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Discussion in 'Homework Help' started by tosihiro2007, Nov 17, 2013.

  1. tosihiro2007

    Thread Starter New Member

    Feb 27, 2013
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    My professor asked me to also find the voltage drop V2(t) across the middle section using voltage divider (it's a section consists 30ohm in parallel to the 5mF capacitor).
    I found V(t) across current source, but I don't get the point of using voltage divider to get V2(t). Can't I just use the current going through the middle section and use ohm's law to find V2(t)?

    The equation for v2 is

    10angle45°(30+(-j/ωC)) but I didn't use voltage divider to find it.

    Could anyone explain me why I have to use voltage divider to get V2(t)?

    [​IMG]

    I apologize for putting "a" in the title. I couldn't post this thing because of the title so I put some random letter.
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    Whatever image you tried to embed isn't showing up. Please upload the image as an attachment to your post.
     
  3. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    And next time use a descriptive title. Don't ever post useless titles (i.e. one letter, or "need help!" or "urgent!"). Those types of titles are to be avoided at all times.
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    In his defense, he apparently tried posting with a more descriptive title and ran into our notorious title-length issue. So he went to the opposite extreme.

    I seem to recall that titles less than 20 characters seldom cause problems.
     
    Last edited: Nov 17, 2013
  5. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
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    If that's the case I apologize for being rude, but you can still post a descriptive title that doesn't turn up a blank page.
     
  6. tosihiro2007

    Thread Starter New Member

    Feb 27, 2013
    2
    0
    looks weird.... I just right clicked the image and opened in the new tab and it worked.
     
  7. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    You didn't post a link to the image, that's why....

    Here is the image:
    [​IMG]

    For future reference, upload the image to the forum as an attachment to your post:
    1. Click the paperclip icon (circled below in red)
    2. Click upload file and select the file you'd like to upload
    3. Once the file is finished uploading, copy the link to the image file you just uploaded
    4. Click the "Insert Image" button (circled below in green)
    5. Paste the URL you copied into the popup box
    6. Click "Okay" and your image will be attached as well as visible in your post...
    [​IMG]
     
  8. WBahn

    Moderator

    Mar 31, 2012
    17,718
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    Okay, now that we can see the circuit we can take a shot at answer your question.

    First, note that if you use the voltage divider approach you never need to determine the current in the circuit at all. But, having gone ahead and found the current, then yes, the easiest approach from that point to finding the voltage across the middle section is to use Ohm's law for impedances.

    But that's not the way you were told to do it. The bottom line is that the reason you have to use the voltage divider approach is because that is the approach you were instructed to use. Keep in mind that most circuit analysis problems can be solved using a variety of techniques. The only way to ensure that you learn each technique is to require you to use that specific technique.

    An effective way to get you to start developing the skills of determining when to use each method is to have you analyze the same circuit multiple times using a different method each time. So imagine what the answer would be to someone that asked why they need to analyze the circuit again when they've already found the answer some other way.
     
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