, like he said, just another way of writing a drop. I understand the confusion, there is not much point of writing that unless he wrote 0=sum of voltage rise ... in which case that specific "rise" on the right would technically be negative due to the resistor, however that is often confusing and he just was using this as a way to get you to understand that this is a decrease in voltage. His math however is all correct.

[@mstfarzanaakther8046]

Thanks a lot

[@Rick-gd6pe]

By any chance do you know what the voltage is actually doing when it drops?

[@brandonbennett4970]

@@Rick-gd6pe the potential energy between individual electrons in the wire is dropping, meaning they are getting further apart. Because energy should be conserved in an isolated system consiting of the wires and resistive element, the loss in potential energy presents itself as an increase in heat (or light). This is a vast oversimplification of what actually occurs on the subatomic level and is not totally correct but it is a great way to think about it when first getting started, and will take you pretty far in electronics.

[@L28PriyankarDas]

@@brandonbennett4970 If the distance between two electrons is increasing, the potential energy of the system decreases overall,but why doesn't the energy comes off as kinetic energy? I mean shouldn't the speed of electrons in the system increase?

[@brandonbennett4970]

@@L28PriyankarDasthe electrons collide with resistive material and lose energy. They don’t get a chance to increase their kinetic energy because it is lost as heat

[@lihlezonela6377]

khan academy is the legendary site my boy

[@dannewlon5825]

Great review, had all this 40 years ago in college, but basics are always applicable.

[@jasssa8635]

the voltage directions are wrong so the numbers become wrong too. this is very misleading

[@mahshidpanah8851]

Voltage drops across the components (resistors) are positive if a loop direction is opposite to the current direction

[@arfairfan9870]

Thanks a lot

[@samriddhi0906]

thankyou!❤

[@curtpiazza1688]

Beautiful! 🎉 😅😊

[@JustinHatter]

Thanks for the help!

[@abdeslamkabiri9392]

-10-10=-20

[@gouenjigouenji7126]

Good eyes.

[@abdeslamkabiri9392]

:)

[@fatimaafaf5740]

exactly!!

[@abdeslamkabiri9392]

;)

[@pn2696]

I had that question too😏😏

[@wisnuaimariyadi840]

far way better

[@stevenroberts3148]

QUESTION: I thought that the voltage throughout a circuit was constant. I'm confused by the whole "voltage drop" thing. Shouldn't it be constant through and after hitting the resistor?

[@raheelbelal5848]

in series it drops, but in parallel it stays the same

[@smgf-dm3zu]

No

[@demonslayerer]

I ain't no expert but from my understanding of volt, volt is just energy applied on charge to overcome the "opposing force" (Resistance). Or in other words force to get charges moving but force will be zero if there is no Resistance or charges are already moving, therefore if Resistance is zero either volt is zero (meaning charge need no force to overcome Resistance since it's already zero) or the current is infinite (which again means the same but this time it specifies that charges ARE moving).Resistance causes voltage causes current. So answer to your question, voltage isn't constant. (Correct me plz if I am wrong in anyway, i highly appreciate it.)

[@L28PriyankarDas]

@@demonslayerer sadly you are not completely correct,Your relation between resistance and volt(potential diff) is accurate,but in no way volt is energy required to overcome opposing force.Honestly i can not explain it here in the comments.

[@snakes-and-ladders]

Voltage is the energy per unit of charge. As charged particles pass through the components of a circuit, they will transfer energy to them. This results in a voltage drop.

[@PatrickMoto97]

Thanks bro

[@RR-ex2uv]

Thank you so much for this video! I have been really struggling with understanding when voltage and amp sources are equated as being negative verses positive, especially when there is a mix of both in the circuit!

[@alexjag5778]

Thank you

[@michaelpiotto4988]

voltage rise is not -10V, that make no sense. It drops 10V and then it drops again -10V. or it drops 10v and rises 10v.

[@MOHTAHA2008]

I did understand the concept, but I do have a question tho, does kerchhoff’s law mean that (theoretically) the delta V in every closed series circuit is equal to zero?

[@steventodd5884]

Yes because they will all cancel eachother out. The net change would just be zero.

[@chandhnichowdhry2811]

Thank you... It was very helpful 😊

[@leetcoder1159]

really?

[@aboringuy]

Great video! Just one question: Will running two 12V fans in series off of a 24V power supply overvolt the fans? Or does the voltage have nothing to do with this equation?

[@ChocoBaiterEUW]

has nothing to with that. do 12v to both.

[@yahyamohammed6729]

It makes sense that it's 5 volts in the middle node, but how do you get to 5V? Mathematically speaking

[@СщькфвуЫефдшт]

You can look at each resistor as a voltage drop. In this case 10 V between 2 resistors drops by 5 each time.

[@andycoutts517]

@@СщькфвуЫефдшт But why does 200ohms create a 5volt drop?

[@alex3l4]

​@@andycoutts517since the two resistors are connected in series, you can calculate the resultant resistance (R1+R2=200) and using Ohm's law (I = U/R = 0.05 A), calculate voltage drop by (U = R*I = 0.05*100 = 5 V)

[@unknown-vq1gj]

If drop is 10 volts and rise is -10 volts. Formula V rise - V drop = 0; in this case -10 (rise) - (+10) drop= -20?

[@harryiii3361]

Those two values are referring to what is happening at the resistor, not the whole circuit. He was only pointing out that a drop of 10V is exactly the same thing as a rise in -10V

[@medhatithidas5063]

10 volt drop is same as -10 volt rise and you can also say that 10 volt rise is same as -10 volt drop. If you cosider it like this and the formula is that Rise - Drop =0 Then -10 - (-10) = -10 +10 = 0 Here I have considered 10 Rise as -10 drop and 10 drop as -10 Rise. It is quite confusing though but yes this is also a way how it works.

[@JamesDean-wv7iw]

Sort of made sense to me, how I am suppose to get my head around KIV and KCL, I have no idea

[@deepakkr.773]

Good

[@aselim20.]

I wrote it

[@jwilham]

you need to explain why you are going from 10 volts to 0, and why you are going from 10 to 5 to 0. how unnecessarily complicated trying to explain rise with decrease of voltage.

[@hafizulsedutrik]

কে কে মেডিকোর বই দেখে আসছো?

[@subhashkale2654]

This is the most disappointing video of khan academy...... 😢😢😢😢😢

[@talibqadri6403]

exactly

[@archivvithlani6610]

it's such an easy topic?

[@physicsclassofshamimsir8329]

Ure being disappointing

[@steveevets1130]

"I'm going to arbitrarily call this 0 volts". Why? Ohms law says that the voltage there will be .05V. Is that not correct?

[@akshatshah3925]

0.05A is the current, not the voltage.

[@mahes9263]

Can someone give me a proof why the voltage drop should be the same as the battery?

[@roycekimmel]

The potential energy is exhausted over the path of the circuit much like lifting an object off the ground to increase it's potential then dropping it only for it to return to it's original potential (converting potential into kinetic energy for example)

[@insajderpapaj4650]

So complicated explanation of a sumple thing

[@Inaflap]

@4:30 you suddenly changed the term from voltage drop to voltage fall. Otherwise this was a good video.

[@gouenjigouenji7126]

It's the same.

[@gouenjigouenji7126]

It's not a flaw

[@hunterhunter109]

This video is really informative unlike half of those Indian videos which one can't even understand the language

[@3lxlDeMonlxl1]

excellent video how do you do it?

[@Tom-gc8ik]

Ok. Why did you "arbitrarily" name nodes with negative voltages? Is it with respect of the voltage in? And why does -10-10=0? Why is the node between the 2 resistors 5 ohms? Why does the voltage rise and drop in a circuit after sal showed its uniform all the way around? These are things that should be addressed. Instead of just saying this is it, you should leave the viewer with the knowledge of why this works and why it's useful. No intuition developed from any of your videos. I'm sorry. I'm sure you're a brilliant engineer, but when it comes to conveying your knowledge/intuition on a subject, not very good. Thanks for the effort though

[@omega6872]

That was the best way to put it !

[@ombatra1000]

That -10 is just to indicate direction .

[@MyrahOfficial]

Bruhh dude it was so easy and awesome ... honestly u just read once from a book, come back to it and then you'll see its fab

[@_aidid]

(For 2:19) If I connect one voltmetre across the battery and another voltmeter across the resistor will the voltmeter across the battery show +10V and the voltmeter across resistor show -10V ?

[@СщькфвуЫефдшт]

To clerify, the rise isn't a - based on the equation you followed? There's some conflicting values confusing me...

[@pooffdk]

you can do one thing here and just use the clockwise technic it will be less complicated for you

[@parasonu1]

what happens when charges move flat I mean why does potential drop occurs only at resistors? I mean when an electron travels from negative end towards the positive end it continuously loses potential so why we don't consider potential at flat areas where no resistors are present ?

[@sherllymentalism4756]

VIKRAM SHARMA it's very low so we usually ignore it. Not always, however

[@roycekimmel]

That is covered in resistivity though for circuit design is often negligible

[@ZollMisc-c1w]

Thompson Jose Perez David Garcia Kenneth

[@worldofmusic1058]

I am a 13 yr old watching it so it is a bit difficult for me to understand this. Can you guys please help me at this?

[@robbydiaz4922]

yeah so what's your problem

[@ajaykumarray8925]

First grow upp

[@sebp400]

he's calling branches, nodes? I'm learning and it's confusing.

[@hasibullah3902]

Y u no discuss complex circuits??I get stuck in the maths given in my book

[@mohitchahal9476]

couldn't understand...

[@lihlezonela6377]

ever had of LOGIC gate ntwana yam?

[@dilkashaikh]

how to download physics playlist lecture in one times please tell me the procedure or name of software i want to all playlist videos in one times thank you

[@swapnilg.5996]

Khan Academy App

[@yawarkhan8309]

Rise negative so_10_10=20 why u write 0

[@HTCRAZYKWA]

So does it always work in a manner that 100 ohms is always one tenth of the or is that just an example for the current equation

[@pamelabosworth433]

Martin Margaret Robinson Paul Anderson Barbara

[@chriswoolson7352]

This video was totally not correct. With different resistances, it is totally different

[@IbnMeer786]

why we taken conventional current +ev to _ev??

[@jebeccajamil]

although we know that electrons flow from -ve to +ve, conventional current is followed because by it makes the calculations much easier.

[@chaddonschaddons7084]

Pretty badly explained because 'rise' has nothing to do with the perception of view, it has to do with the travel of conventional flow. Just to further prove this, imagine the resistor is sideways, left to right instead of up and down. There is still a drop on that resistor even though it's going sideways. The problem with this instructors explanation is that he is inferring that voltage is a sort of travel, but it is not gradual travel, it is explicitly a measure of the difference between two points. Here's where this video fails and it is the problem with the conveyance of the teaching.

[@CarnegieDorothy]

Lee Angela Perez Mary Johnson Lisa

[@TheRoxas13th]

Why the voltage drops?

[@salunkhesaurabh201]

TheRoxas13th Volts is the difference of potential at two point ... so in battery we consider (-ve) as (0)volt and (+ve) as (V)volts

[@loneventhorizon]

it didn't the current flows from - to +

[@loneventhorizon]

america vs everyone else

[@danieljoseph6404]

because the total voltage in the circuit is 0 and theres only one resistor. so after it passes the resistor it would be 0.

[@vomont]

Daniel Joseph what if there is no resistor. What happens then?

[@dinsrock1]

Hey, in 3:03 there is a error is guess, look, u have taken voltage rise as -10 and voltage drop as +10. The formula u told is saying voltage rise minus voltage drop=0 . If i substitute that " minus 10 minus 10 which leads to -20. Can u xplain on this.

[@surajphaniharam8734]

Actually the rise is 10, look when it passes through volt meter and the drop is 10 as he said so that implies 10-10 which gives you 0 👍

[@aizasaed170]

where the hell has sal gone😟😟

[@TheAlexsennin]

Aiza Saed 😢

[@MyrahOfficial]

Ikrrr

[@blessyie643]

I hate math

[@mohan4431]

why

[@Cloudfights]

💯💯💯💯

[@hand_make_art]

Sorry but this is very hard

[@julianzzip3929]

Second

[@ethank.4103]

Why does he sound like Jonah Hill

[@विसाजीदेशमुख]

bharat mata ki jai

[@mr.osx3423]

To hell

[@mustache2295]

Very useless.