Voltage drop across paralell resistor and capacitor

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Discussion Overview

The discussion revolves around finding the voltage drop across a resistor and capacitor in parallel, specifically using complex numbers and impedance. Participants are exploring the application of complex impedance in this context, including calculations and interpretations of results.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant expresses uncertainty about the correct application of complex impedance and whether to treat it like resistance, questioning whether to take the modulus or real part.
  • Another participant suggests calculating the complex impedance using the standard formula for resistors in parallel and applying Ohm's law to find the complex voltage across the net impedance.
  • A participant seeks clarification on the method to find the magnitude of the complex quantity, specifically asking if it involves taking the square root of the product of the complex quantity and its conjugate.
  • A later reply confirms that the method for finding the magnitude is indeed to take the square root of the product of the complex quantity and its complex conjugate.

Areas of Agreement / Disagreement

Participants are generally exploring the same problem but express varying levels of confidence and understanding regarding the application of complex impedance. There is no clear consensus on the best approach to take.

Contextual Notes

Participants have not fully resolved the implications of using complex impedance in this scenario, and there may be missing assumptions regarding the definitions and calculations involved.

teroenza
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Homework Statement


Find the voltage drop across a resistor and capacitor in parallel. I am trying to understand how to deal with this using complex numbers. I may have a completely wrong notion of complex impedance. I thought I could treat the complex impedance like resistance, then take the modulus or real part (I believe I know the math, but not which to apply).


I= 100 milli Amps
R= 1000 ohms
C= 0.001Farads
freq.= 60Hz=377rad/s



Homework Equations


Z_c=1/(i*omega*C)

R_eq= (R*Z_C)/(R+Z_C)


The Attempt at a Solution


Do I apply the standard resistors in parallel formula then take the real part of the modulus? Or do I have a completely wrong conception on complex impedance.
 
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teroenza said:

Homework Statement


Find the voltage drop across a resistor and capacitor in parallel. I am trying to understand how to deal with this using complex numbers. I may have a completely wrong notion of complex impedance. I thought I could treat the complex impedance like resistance, then take the modulus or real part (I believe I know the math, but not which to apply).


I= 100 milli Amps
R= 1000 ohms
C= 0.001Farads
freq.= 60Hz=377rad/s



Homework Equations


Z_c=1/(i*omega*C)

R_eq= (R*Z_C)/(R+Z_C)


The Attempt at a Solution


Do I apply the standard resistors in parallel formula then take the real part of the modulus? Or do I have a completely wrong conception on complex impedance.

Calculate the complex impedance as you've suggested using the 'usual' formula for resistors in parallel. Apply Ohm's law to find the (complex) voltage that will appear across the net impedance when driven by the 100mA current. The magnitude of that complex quantity should be what you're looking for.
 
To be sure I fully understand, by magnitude you mean take the square root of (my complex quantity * its complex conjugate) ?
 
teroenza said:
To be sure I fully understand, by magnitude you mean take the square root of (my complex quantity * its complex conjugate) ?

Yes.
 

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