# need help with an RLC exercice

Discussion in 'Homework Help' started by Mugiwara303, Jun 14, 2015.

1. ### Mugiwara303 Thread Starter New Member

Jun 14, 2015
8
0

can someone solve this for me please! thank you!

Aug 21, 2008
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3. ### Mugiwara303 Thread Starter New Member

Jun 14, 2015
8
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is everything right?

4. ### WBahn Moderator

Mar 31, 2012
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No, because you are failing to take into account the phase angles of the two currents.

5. ### Mugiwara303 Thread Starter New Member

Jun 14, 2015
8
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tell me, the question 2 are right?

6. ### WBahn Moderator

Mar 31, 2012
17,777
4,804
No, it is not right, because you are not taking into account the phase angles of the two currents.

That equation applies only if the two currents are at 90 degree difference to each other. But even without the resistor the two currents would be 180 degrees apart. With the resistor, they are at some relatively arbitrary angle relative to each other.

Break each current into its real and reactive components.

Jun 14, 2015
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8. ### shteii01 AAC Fanatic!

Feb 19, 2010
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use complex notation

9. ### Mugiwara303 Thread Starter New Member

Jun 14, 2015
8
0
i dont know how to use it! can anyone make the solution for me

10. ### WBahn Moderator

Mar 31, 2012
17,777
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This is Homework Help, not Homework Done For You. Just giving you the solution will not help you. You have almost certainly seen examples worked in your course material. You have almost certain seen examples worked by your instructor. If you haven't learned the material from those, how will having yet one more problem worked for you make any difference? What will you do on the exam? Ask the proctor to make the solution for you?

You need to struggle and fight with these concepts in order to learn them. So go back and look at how you represent impedances, voltages, and currents using phasors and how to add two phasors together. Then make your best attempt at just that part of the problem.

11. ### shteii01 AAC Fanatic!

Feb 19, 2010
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How do you represent inductor using complex notation?

12. ### crutschow Expert

Mar 14, 2008
13,050
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Look at this to start.

panic mode likes this.
13. ### WBahn Moderator

Mar 31, 2012
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My guess (and the TS would need to confirm this) is that they aren't using complex notation for anything at all, but rather phasor notation and a slew of formulas aimed to minimize the need for a background in algebra and trig.

14. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,397
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I bet you are right.

15. ### WBahn Moderator

Mar 31, 2012
17,777
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@Mugiwara303 : You know (or should know) from KCL that

$
\bar{I_T} \; = \; \bar{I_L} \; + \; \bar{I_C}
$

But these are phasors and have to be added as such. So the first thing is to draw the phasors for I_L and I_C, keeping in mind that I_L includes both a reactive (inductive) and resistive part. So the real first thing is to find I_L by using KVL.

16. ### Mugiwara303 Thread Starter New Member

Jun 14, 2015
8
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its really complicated for me to explain to you LoL! i need to know this as fast as i can i don't have time... can anyone give me the detailed solution and i will understand then! thanks in advance.

17. ### JoeJester AAC Fanatic!

Apr 26, 2005
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And when you write a proposal or are the boss and have to explain something, will you use that same excuse?

18. ### WBahn Moderator

Mar 31, 2012
17,777
4,804
I refer you to Post #10. If the examples you've seen worked haven't made you understand it, how will yet one more magically do the trick. You want understanding without effort on your part and it just seldom works that way.

19. ### Mugiwara303 Thread Starter New Member

Jun 14, 2015
8
0
just give me the solution please! i told you guys that i don't know how to solve it and i really need this!

20. ### Mugiwara303 Thread Starter New Member

Jun 14, 2015
8
0

is this right?