Calculating Capacitance in Parallel Circuits with AC Generator

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Homework Help Overview

The problem involves calculating the capacitance of two identical capacitors connected in parallel to an AC generator with a specified frequency and voltage. The context includes the use of RMS values for current and voltage.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the calculation of capacitive reactance and its relationship to voltage and current. There is an attempt to derive the capacitance from the given values, with some questioning the placement of decimal points in their final answers.

Discussion Status

Some participants have offered guidance on unit conversions and the interpretation of microfarads. There is acknowledgment of potential errors in decimal placement, but no consensus on the final answer has been reached.

Contextual Notes

Participants are navigating the requirements for submitting answers in specific units, which has led to confusion regarding the correct representation of capacitance values.

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Homework Statement


Two identical capacitors are connected in parallel to an ac generator that has a frequency of 660 Hz and produces a voltage of 27 V. The current in the circuit is 0.14 A. What is the capacitance of each capacitor? Note: The ac current and voltage are rms values and power is an average value unless indicated otherwise.


Homework Equations


Z = x of c = V/I
x of c = 1/(2pi*fc)


The Attempt at a Solution



x of c = 27V /.14A = 192.86 ohms

192.86 ohms = 1 / (2pi*fc) = 1 / (6.28*(660)c) = 1/(4144.8 x c)
c=1.25 uF

1.25uF equals the capacitance of the two identical capacitors connected in parallel.
The capacitance of each capacitor equals 1.2uF/2 = .625 uF

This answer is incorrect, but I have absolutely no idea what I'm doing wrong.. Thanks for any help!
 
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Looks okay to me!
 
They're asking me to submit my answer in units of F, and I think I may just have my decimal point in the wrong place... (I submitted .625 F). And now I'm confusing myself a lot as to where the decimal place really should be. Should my final answer actually be 6.25x10^-13 F?

6.25x10^-7 uF x (1x10^-6 F / 1 uF) = 6.25x10^-13 F ?
 
micro means 10^-6
.625 uF = .625 x 10^-6 F = 6.25 x 10^-7 F
 
Whew, dumb mistake on my part. Thanks!
 

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