# alternating current circuit calculations

Discussion in 'General Electronics Chat' started by omaroski, Oct 17, 2008.

1. ### omaroski Thread Starter Active Member

Jun 19, 2008
34
0
Hello,
sorry for the bad english but i'm from Italy.

If, in a capacitive circuit, i calculate capacitive reactance (knowing generator frequency and condensor's capacitance) through the formula:

Xc=1/2π*f*C

and then, knowing the RMS voltage of the generator i calculate the current with ohm's law:

I=V/Xc

can i get the RMS value for current and is the right way of doing the calculation or there's any problems related to voltage and current being out of phase?

Thank you, hope i explained it good
Omar

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
If the circuit does not include a resistor or other component in series or parallel with the capacitor then you can do it.

Mar 24, 2008
20,772
2,540
4. ### Ratch New Member

Mar 20, 2007
1,068
3
With the impedance formula, you mean.

If you use the RMS voltage, you will get the RMS current. If the resistance is negligible, then the current will lead the voltage by almost 90 degrees. A negligible amount of energy will be dissipated by the capacitor. I don't know, is there a problem with the phase of the current to the voltage being 90 degrees?

Ratch