Basic Ciruits , dependent sources

  • Thread starter Ammar w
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  • #1
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Homework Statement



https://www.diigo.com/item/image/2sb3i/1svo [Broken]

Why don't we flip the signs of VA like this :

https://www.diigo.com/item/image/2sb3i/g2a4 [Broken]

because the current must flow from + to - of the resistor.

Homework Equations


none


The Attempt at a Solution


none
 
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Answers and Replies

  • #2
gneill
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The "+ -" tags on the 15Ω resistor tell you which way to "measure" the potential VA; It's like specifying how to orient the positive and negative leads of a voltmeter on the component.

You could change the tags as you suggest IF you also reverse the polarity of the controlled voltage source 2VA, since its output depends on how VA is "measured".
 
  • #3
28
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thanks
and the KvL equation changes from :
-120+V30+2VA-VA = 0

to :
-120+V30-2VA+VA = 0
 

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