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Trying to understand how voltage \$ V_{D1} \$ is found.

Here's the original circuit with solution:

enter image description here

Here's how I think it can be redrawn, basically the grounds are just one node:

enter image description here

So to find voltage \$ V_{d1} \$ one first considers what's voltage at point 1, positive side of \$V_{d1}\$ right?

Well, at point 1, voltage is what? \$ -10K \times 1.33mA? \$

How about voltage across 5k resistor? Point 1 is between 10k and 5k resistors...

For point 2 it's 0, since the node of that point is connected to ground, right?

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  • \$\begingroup\$ Here's a similar, simpler question, i.imgur.com/yV5EAyX.jpg. Basically, what's the voltage at point 1? Is it: (current through R1) times R1 + (current through R2) times R2??? \$\endgroup\$
    – Jack
    Oct 17, 2017 at 1:52

1 Answer 1

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For \$V_{D1}\$ you can consider two KVL loops—they should both give you the same answer.

At point 1, you could start from the leftmost source (start from the ground) and say:

$$ \text{10V}-i_{D2}(10\text{k})-V_{D1}=0$$

schematic

simulate this circuit – Schematic created using CircuitLab

You already have the current then solving for \$V_{D1}\$ results in \$V_{D1}=-3.3\text{V}\$

You may also use another KVL loop:

schematic

simulate this circuit

$$ V_{D1}-i_{D2}(5\text{k})-(-10\text{V})=0$$

And solving for \$V_{D1}\$ will result in the same.

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