EEVblog 1618 - The Equation For Energy In A Capacitor

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How To Derive The Equation For Energy In A Capacitor, E = 1/2 C.V²
NOTE: Re-edited from an old impromptu video to remove all unrelated stuff about the dumpster whiteboard I found.
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Опубликовано:

20 май 2024

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Комментарии : 81

@filips7158 Месяц назад

"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 Месяц назад

Oh, how i miss videos like these!

@AlanTwoRings Месяц назад

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 Месяц назад

Damn, title brain fart

@BillAnt Месяц назад

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

@brooklyndrive Месяц назад

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 Месяц назад

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

@afourtrackmind Месяц назад

Eff the algorithm! I love these short videos!

@amirmoezz Месяц назад

Very short and educative, Love it.

@IanScottJohnston Месяц назад

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

@WilhelmEley Месяц назад

Which means you went to a good school! Though I expected he'd do it from first principles (maxwell's equations), which would also be possible in the video length

@keithking1985 Месяц назад

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

@charlesvanneste2834 Месяц назад

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)

@RalphWu55 Месяц назад

Love your work

@michaelpiotrowicz6100 Месяц назад

Thanks Dave, this is great

@benschwald4029 Месяц назад

Thanks for the educational videos

@ats89117 Месяц назад

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

@KeritechElectronics Месяц назад

Back to the basics!

@nithingovindaraj7394 Месяц назад

Need more videos like this

@radekhladik7895 Месяц назад

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,....

@jasonzurlo1543 Месяц назад

Great stuff

@HiltsR Месяц назад

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

@dataplatter 26 дней назад

That is a proper thumbnail

@n.mishev Месяц назад

Nice video

@entropyachieved750 Месяц назад

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

@mahmoudgaber5347 Месяц назад

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)

@PraxZimmerman Месяц назад

Bro I needed this video so bad a week ago

@EEVblog Месяц назад

I'll hop in my Delorean

@ctrlj Месяц назад

@@EEVblog The Equation For Charge In A Flux Capacitor

@jacobeller Месяц назад

@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 Месяц назад

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

@MadawaskaObservatory 26 дней назад

very good

@gamingdojo6126 Месяц назад

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

@gooseknack 23 дня назад

Yep, perfectly clear..😉

@charliesullivan4304 Месяц назад

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

@gigaherz_ Месяц назад

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.

@ChrisSmith-tc4df Месяц назад

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 Месяц назад

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

@keithking1985 Месяц назад

@@GalgoczkiAdamvery cool link. 👍🇮🇪

@gleradon Месяц назад

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

@Ricard2k Месяц назад

😂

@ME1D Месяц назад

where is the fulll video? and thanks for your effort

@petersage5157 Месяц назад

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

@jdatdeface Месяц назад

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.

@gblargg Месяц назад

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)

@sarahmanalapan8443 Месяц назад

Honestly it might help if you show the factoring out.

@namenotshown9277 11 дней назад

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

@feicodeboer Месяц назад

Fortunately I still understand this ...

@jakubromanski2439 Месяц назад

I havent even seen this video!!! RU-vid didnt show it to me

@naeemhaq3504 Месяц назад

nice

@bertblankenstein3738 Месяц назад

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 Месяц назад

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

@bertblankenstein3738 Месяц назад

@@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 Месяц назад

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

@alexv3780 Месяц назад

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 Месяц назад

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

@briansauk6837 Месяц назад

Painful to not see a trivial integral to do it properly

@jonaskuliesius6802 Месяц назад

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?

@TimoNoko Месяц назад

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.

@and9290 Месяц назад

This hurts my brain.

@3beltwesty Месяц назад

Where are the missing volt nut ppms?

@platin2148 Месяц назад

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

@orencomputerelectronics8751 Месяц назад

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.

@3beltwesty Месяц назад

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

@grhinson Месяц назад

I wonder if this will help with the RU-vid algorithm?

@jonnscott4858 Месяц назад

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

@frosty129 Месяц назад

Could have posted that as an April fools educational video

@WilhelmEley Месяц назад

I just wanted to tell you, we love you also if you don't do the mr. beast thumbnail faces.

@ArnoldSommerfeld Месяц назад

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.

@zlac Месяц назад

Why would you skin a cat though?

@aldob5681 Месяц назад

worst performer video? must see it....

@xephael3485 Месяц назад

I hate algebra

@atheistaetherist2747 Месяц назад

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.