EEVblog 1618 - The Equation For Energy In A Capacitor

[@filips7158]

"Clear as mud?" - I laugned so hard at this. If we are being rigorous, every single line was mathematically questionable, yet the result is correct. Man I love EE

[@EE_Overload]

Oh, how i miss videos like these!

[@brooklyndrive]

Thanks Dave, I work as an ER doctor but was a telco tech in my younger days. I often think of this when turning a defibrillator on!

[@Artopiumcom]

Short and SWEET! Clear as mud on a rainy day!

[@AlanTwoRings]

Video is titled "The Equation For Charge In A Capacitor" but you gave us the equation for Energy in a capacitor. The equation for charge is just Q=CV.

[@EEVblog]

Damn, title brain fart

[@BillAnt]

@@EEVblog - Does the same equation and linearity apply in super-caps too?

[@retiredjan4714]

@@BillAnt *YES* a super-cap is also a cap(acitor).

[@BillAnt]

​@@retiredjan4714 - Right but super caps can pack more energy in the same volume of space.

[@retiredjan4714]

@@BillAnt Not sure about that i think it is in the same range Q = C x V A supercap has a very low voltage 2.7 Volt and 400 Farat, while electrolytic caps start at 16 V 10 uF and go up too 600 V 5 mF (m for milli, u for mirco)

[@IanScottJohnston]

OMG....this takes me back to school! They made a big point of deriving where all the equations came from.

[@afourtrackmind]

Eff the algorithm! I love these short videos!

[@charlesvanneste2834]

These are great! I would love to hear EEVblogs take on a capacitor discharging into another capacitor and where the lost energy goes (aka his take on the two capacitor paradox)

[@keithking1985]

Wow, that was quick and to point and bloody awesome 👍🇮🇪🙏

[@mahmoudgaber5347]

if the term C.dV/dt, representing the current charging the capacitor -as in the case here- then the dV/dt is dependent on the charging current (the current source) not the opposite. Yes mathematically I(t) = C. dV/dt, but physically you're making a cross referencing. Also according to this equation, there must be a voltage variation with time so that the capacitor can source/ sink current (dV/dt must have a value other than zero)

[@amirmoezz]

Very short and educative, Love it.

[@HiltsR]

GREAT video, some educational videos are just needed for enlightening and for people to learn, please sometimes ignore the viewer counts.

[@dataplatter]

That is a proper thumbnail

[@entropyachieved750]

Would have loved watching these during my apprenticeship at the start of the 2000s. Also I'd use a delta (triangle) for change

[@benschwald4029]

Thanks for the educational videos

[@radekhladik7895]

Its funny to see him try to avoid the integration so hard.... But as soon as you see 1/2*c*x^2, be sure that it is the integration of linear function - kinetic energy, freefall, acceleration,....

[@javieralejandrocalasierra6600]

Thank you.

[@ats89117]

You're kind of proving the given there. Real men start with Maxwell's Equations!

[@gamingdojo6126]

you wrote "charge in a capacitor' on the whiteboard but it's actually the equation for energy in a capacitor :)

[@gigaherz_]

I have a software engineering degree, and we did some introductory electronics on the first year. It wasn't a whole lot, but we did touch on resistors, inductors, capacitors, zener diodes, and I think we just lightly touched BJT transistors. The part that I found more of a chore was capacitor charge/discharge calculations. Not relevant to the video really, just reminded me of it.

[@briansauk6837]

Painful to not see a trivial integral to do it properly

[@RalphWu55]

Love your work

[@gblargg]

I'm trying to intuitively grasp how voltage is squared. This implies that if you charge it for double the time, you get 4x the energy. Would this be because to maintain a constant current, the energy is constantly increasing? (since the constant current source has to increase voltage to maintain that current)

[@ChrisSmith-tc4df]

I believe that there is a similar follow on geometric explanation as to why the effective capacitance of two equal series capacitors halves as well.

[@GalgoczkiAdam]

"the separation distance, adds up" en.wikipedia.org/wiki/Capacitor#/media/File:Kondensator_C1_C2_Reihe.svg

[@keithking1985]

​@@GalgoczkiAdamvery cool link. 👍🇮🇪

[@KeritechElectronics]

Back to the basics!

[@michaelpiotrowicz6100]

Thanks Dave, this is great

[@nithingovindaraj7394]

Need more videos like this

[@ME1D]

where is the fulll video? and thanks for your effort

[@jasonzurlo1543]

Great stuff

[@jdatdeface]

When I need this 15 years ago, I simply used equation U*C=I*T Question: how big capacitor I need when switching load from PSU1 to PSU2 to prevent power glitch (and restart) on load. Spreadsheet to help and done in few minutes.

[@n.mishev]

Nice video

[@bertblankenstein3738]

Here is a question: A capacitor with a known value and charge (and therefore energy) is connected to a discharged capacitor of equal value. I assume that the charge moves such that it is now equal between the two capacitors, the voltage for each capacitor drops to half. So each capacitor has 1/4 of the initial total energy. Where did the other half of the energy go?

[@user-dj1hy6zc6q]

There's some bad math involved there. When did 1/2 * 2 = 1/4?

[@bertblankenstein3738]

@@user-dj1hy6zc6q when half the charge moves to the other capacitor, the voltage for each capacitor drops to half the initial value. If the energy is CV^2/2, you get 1/4 of the initial energy.

[@ChrisSmith-tc4df]

Why do you presume that the voltage will halve at paralleled equilibrium?

[@alexv3780]

If you have 1F capacitor charged with 2J energy then if you measure the voltage will be 2V. If you have 2F capacitor charged with 2J then the if you measure the voltage will be √2V. The relation between capacitance and voltage is not linear.

[@keithking1985]

​@@alexv3780interesting 🤔 The auld gray matter is sparkling after reading that. 👍🇮🇪🤔

[@petersage5157]

It's not the energy stored in the capacitor that shocks you, it's the rapid discharge of that energy over a short time.

[@jonaskuliesius6802]

C=q/V and V=E/q, so E=q^2/C . Hmmm(?)... Or Take E=Vq, plug in q=CV and get E=VC^2 ... I can see that he gets 1/2 from integrating dV/dt, but does that mean I'm wrong? Am I stupid?

[@gooseknack]

Yep, perfectly clear..😉

[@MadawaskaObservatory]

very good

[@gleradon]

Now I finally understand what my high school teacher was trying to teach me.

[@Ricard2k]

😂

[@charliesullivan4304]

I was expecting a teardown to assess the build quality of the whiteboard markers

[@PraxZimmerman]

Bro I needed this video so bad a week ago

[@EEVblog]

I'll hop in my Delorean

[@ctrlj]

@@EEVblog The Equation For Charge In A Flux Capacitor

[@jacobeller]

​@EEVblog Oh, man! I think I get it! You're making a funny about time travel because that is the car that was used in Back to The Future! Right? Am I correct? Please tell me! Because my friends and family, they say that I'm retarded and sometimes it makes me cry, but also sometimes I am right and please answer my question and show them that I'm wrong or at least not retarded this ONE time, PLEASE! THANK YOU SO MUCH I'LL SIGN UP FOR YOUR patreon and everything, I promise if you tell me if I got the joke, because that was a joke, right?! Right? Oh, man......maybe I am retarded. ......oh, man. I'm stupid. That WAS the joke......but everyone knows that, but because I pointed ot out and wanted it confirmed, that actually means I'm stupid........doesn't it? I'm so stupid 😮😮😮😮😢😢😢😢😢😢😢😢😢😢😢😢😢😢😢😢😢! I'm sorry. Didn't mean to waste your time. Please don't try to tell my family......they'll make fun of me and point at me and laugh.......😢😢😢😢😢😢😢😢😢😢😢😢😢

[@nameredacted1242]

@@jacobeller Nah, you are off by 39 years.

[@namenotshown9277]

Store lightning energy? Possible with capacitor bank........can you do some numbers on it?

[@ArnoldSommerfeld]

The energy is stored in the fields, not in "the capacitor". Tell me you don't know how to calculate the energy in the fields without telling me you don't know how to calculate the energy in the fields.

[@sarahmanalapan8443]

Honestly it might help if you show the factoring out.

[@feicodeboer]

Fortunately I still understand this ...

[@3beltwesty]

Where are the missing volt nut ppms?

[@TimoNoko]

Fanciest capacitor ever was two metallic plates of very precise shape. When charged enuff there is eventually spark at one corner. The spark advanced along the edge at speed of light gathering energy and tight laser beam is emitted. Never managed to do that even after studying the patent carefully.

[@jakubromanski2439]

I havent even seen this video!!! KZbin didnt show it to me

[@orencomputerelectronics8751]

how to convert from J to Wh. Q(c)=It=UC => E=Q*U because when you pull current from capsitor the voltage drops from VCC up to 0V. then E=Q*U/2=>E(joul)=C*U^2/2. in hour had 3600 sec i put this and get P(Wh)=C*U^2/7200=>>>> it mean if i will use this power at one hour it take P power.

[@grhinson]

I wonder if this will help with the KZbin algorithm?

[@and9290]

This hurts my brain.

[@3beltwesty]

I really cannot draw any current from my unsaturated standard cells. So sad :)

[@frosty129]

Could have posted that as an April fools educational video

[@jonnscott4858]

The Equation Pur Energy In A Catacitor, since he's skinning a cat or Tui.

[@naeemhaq3504]

nice

[@platin2148]

I must say the algo didn‘t even show it to me.

[@aldob5681]

worst performer video? must see it....

[@zlac]

Why would you skin a cat though?

[@GermanMythbuster]

*FAKE! This is not the Real Dave!* Dave is physically incapable of making Videos under 10 min. This must be AI Generated. 😂

[@sennheisermxsennheisermx]

why u look so old

[@xephael3485]

I hate algebra

[@atheistaetherist2747]

Dave haznt a clue re how a capacitor charges, & Dave (& everyone else) is even worse re a capacitor discharging. The actual graph(s) are nothing like what Dave (& everyone else) reckons. Ivor Catt explains. Electricity is actually elekticity.