Understanding Phase Change: R, L & C

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Homework Help Overview

The discussion revolves around the concept of phase change in electrical circuits, specifically focusing on resistors (R), inductors (L), and capacitors (C) and their impact on voltage and current relationships.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the reasons for considering phase changes, particularly in relation to complex impedances and their effects on voltage and current. Questions are raised about the phase relationship between current and voltage in inductors.

Discussion Status

There is an ongoing exploration of the implications of phase shifts caused by complex impedances. Some participants provide insights into the nature of current lagging behind voltage in inductors, while others express gratitude for clarifications offered.

Contextual Notes

Participants are discussing the implications of phase shifts in the context of homework problems related to electrical engineering, specifically focusing on the behavior of different circuit components.

hidemi
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Homework Statement
If the input to an RLC series circuit is V = Vm Cos ωt, then the current in the circuit is?
The answer is (D) as attached.
Relevant Equations
V = IZ
Z = [ R^2 + (XL - Xc)^2]^1/2
Why do we need to consider phase change?
Here are my thoughts: is it because voltages are different in phase for each of the three electrical accessories, R, L and C?
 

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Because complex impedances will, in general, cause a phase shift between the voltage applied and the current. It's what they do. Suppose Z is just an inductor, would the current be in phase with the voltage?
 
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DaveE said:
Because complex impedances will, in general, cause a phase shift between the voltage applied and the current. It's what they do. Suppose Z is just an inductor, would the current be in phase with the voltage?
No, the current will be lagged after voltage.
 
hidemi said:
No, the current will be lagged after voltage.
Which will appear as a phase shift between the voltage and current. That is why phase matters for complex impedance problems.
 
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DaveE said:
Which will appear as a phase shift between the voltage and current. That is why phase matters for complex impedance problems.
Thank you for your further explanation.
 

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