Parallel RC circuit

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Physics Ninja looks at an RC circuit where the Resistor and Capacitor are in parallel. The current through each branch is calculated and limiting cases are examined.

[@mrgoodvibs3742]

So true. Nothing in my text book about capacitor in series with resistor but it doesn't stop my teacher from putting it in an exam. And he never showed us this case but expected us to know it.

[@whatever3041]

There are infinite possibilities with circuits, your teacher can’t show you every possibility.

[@sarahholland5980]

There was a question like this on our practice exam but we've never been taught how to work through RC circuits, much less how to work through parallel RC circuits. You are incredible, thank you.

[@gammafirion9162]

You know those nasty little mundane, seemingly simple “what if” physics questions you think about but can’t seem to solve... You just helped me out here bro appreciate it!!

[@mikeoxlong2077]

i know that feeling

[@GuitarlordJohnBurton]

I'm 1:03 mins into this and I already want to say thanks.

[@PhysicsNinja]

Thanks, hopefully it gets better.

[@MarkSmith-vo1vn]

@@PhysicsNinja For the circuit at 5:48 why doesn’t it short circuit?. Like wouldn’t the electrons be attracted to the positive terminal of the compassior?

[@icedem0n326]

Your first two minute perfectly explains why I'm here.

[@keenanwyatt7929]

The textbook “electrochemical methods” uses this circuit to describe electrochemical cells. R1 is solution resistance, R2 is charge transfer resistance and C is called the electrochemical double layer capacitance.

[@MrHigoli]

the best explanation about this topic. thx a lot sir!

[@ajax3375]

Sir,such an amazing explanation. I also encountered such a problem in my IIT JEE entrance examination in India but unfortunately couldn't solve it but now planning to sit for it again. Please keep uploading such problems sir.😃😃😃🙏🙏🙏🙏🙏

[@brentbarnhart5827]

In 1 of those books, maybe it will explain that your volume on this video is so LOW, that when I turn it UP, and forget that I did, when I go to the NEXT, video, the books will probably tell you I will JUMP, and hit my head, along with deafness.

[@taqiyaehsan3522]

you just got so many blessings for posting this video

[@kestonsmith1354]

lecturers shouldn't be paid , this guy should. he gets to the point with detail. Lecturers read notes from a powerpoint and cant explain certain things but they have a DR in front their name.

[@roxymigurdia1]

why lectuers shouldn't be paid? lol

[@jamesonthomas9583]

Thanks, I’m gonna try to expand this to calculate the time of each interval on an astable multivibrator

[@yusufkeskinoz9740]

You sure deserve more likes sir. Saved my life

[@PeterSHollander]

Wonderful explanation! I was able to follow along with a similar circuit (where R1 is placed after R2) very easily. Now to figure out the equations for discharging! :)

[@user-zm3jd7pr8o]

I'd like to repeat my favorite comment I've seen here: So true. Nothing in my text book about capacitor in series with resistor but it doesn't stop my teacher from putting it in an exam. And he never showed us this case but expected us to know it.

[@kina4288]

This is so helpful and not tedious in its derivation. I would not have been able to analyse the energy consumed or stored by the different components including the energy . Cannot thank you enough.

[@brosephus_rex1374]

Just want to let you know that you are a hero!

[@fatimamohammed586]

I am doing University Physics with Modern Physics by Bauer and Westfall but it is published by McGraw Hill Education (Have you heard of it before?). All I can say is that there is no discussion of it there either, but it is all over the problem section and concept checks and all that.

[@danielkwon3062]

OMG I finally found a true real actual professor

[@seriouscat2231]

I see that he basically knows what he is talking about. But I find it difficult to follow this because I find it hard to tell what is the actual gist of what he is doing, and what is just one way of doing it. This is like getting your ass kicked. You know that in the end you will be sore. You know when it starts and when it is happening. Then you suddenly realize that "hey, I made it" or "hey, he made it". I do not suggest he'd do it using clearly numbered steps, but I suggest that the viewer should get an idea that such structure exists. That he simply not call something a "method" and then just dive in, but that an average person could see that yeah, that is a method. Or maybe I need to watch it a few more times?

[@SevalUzunal]

Thank you for explaining how "really parallel capacitor" works.Not easy to be sure, for example, while capacitor is charging whether current flows on other branches. All I've seen so far, even in the most famous books, the most simplist circuits. Your example is the only one , have a closed loop "closer" to the voltage source than capacitor. I could see no explanation about the behaviour and calculations (current flow , voltage change in all branches,...) during major phase like charching, discharging neither for DC nor AC .... They usually supply all maths, equations,time dependency...

[@braedenlarson9122]

Thank youuuuuuu, literally helped me out with a problem set I am working on so much to conceptualize!

[@jbangz2023]

Great video, I have used in my IC leakage test analysis.

[@benjamincordes207]

Thanks a lot, really clear and detailed explanations!

[@umairlari1498]

U went through all the books! I got this type of question in my coaching test, I came here for solution

[@muratkaplan669]

I can't describe how i am grateful Thank you

[@nutboy2676]

You deserve 100 likes and a cookie

[@blackhatgaming5497]

Hi! I have a doubt. What will be the effect if I attach a variable capacitor parallel to the resistor. I hope you answer my doubt as I am 3 years late.....

[@normancorbett9488]

Great video. I am a mathematician but hobbyist in electronics. Nice to finally see some connections. What happens when R1=0?

[@alonewanderer4697]

Then the charging up of the capacitor happens infinitely fast (of course in practice that’s impossible) and the voltage across R2 and C becomes equal to the voltage of the source. Then the current only flows through R2.

[@bobbypesch5220]

I find it funny how this problem can't be found in all those textbooks but its the first problem on my next hw. Man i love georgia tech

[@rohangadgil4527]

Such problems can also be solved by a method of COMPLEX NUMBERS It is teached in highschool in India usually in JEE tutorials

[@PhysicsNinja]

There are many ways to crack an egg. Before learning the shortcuts it's more important to understand the basic laws and learn how to apply them because they always work.

[@fizixx]

Your sound level is always low. Any other y-tuber has the sound about the same. Love your vids, but I can hardly hear you on a mobile and on my PC at least I can boost the volume more, but keep up the great vids......always enlightening.

[@stephenfulmer1910]

I actually had this problem on my hw for my physics 2 course at ULL

[@allisonsnyder2998]

This was very helpful, thank you.

[@michaeldrake2512]

Similar question on my 1st year basic electronics assignment, except R2 is in series with the capacitor, all I have though is the formulas for discharging and charging, but none of those are working out to be correct or measuring the same as the circuit simulator I'm using. Afraid this level of maths is also beyond me at this point. Electronics is not for those without patience or persistence

[@sidb6471]

great video dude, just like you said, I couldn't find it anywhere it else

[@benmillar04]

I'm a bit rusty on my calculus, but checking the integral w.r.t. Q given at 17:38 in the video, shouldn't the integral of dQ/(Q - a) = ln(Q - a) for any constant a?

[@kumbongstanleyyoh2746]

You are really great sir. Thank you so much

[@MikahJabrowski]

Delmars Standard textbook of Electricity is where you’ll find this

[@seriouscat2231]

What was the actual time constant in this? My entire reason for watching this video was to see you isolate it. I could finally guess it was (r1 * C) over alpha. Also, I found most of what you did impossible to follow since I am not fluent in rotating equations. And I guess I will never learn to be, because nobody ever stops to show how it is done. Everyone just expects everyone to already know how to do it. It would help if you'd simply say aloud what are you dividing or multiplying where.

[@seriouscat2231]

@SharkTank, I eventually solved it by repeatedly applying Thevenin's theorem.

[@seriouscat2231]

@SharkTank, what algorithm? I thought you get the decay rate using a simple formula.

[@steveying1305]

fantastic, you are so explorative

[@1234Tubie]

I think there is a better or easier way to solve the currents in terms of the Laplace transform or complex Z

[@dylanpene1638]

Thanx you very very much... i too i looked for it everywhere... vielen Dank

[@PhysicsNinja]

Dylan Pene thanks for the comment. I love student requests!! If you’re struggling with physics feel free to reach out.

[@asaadalalawi3561]

and when calculating the time constant, shouldn't the equivalent resistor be R1*R2/(R1+R2)?

[@PhysicsNinja]

asaad alalawi yes, check out my other video using thevenin equivalent.

[@PhysicsNinja]

asaad alalawi that’s what you get if you simplify my expression with alpha. If R1 is 0 the capacitor would instantly have voltage V so initial current is infinite.

[@asaadalalawi3561]

@@PhysicsNinja Thank you, just wanted to make sure that i'm getting this right. Thanks!

[@hardikraj3175]

Really helped.thanks Very clear explanation

[@dreamliver750]

what a beatdown lol

[@haocheng7074]

your video save my life!

[@aelu4194]

Thanks a lot, I assumed that V = Vc after full charge (like in a simple RC) and got into much confusion.

[@ravioliformuoli520]

Can you do this same circuit, but instead find the transfer function as well as cutoff frequency?

[@amiyancandol4499]

What if R1 is not there? Only R2 and C1 in parallel, I think I read somewhere that it will get instantly charged

[@PhysicsNinja]

Yes, c1 is instantly charged, and current will run through R2. All branches of a parallel circuit have the same voltage across them.

[@amiyancandol4499]

@@PhysicsNinja thank you so much didn't expect such a fast reply!

[@pedrovinicius3621]

Wait, why i2=0? How the cicuit is shorted to gnd without electrons passing through

[@marioedgardocarias91]

What change if the capacitor already had previous charge and the voltaje at T=0 is not cero because in time before cero it was connected to a CD source

[@denischen8196]

How to solve if there is also a resistor in series with the capacitor? Can you use Thevenin equivalent to solve?

[@virtualrendezvous2220]

Very nice explanation sir👍👍👍

[@jahanzaib_kaleem]

Why is it in my syllabus then? 😭 We don't have notes for this either but there's a question for it in Alevel Physics

[@laiheakhong1345]

I am still not clear, why they always set up RC series circuit not RC parallel circuit? What is/are specific reason? Thanks

[@blackimp4987]

Thank you very much. It' been so hard finding this case. With your result I wrote it again but in term of vc as variable of the differential equation, this way bypassing the calculation of Q that in applications is usually less important. I wonder how would it be possible treating this case without R1. Don't tell me it doesn't exist an ideal tension generator without R1 as it could be electromotive force :)

[@user-sb5pr3nq4u]

thank you very much, I appreciated this analysis, and is really rare in books ! can you explain for us an analysis in the case where there is a diode instead of R1 ? thanks in advance

[@travellerpangaranto8977]

does the cap discharge through R2 when the cap reach full charge?, so the cap charging and discharging continuosly, source voltage V keep supplied to this

[@PhysicsNinja]

Once fully charged the current keeps flowing through R2. The current is due to voltage of power supply.

[@sipanget]

But what will happened if the voltage source is an alternating current (AC)?

[@beast7629]

Please take some question on heat dissipiated when switch changes

[@davisjohn1517]

Why is voltage across resistor 2 equal to 0? I thought at t=0 the capacitor acts like a wire so then all that is left is two resistors in series.

[@PhysicsNinja]

Hi Davis, there are different ways to explain this this but let's try this...if there is initially no charge on the capacitor the voltage across the capacitor equals to 0. If you use Kirchhoff loop rule around the outer loop you will find that i2 must be equal to 0 initially. Every branch on a parallel circuit will have the same voltage across it.

[@austindial2004]

How would I derive the transfer equation for this circuit when the output y(t) is the voltage across the capacitor?

[@sultan560]

yes

[@ashutoshkumar4004]

At 14:28, inisde bracket sign should be +ve. Isn't it?

[@navyaa7168]

At the=0+ u have removed R2 in loop equation?

[@yuhagsaeng]

Is this also applied on AC with square waveform?

[@battleclan]

Wait, how is exp(-(alpha*t)/(R1C)) an exponentially decaying funtion? A big value for t will result in a big exponent for e, which will be a big number? EDIT: I just saw the sign, it all makes sense now :)

[@PhysicsNinja]

Kexmonster yup negative sign will take care of it

[@xuhan1981v]

How to solve this problem in the limit of R1->0?

[@abdelhadibecheikh4257]

If we replace, R2 with CAP..is it the same??

[@PhysicsNinja]

No, you will have 2 caps in parallel. Replace them with an equivalent capacitor and redraw the circuit. It then become one resistor in series with an equivalent capacitor. Much easier problem.

[@johnnyjiggar3697]

Sorry u have taken integral dq/q-a = ln(q-a) where a = CV/alpha? Is this a mistake?

[@johnnyjiggar3697]

Instead u pulled the alpha / CV out for some reason did i miss something?

[@johnnyjiggar3697]

Oh i see it now its the lower limit

[@johnnyjiggar3697]

Ty

[@jamespeter4352]

Thanks alot for the video. Please, can you help explain how the first order differential equation will look like when the capacitor in the circuit is replaced by an inductor. Anticipating your response

[@PhysicsNinja]

James Peter have a look at my video list I’m pretty I have what you’re looking for.

[@antenismail4757]

capasitor charging speed based on R1. Is that true?

[@PhysicsNinja]

yes, and r2.. check out the time constant in my video

[@abhinavgusain0541]

Great explaination thanks

[@PhysicsNinja]

Abhinav Gusain thanks, it's much easier using thevenin equivalent circuit. Check out my new video.

[@mehmetpektas8249]

If we have variable dc voltage source(square wave) what will be happen

[@lailasmilgaine4867]

Great video! However, I wanted to ask would there still be a current flow through R2 if there was no R1, when capacitor is fully charged. I am asking this since it seems to me that potential difference between capacitor and battery would be zero and that,as I suppose, should be the same case for R2, since it is parallel to capacitor. Or maybe I am missing something. And would the result in the circuit you have displayed would be the same, if R2 and capacitor changed placed. Answer would be much appreciated!

[@PhysicsNinja]

Laila Smilgaine try taking the limit when R1 goes to zero and you'll get what you're looking for. Try also taking the short and long time limits when r1 is zero. In the long time limit there is no current i3 and all the current goes through r2.

[@lailasmilgaine4867]

Online Physics Ninja Okey, so if I understand it correctly, all the current goes through capacitor and R1 in the beginning in this circuit, and there is no current at the beginning through R2, bacause the voltage between junctions c and f is the same what between capacitor plates, and it is zero( so if there was no R1 in circuit, the current through R2 would be zero in the beginning as well because of voltage being zero, right?)After capacitor is fully charged, there is no reason for current to go to capacitor because it is fully charged therefore making the voltage difference zero, and all the current goes through R1 and R2. Am I correct? However, I am still wondering, if the charge on capacitor does not repel any charges also from the junction c, making continuous current flow through R1 and R2 impossible as well, or it does not happen that way and charge finds its way through R2, making the current flow possible? Also, would you get the same result and could you use the same method, as shown in video if capacitor plate and R2 switched places?Again, Thank you in advance!

[@user-fr9ec4xq1e]

Omg I literally love you so much

[@user-fr9ec4xq1e]

I didn’t know if the voltage was the same in all components of a parallel circuit or just in the resistors 😭🤚🏽

[@benreed6533]

What happens if resistor 1 is removed (i.e. R1 = 0)?

[@yusufkeskinoz9740]

physically in real life the capacitor explodes. theoretically you can solve the problem without it. nothing changes

[@bahadrguven6268]

is this inrush current ?

[@jumandas7960]

How to deal when capacitor is discharging.

[@mahmutgundogan8385]

thank you for explanation

[@simonmailhot4260]

Volume is far too LOW!

[@anonnymetoto8343]

can you do the transfer fonction of a 2 R with 2 C ? please

[@user-nj3di5uo5r]

Thank you for the video! What would be the purpose of this capacitor?

[@PhysicsNinja]

Glad you liked the video. There aren't a lot of applications for parallel capacitors for DC circuits but plenty for AC circuits. One benefit of this configuration is that you can still run current through another part of your circuit while charging the capacitor. If they are only in series the current would drop to 0 once the capacitor is fully charged.

[@user-nj3di5uo5r]

Thank you for the reply. Following a book for arduino projects, I saw they connect a capacitor parallel to a servo motor and was wondering what was its purpose.

[@katvi2597]

hi what if you exchange the position of the capacitor and resistor?

[@PhysicsNinja]

kat ville if you exchange the capacitor and resistor R1, you can start by simplifying the 2 resistors and writing them as an equivalent resistor. You'll be left with a simple RC circuit, except the R is the equivalent resistor.

[@MarkMcDaniel]

Guy, your volume detent for recording is set too low.

[@PhysicsNinja]

Snarky Mark new microphone now all audio issues have been fixed.

[@sau002]

Excellent

[@sudarshanseshadri5504]

Why did you go through sooo many textbooks, that seems like an awful lot of work haha

[@svendkorsgaard9599]

So in the Limit that R1=0, will the capacitor be instantaniously charged? According to the equations, the formula for chargé will reduce to Q=C*V. Is this correct? I had an exam question about this so any feedback will be really helpfull :)

[@PhysicsNinja]

Svend Korsgaard yes it will charge immediately.

[@mikesen2320]

I love your work, BUT CAN SOMEONE MAKE THIS STUFF USABLE. CAN YOU ACTUALLY PUT NUMBERS IN PLACE INSTEAD OF A BUNCH OF FORMULAS? CAN YOU SET UP A BREADBOARD AND PHYSICALLY SHOW HOW YOUR FORMULAE, HYPOTHETICAL NUMBERS AND ACTUAL CIRCUIT BEHAVOIR NUMBERS COME TOGETHER? WHAT IF WE WRITE ALL THIS FORMULAE AND FIND OUR RESULTS IN ACTUAL LAB TESTS ARE WRONG OR DONT COINXIDE WITH WHAT YOUR SAYING. AGAIN, great explaination, but how is it practical? What will be the actual circuit results and behaviors be if r1 is 100 or r2 is 500..etc....thanks.

[@mikesen2320]

People are so obsessed with the formulae and fail to display actual circuit behavior.

[@PhysicsNinja]

I understand your point but for a physicist putting in numbers makes the problem too specific. It’s practical I agree but you don’t learn anything. Seeing the equation and learning to understand what they mean, checking limits will build intuition and knowledge. At the end of the day any engineering student should be able to plug and chug.

[@mikesen2320]

Thank you sir. Please understand i meant no disrespect or ill will...your a good dude. One last question, would you have any videos regarding AC complex equations? Specifically for example series parallel circuitry...just curious...

[@PhysicsNinja]

@@mikesen2320 I have a playlist for AC circuits. It's a bunch of problems from the college class i taught. Good luck with your class.

[@farukben]

I don't get my answer but like for the effort (:

[@txjack03]

speak up bro

[@sanjumaurya8462]

Very very......Good

[@higgabes1]

at 18:08, shouldn't the equation be Q3(t) = alpha/CV instead of CV/alpha?

[@PhysicsNinja]

the units wouldn't work out if that were the case. alpha is dimensionless and Q= (Capacitance)*Voltage in order to get charge in Coulombs.

[@athantas]

can someone plz tell me wtf is happening when R1 is missing?

[@PhysicsNinja]

Capacitor charges instantaneously and a currenty flows through R2. No current where there's a capacitor because it's fully charge.

[@athantas]

@@PhysicsNinja thanks man.. i think makes sense now that you tell, so I will not ask why. But, can you please give me a hint how to work it when we have a current source instead of a V source?

[@athantas]

@@PhysicsNinja When again, R1 is missing :) thank you in advance

[@carpediembabee]

hocam bir tanesiniz

[@user-hq3gd6jp1c]

THANKS

[@wirelessone2986]

I need this on AC

[@arrabalimaz622]

you forgett to go through high school physics book dear

[@johnflower3669]

Thankssssss

[@vincenttran8415]

AP Physics 2 gang

[@navyaa7168]

I don't get dis