Understanding Phase Change: R, L & C

[hidemi]

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?

 

[DaveE]

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?

 

[DaveE]

https://www.khanacademy.org/science...ac-analysis/v/ee-impedance-of-simple-networks

 

[hidemi]

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.

 

[DaveE]

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.

 

[hidemi]

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.