Understanding Phase Shift in RC Circuits

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Homework Help Overview

The discussion revolves around understanding phase shift in RC circuits, specifically focusing on the relationship between resistance, capacitive reactance, and phase angle. Participants are exploring how to calculate the phase angle in the context of an RC circuit.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply a formula for phase angle that seems more suited for RLC circuits, expressing confusion about its relevance to RC circuits. Some participants suggest using the cosine relationship involving resistance and capacitive reactance. There is also a question regarding the definition of capacitive reactance.

Discussion Status

Participants are actively engaging with the problem, with some providing mathematical relationships that could be relevant. There is acknowledgment of a negative phase angle, indicating a possible resolution to part of the inquiry, though the overall understanding of the phase shift remains under discussion.

Contextual Notes

There is a mention of confusion regarding the definitions and calculations related to capacitive reactance, and the original poster notes a specific concern about the applicability of certain formulas to the RC circuit context.

pat666
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Homework Statement


Pls see the attachment.


Homework Equations





The Attempt at a Solution


Obviously I have B and C correct but for a the only thing I can find is tan(phi)=XL-Xc/R
This seems to be for a series RLC circuit though and I only have RC.
also I know that the current lags the p.d by 900 in an RC circuit but I can't see how I can use this?
any help appreciated.
 

Attachments

  • PF.jpg
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Phase angle can found by using

cosφ = R/sqrt(R^2 + XC^2)
 
Last edited:
I don't know capacitive inductance though?
 
pat666 said:
I don't know capacitive inductance though?

Sorry. It should be XC. = 1/ωC
 
Thanks that worked, although the answer was negative 89 degrees?
 
You can use the equation tan(phi)=(XL-Xc)/R for a series RCL circuit, even for XL=0 as it is the case now.

ehild
 

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