Looking for capacitive reactance but missing "C"

  • Thread starter Thread starter tessie0407
  • Start date Start date
  • Tags Tags
    Reactance
Click For Summary

Homework Help Overview

The discussion revolves around finding the capacitive reactance (Xc) in a capacitor circuit with a frequency of 1000 Hz, where the value of capacitance (C) is not provided. Participants are exploring how to derive Xc without having all the necessary parameters typically given in class examples.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Some participants discuss the formula for capacitive reactance and express confusion about the missing capacitance value. Others suggest using the graphs provided to derive reactance or rearranging related equations to find Xc.

Discussion Status

The discussion is active with various approaches being considered. Some participants have offered alternative methods to calculate Xc based on available data, while others are questioning the correctness of the formulas and the notation used in calculations.

Contextual Notes

Participants note that previous examples included both capacitance and frequency, which is not the case here. There is also mention of potential notation errors in expressing current values.

tessie0407
Messages
7
Reaction score
0
1. Current and voltage graphs are shown for a capacitor circuit with ƒ=1000Hz.
What is the capacitive reactance Xc?




2. I know the equation is Xc= 1/2∏ƒC to solve for capacitive reactance but where do I find C? All of our in class examples had C and ƒ given.



The Attempt at a Solution

 

Attachments

  • 20140722_171959-1[1].jpg
    20140722_171959-1[1].jpg
    18.4 KB · Views: 443
Physics news on Phys.org
tessie0407 said:
2. I know the equation is Xc= 1/2∏ƒC to solve for capacitive reactance
That formula is not correct. You need a pair of brackets to set it right or you'll never get the right answer!

What would be the equation for current if you connect that capacitance C to an AC voltage source V volts?
 
tessie0407 said:
1. Current and voltage graphs are shown for a capacitor circuit with ƒ=1000Hz.
What is the capacitive reactance Xc?

2. I know the equation is Xc= 1/2∏ƒC to solve for capacitive reactance but where do I find C? All of our in class examples had C and ƒ given.

The Attempt at a Solution

Get the reactance from the graph.


What are peak voltage & peak current?
 
The only other thing I can think to do is rearrange ΔVc= I*Xc

Xc= ΔVc/I
Xc= 10V/10x10^-2 A which gives me 100Ω
 
tessie0407 said:
The only other thing I can think to do is rearrange ΔVc= I*Xc

Xc= ΔVc/I
Xc= 10V/10x10^-2 A which gives me 100Ω
10V looks right for the voltage. But that's not the right way to write 10mA.
 

Similar threads

Change in Capacitor for largest possible Current
  • · Replies 2 ·
Replies
2
Views
2K
The potential difference across an inductor
  • · Replies 9 ·
Replies
9
Views
10K
The relationship of the current before and after a change.
  • · Replies 16 ·
Replies
16
Views
2K
But is it the same for AC circuits?
  • · Replies 9 ·
Replies
9
Views
2K
RLC Circuit Behavior with Changing Frequency, Capacitance, and Voltage
  • · Replies 2 ·
Replies
2
Views
2K
Calculate Resonant Frequency & Capacitive Reactance
  • · Replies 3 ·
Replies
3
Views
4K
AC voltage across a parallel branch
  • · Replies 5 ·
Replies
5
Views
2K
Frequency in an AC circuit given capacitance, voltage, and current
  • · Replies 6 ·
Replies
6
Views
4K
How can capacitive reactance be zero for no capacitor?
  • · Replies 4 ·
Replies
4
Views
3K
The phase difference between current and voltage.
  • · Replies 30 ·
2
Replies
30
Views
5K