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I'm studying Kirchoff's Laws and how to find $\Delta V$ between two points in a circuit (CC). I already know how to use it but I look on internet for more exercise to learn more and find this circuit

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I'm a little confuse about it, because there is a wire in between that don't understand exactly. In this case I wanna find $\Delta V_{AB}=V_A-V_B$. I start to do this:

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I write $$\Delta V_{AB}=V_A-V_B = \Delta V_{AC} +\Delta V_{CD} +\Delta V_{DB} $$

Then if I apply Kirchhoff's voltage law in right part $$ -30 + 6 I_3 + 4 I_3 =0$$ and I have the relations $$ I_1 =2 A \quad \quad \Delta V_{AC}=5 I_1 \quad \quad \Delta V_{CD} =5-10 I_2 \quad \quad \Delta V_{DB}= 4 I_3 $$ But I'm not sure how to find $I_2$

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  • $\begingroup$ So based on the answer given what is $V_{AB}$? $\endgroup$
    – Bob D
    Feb 14, 2021 at 12:01

1 Answer 1

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First, notice that the supplied current of the current source, must be equal to the current that flows through the 'back' of it, and therefore must be equal to the current that flows 'upward' from node $C$:

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Then, applying KCL on node $C$:

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Yields: $$I_1 = I_1 +I_2$$

$$I_2=0A$$

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  • $\begingroup$ How it is possible? I though that there should be non-zero current in all the wires... $\endgroup$
    – user239504
    Feb 14, 2021 at 21:10
  • $\begingroup$ Why would it not be possible? The current that the current source supplies is $I_1$, and the upper most current in this part o the diagram has to be $I_1$, and that tells us that $I_2$ must be $0$, according to Kirchhoff's Current Law. $\endgroup$
    – uriyabsc
    Feb 14, 2021 at 21:46
  • $\begingroup$ How do you know that in A->C segment have to be I_1? Should not be $I_1=I_2+I_4$? (Where $I_4$ is another current that we don't know from C to A). Sorry, maybe I miss something in between $\endgroup$
    – user239504
    Feb 14, 2021 at 22:18
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    $\begingroup$ I've edited my answer in order to clear that confusion up, I hope this helps :) $\endgroup$
    – uriyabsc
    Feb 15, 2021 at 9:18
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    $\begingroup$ great! Thank you very much :) $\endgroup$
    – user239504
    Feb 15, 2021 at 12:48

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