Potential difference between two points (VA - VB)

In summary, the conversation discusses solving for the voltage difference between points VA and VB in a circuit with a closed switch. The solution involves using the junction rule and loop rule to find the currents in the circuit, and then using those currents to calculate the voltage difference. One person in the conversation is unsure if their calculation is correct and is seeking confirmation.
  • #1
johnknee
15
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Homework Statement


Q. With the switch closed, what is the voltage difference, VA-VB ?

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Homework Equations


Junction rule: I3 = I1 + I2
Loop rule(s)

The Attempt at a Solution


I solved for the currents in this circuit when the switch is closed.

Top loop(clockwise): +10V1 - 15*I1 - 47*I1 + (0V since I'm assuming no Voltage drop across switch) = 0
Bottom loop(counter clockwise): -5*I2 + 6V2 - 22*I2 + 0V = 0

For the top loop: I isolated I1 and got 10/62 = 0.161 = I1
For the bottom loop: I got 6/27 = 0.222A = I2
I1 + I2 = 0.161 + 0.222 = 0.383A.= I3

for the voltage difference VA - VB, I tried doing this with the guidance of a friend.
Va = 10 - I1*15 = 7.585 V.
Vb = Va - Vc - 6 (Vc being the voltage at node C where I3 flows through.)
Then Vc = Va - i1*47 = 7.585 - (7.567) = 0.018 V.
Vb = Va - Vc - 6 = 7.585 - 0.018 - 6 = 1.567 V.
Finally Va - Vb = 7.585 - 1.567 = 6.018 V

I am not sure whether I did this part correct.
 
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  • #2
You already have a thread dealing with this circuit. You must keep all related questions in that thread.

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