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So by using KCL to solve for a node voltage Vds (branch consisting of only a resistor Rds -> Ids = Vds/Rds,) if I obtain a negative answer for Vds, does this mean that the sign I used for the current flowing through Rds is actually reversed and that my answer is correct?

In other words, if you're solving for the voltage and you obtain a negative result, how do you interpret it and what would the correct answer be?enter image description here

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  • \$\begingroup\$ Please be polite and add a schematic. The button is on the editor toolbar. \$\endgroup\$ – Transistor Jan 31 '16 at 23:29
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The way I wrote my KCL equations had the current of the branch shown flowing into node Vds. By passive sign convention the current has to flow from + to - on the resistor, so the negative sign pointed to the fact that I reversed this.

I think the key is to be mindful of what each term in a KCL equation represents (current) and if a - sign shows up, track it back to the corresponding current. In my case, the question asked for the voltage with this polarity, meaning that I needed to reverse my sign.

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KCL is a very simple method. Just let if currents are entering into a node then it is +ve and otherwise it is negative. Write down your equations like this. You will find that you have automatically get your desired answer.

In your case you have chose a polarity of voltage. It is not a very big deal that you are choosing the right polarity or not.

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