Circuits - AC circuits / phasor

  • Thread starter wcjy
  • Start date
  • #1
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Homework Statement:
Given the following circuit with the voltage source V=5 cos(t+θ) and the resistor R1=1.1(Ω) and the inductor L1=0.8(H). The impedance Z_eq of the circuit and the phasor current I can be respectively described as

$$Z_{eq} =a+jb $$
$$I= I_o ∠ Φ $$

Find a, b, and Io in these expressions.
Relevant Equations:
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1617012401915.png
1617012427653.png
1617012478928.png


Hi, my school has no answer key provided. and would like to check if this is correct. Thanks!
 

Answers and Replies

  • #2
gneill
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Hi. It looks like you've correctly found the equivalent impedance and the magnitude of the current (both without units though). However, you'll need to account for the phase angle θ of the source in your Io.
 
  • #3
73
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Hi. It looks like you've correctly found the equivalent impedance and the magnitude of the current (both without units though). However, you'll need to account for the phase angle θ of the source in your Io.
From the question, I_o is without phase angle. where I = I_o ∠ Φ. That is why i didn't account for the phase angle.

side note: how do you input latex for like I_o in the text
 
  • #4
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It's ##I_{0}## [sharp(#) sharp(#) I_{0} sharp(#) sharp(#) ]
 
  • #5
gneill
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From the question, I_o is without phase angle. where I = I_o ∠ Φ. That is why i didn't account for the phase angle.
Presumably you'll need to specify what ##\Phi## is, no?
 
  • #6
73
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Presumably you'll need to specify what ##\Phi## is, no?
i dont need to but is it even possible, since they did not give angle ##\theta##
 
  • #7
417
95
You need ##\theta## to compute ##\varphi##
 
  • #8
gneill
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i dont need to but is it even possible, since they did not give angle ##\theta##
You can specify ##\Phi## in terms of ##\theta## and the impedance's angle.
 
  • #9
DaveE
Science Advisor
Gold Member
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You can specify ##\Phi## in terms of ##\theta## and the impedance's angle.
Yes, phase shift matters in AC circuits.
 

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