Find Current in RC Circuit w/ V=Vo Sin(ωt)

Click For Summary
SUMMARY

The discussion focuses on calculating the current in an RC circuit with a voltage source defined as V = Vosin(ωt). Key equations include the impedance Z = R + jX, where XL = jωL and XC = -j/(ωC). The user attempts to derive the current phasor for the capacitor, \hat{I}_{C}, using the relationship \hat{I}_{C} = (\hat{V} - \hat{V}_{R})/X_{C}. The user expresses uncertainty about the phase angle ø and its implications on the current in the resistor, indicating a need for clarification on the phase relationships in AC circuits.

PREREQUISITES
  • Understanding of AC circuit analysis
  • Familiarity with phasors and complex impedance
  • Knowledge of the relationships between voltage, current, and impedance in RLC circuits
  • Basic proficiency in complex numbers and Euler's formula
NEXT STEPS
  • Study the concept of impedance in RLC circuits, focusing on the calculations for Z = R + jX
  • Learn about phasor representation of AC voltages and currents, including phase angles
  • Explore the derivation of current in capacitors and inductors in AC circuits
  • Investigate the implications of phase relationships in AC circuit analysis, specifically for resistors and reactive components
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in AC circuit analysis and design will benefit from this discussion.

TheEvenfall
Messages
3
Reaction score
0
Hello there, I'm not sure if my solution is correct for \hat{I}_{C}

Homework Statement



In the given circuit, calculate the current in each circuit element given that V = V_{o}sin(ωt)
R, L and C are given.
http://imgur.com/yO3flg8

Homework Equations


Z = R + jX (j^{2} = -1)
X_{L} = jωL
X_{C} = \frac{-j}{ωC}
\hat{V} = V_{o}e^{jωt}
\hat{I} = I_{o}e^{j(ωt-ø)}
I_{o} = \frac{V_{}}{|Z|}
tan(ø) = \frac{\Im(Z)}{\Re(Z)}

The Attempt at a Solution


First for the impedance, 1/Z_{XL} = 1/X_{L} + 1/X_{C}
Z_{XL} = j\frac{ωL}{1- ω^{2}CL}
Z = R + Z_{XL} = R + j\frac{ωL}{1- ω^{2}CL}
The current phasor in the resistor R: \hat{I_{R}}= \hat{I}= \hat{I_{C}} + \hat{I_{L}}
\hat{V_{C}} = \hat{V} - \hat{V_{R}}
\hat{I_{C}} = (\hat{V} - \hat{V_{R}} )/X_{C}
\hat{I_{C}} = (V_{o}e^{jωt} - I_{o}e^{j(ωt-ø)})(jωc) = V_{o}ωCe^{jwt}(1-\frac{R}{|Z|}e^{-jø})(j)
\hat{I_{C}} = V_{o}ωCe^{j(ωt+\pi/2)}(1-\frac{R}{|Z|}e^{-jø}) ø and |Z| are known.
AndI_{L} can be found the same way.
I'm not entirely sure my solution is correct. Also, since I_{R} is always in phase with V, does that mean that ø is 0? If so, then tan(ø) is also 0 but that would mean that either ω or L are 0...

Note: sorry if it seems slobby and for the skipped steps, my exam is in less than 3 hours and I'm really nervous and running out of time.
 
Last edited:
Physics news on Phys.org
Good luck with your exam! Don't worry too much about this last exercise. The assumption Ir is in phase with V seems incorrect to me.
 
well I'm still working through it, but one thing I want to point out is your source voltage is wrong. e^iwc =cos(wc) +isin(wc)
if you want to use eulers id. you want (e^iwc - e^-iwc)/2 , but that seems unnecessary, i'd just keep it v_s or something until you have your final answer, then sub in V(not)sin(wt). also it looks like complex analysis only? no time dependent ? just wondering.
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
1K
Replies
4
Views
1K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 21 ·
Replies
21
Views
2K
  • · Replies 3 ·
Replies
3
Views
1K
Replies
12
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K