Understanding Phase Shift in RC Circuits

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In the discussion on phase shift in RC circuits, the user seeks clarification on calculating the phase angle, initially confusing the formula for series RLC circuits with their RC circuit. They correctly identify that the current lags the voltage by 90 degrees in an RC circuit and inquire about the use of this information. The phase angle can be determined using the formula cos(φ) = R/sqrt(R^2 + XC^2), where XC is the capacitive reactance. After correcting their understanding of capacitive reactance, they find that the phase angle is negative 89 degrees. The conversation emphasizes the distinction between series RLC and RC circuits while providing insights into calculating phase angles in RC circuits.
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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.
 

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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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