Question

Hello, I wold like to ask a question about circuit.

Answer 1

I let Vb = 0 V (ground voltage)
Then, by KCL at node A,
(Va+10)/10 + (Va-30)/10 + Va/20 = 0
So, Va = 8 V,
The answer Vb - Va = -8 V
Am I correct?

Answer 2

@Zale101 @sweetburger

Answer 3

@.Sam.

Answer 4

Yes ...

Answer 5

You are absolutely correct!

Answer 6

Thanks for your help! @samigupta8 @Sachintha

Answer 7

Np.

Answer 8

I wasn't of any help for you. :3 Why did you took the voltage at b as 0? It's certainly not grounded.

Answer 9

We can take 0 at any position as per our convenience ..and we have to ensure that the rest of the voltages are set accordingly..

Answer 10

You can use Millman's Theorem to easily check this answer - https://en.wikipedia.org/wiki/Millman%27s_theorem

Answer 11

Since you assumed point B as ground then Point A voltage (with respect to B or ground) seems to be +8 volts. I may be wrong, but maybe recheck everything and see..
I took your equation and multiplied all terms by 10 getting:
Va + 10 + Va - 30 + Va/2 = 0
2.5 Va = 20
Va = 8 (positive)

Answer 12

@radar but that's exactly what he said, didn't he? Va = 8 and Vb - Va = -8. No?

Answer 13

Maybe that is what is being said. Since Vb is 0 as he is referring that as ground. Va must be positive 8 volts. And by gosh, 0 - (+8) = -8 volts. I am used to solving for a voltage with reference to the reference (the point where he stated he was using as ground. If I measured Va it would be +8. In retrospect, you are correct, that is what he is saying, I didn't say he was wrong, just saying I was having some difficulty relating his answer to Va.