Total XC for capacitors in parallel

[adamr8223]

Is it just me or is the answer to this is 44.78 ohms? Or am i crazy???


Three capacitors, a 12 µF, a 20 µF, and a 30 µF, are connected in parallel to a 60 Hz source. The total XC is

[GavinK5]

Your answer seems to be correct but I got 42.78 ohms when I did the calculation...

Formula for capacitors in parallel is simply CT = C1 + C2 + C3 and then plug that into XC = 1 / (2 × π × f × C).

First, find total capacitance...
CT = 12 µF + 20 µF + 30 µF
CT = 62 µF

Then find capacitive reactance...
XC = 1 / (2 × π × f × C)
XC = 1 / (2 × 3.141... × 60 × 0.000062) = 42.78 ohms

Don't forget to use the decimal form for microfarads when calculating capacitive reactance (0.000062 not 62).

Edit: changed farads from 0.0062 to 0.000062

[lester mcmanaway]

Your answer seems to be correct but I got 42.78 ohms when I did the calculation...

Formula for capacitors in parallel is simply CT = C1 + C2 + C3 and then plug that into XC = 1 / (2 × π × f × C).

First, find total capacitance...
CT = 12 µF + 20 µF + 30 µF
CT = 62 µF

Then find capacitive reactance...
XC = 1 / (2 × π × f × C)
XC = 1 / (2 × 3.141... × 60 × 0.0062) = 42.78 ohms

Don't forget to use the decimal form for microfarads when calculating capacitive reactance (0.0062 not 62).

microfarad is to the millionth place. 1uF would be .000001. I believe it would be .000062

[GavinK5]

microfarad is to the millionth place. 1uF would be .000001. I believe it would be .000062

ah, you are right, not enough zeros in my original equation. post updated. thanks, lester!

[adamr8223]

Your answer seems to be correct but I got 42.78 ohms when I did the calculation...

Formula for capacitors in parallel is simply CT = C1 + C2 + C3 and then plug that into XC = 1 / (2 × π × f × C).

First, find total capacitance...
CT = 12 µF + 20 µF + 30 µF
CT = 62 µF

Then find capacitive reactance...
XC = 1 / (2 × π × f × C)
XC = 1 / (2 × 3.141... × 60 × 0.000062) = 42.78 ohms

Don't forget to use the decimal form for microfarads when calculating capacitive reactance (0.000062 not 62).

Edit: changed farads from 0.0062 to 0.000062

I fat fingered that. 42.48 is what i got as well

[AmberCorey]

Hi, I have a question
What is the maximum voltage that can be applied between the terminals of the series combination of 0.1microF,250V and 0.2microF 500V capacitors

[3Ashockers]

Solving for total capacitance and finding reactance is the easiest and best way to prevent math errors. Simple math gives the answer as 42.78 ohms.

To double check: Find the reactance of each individual capacitor, then find the Rt for the three in parallel. I did it on a non scientific calculator with some quick rounding and came up with an answer of 42.9 ohm, which is close enough for me!