0
$\begingroup$

enter image description here

For the diagram above, the following voltages are specified:

$V_A = 4V$
$V_D = 2V$
$V_a = 0V$

Here, $V_{ab}$ indicates the voltage referenced from node b to node a. In other words, imagine $V_{ab}$ being identified in the diagram as having a "-" at node b and a "+" at node a. The other voltages are specified using the labeled references. $V_a$ is the value of the voltage potential at node a.

Question 1: Find the value of $V_B$ in volts and enter it in the box below.

Question 2: Find $V_{ab}$

Question 3 For the same circuit above, find $V_C$ and enter it into the space below without units. ($V_C$ is the voltage across the top element, not the voltage at the point c in the circuit.)

I'm teaching myself linear circuits and came across these problems. I got Question 1 correct but cannot understand questions 2,3.

Question 1: Since $V_B$ is in parallel with $V_A$, I thought $V_B = 4V$. Is this the correct thinking?

Question 2: Since $V_a = 0V$, the voltage at this node is 0V. We also determined the voltage across $V_B$, so I thought this solution would also be 4V-- but this is incorrect. Can someone please explain why?

Question 3: Not sure.

$\endgroup$

closed as off-topic by BMS, ACuriousMind, Kyle Kanos, David Z Jan 6 '15 at 21:25

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – BMS, ACuriousMind, Kyle Kanos, David Z
If this question can be reworded to fit the rules in the help center, please edit the question.

0
$\begingroup$

Question 1: Since VB is in parallel with VA, I thought VB=4V. Is this the correct thinking?

Yes.

Question 2: Since Va=0V, the voltage at this node is 0V. We also determined the voltage across VB, so I thought this solution would also be 4V

Remember your sign convention. $V_{ab}$ is defined with an opposite sign convention from $V_A$ or $V_B$.

Question 3: Not sure.

You need to use Kirchoff's Voltage Law (KVL) here.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.