Current from an AC Capacitor

When a capacitor and a resistor are connected to AC lines, a constant current can be maintained through the resistor, so long as the Rectance of the capacitor is greater than the resistance of the resistor. The current flow depends on the value of the capacitor assuming that the input voltage is greater than the output voltage.

The current through the resistor R is

I RMS = V1 x X C

Where XC is the Rectance

As a rule of thumb, 70 – 75 milli amperes current will be available per uF from an AC capacitor


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  • bion

    Thanks ,,to you sir! You just made me understand what I couldn’t in class two days ago!,,,,,,, pls can you help me out ,,,,i mean ,,,pls can you lecture me privately?

  • Kuberkoos

    Ed, It is clear that you have major problems with something you have not taken the trouble to understand. Remember, 230V is ± 210 – 240 V depends on the load on the supply. 1uF capacitor can vary from ± 0.7uF to 1.1uF (depending on manufacturer). So, you must expect your results to vary somewhat. In the end you need measure the final result to get the exact value.
    Maybe the gentle art of dry flower arrangement would be more to your liking? 🙂

  • Sam

    Thanks, very informative

  • Ed

    XC C = X ?? whats wrong with calling C,,,C?

  • Ed

    I guess what I was saying is if X=I x this or that Then you don’t need I and X just X or I I being short for current, amps what ever in that way you don’t fill your head with worthless repetitive info.
    If I take a beginners class course of electronics and learn the fundementals of Ohms law or farraday or henrys ect ect and I learn the short hand symbols for these then you enter math equation,,ANOTHER seprate focal point and revise those symbols to represent X,,,Y or what ever WHY??

  • Ed

    even after all these years my brain still can’t grasp the complexity of mathmatical formulii!! Geezz why so complicated for un perfect science ?,, ie”rule of thumb 70 – 75 milliamper ect”
    Per uF vs Mpf nf on and on equate this to find that and yet still,,best guess 70 – 75. In my opinion,,which has not meant much to others and only for my own sanity,,THINGS are too dam complicated Find a focal point and stay with that point within its area divide , multiply subtract or add,,or a combo of those but pf Milli this or that too much to do to much paper to use if your brain can’t hold it. There has got to be a simpler time saving way to do these things then this only to get to a best quessed point of rule of thumb UUGHHH!!

  • gopala

    Dear Sir,
    It is higly educative. The beauty of the art of your presentation is that it is undestandable even to non technical people like me. THank you very much. Best wishes. V.GOPALAKRISHNA.

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