your math is spot on as far as it goes in the top section and you state that the total voltage across the resisters is 3 v 12V - 9V = 3V that is correct.
but than in the lower statement 9 + 0.94 + 0.54 = 10.48 where did you get the extra 9 V you only have 3V left to work with.
the polarity of the 2 sources is subtractive 12 - 9 = 3 you can't just plug in an extra 9 volts. it has to come from someplace. and you haven't accounted for it. is there a magic power source that is not shown. all voltages and current must be accouted for.
the 9V source on the left was used to reduce the 12V to the 3 again 12 -9 = 3
now you have taken away the 9 V source it can't just pop up again it needs to be there
I wish my back account worked that way
take money out and it just refills I don't have to put anything in it just happens you cant get something for nothing
if you can't understand that then I can't explain it. go back to electricity 101 the first thing you should have leraned
the 9V source on the left was used to reduce the 12V to the 3 again 12 -9 = 3
now you have taken away the 9 V source it can't just pop up again it needs to be there
I wish my back account worked that way
take money out and it just refills I don't have to put anything in it just happens you cant get something for nothing
if you can't understand that then I can't explain it. go back to electricity 101 the first thing you should have leraned
The question was "Calculate the voltage at point B in the given circuit."
That is impossible to answer, because the question does not specify what reference for the voltage should be taken.
To be pedantic, it would have been better if the question had been worded "Calculate the potential at point B in the given circuit.". At least that would infer a voltage above ground potential....
I personally hate questions that are given in exams or tests that do not meet one very simple criteria.....
"Is the question ambiguous" - of course in this case it is. You have to make an assumption that the questioner means "with respect to ground potential", but he didn't say so.
Anyway, enough ramblings about the question, the answer is 10.48V "above ground potential"
It is easy to calculate...
Total Potential Difference (wrt ground) across the four resistors = 3V
Total Resistance = 47K + 27K + 56K + 20K = 150K
Current through all resistors = V/R = 3/150000 = 0.00002 A
Volt drop across the 47K resistor = 0.94V
Volt drop across the 27K resistor = 0.54V
Volt drop across the 56K resistor = 1.12V
Volt drop across the 20K resistor = 0.40V
Either way you look at it the potential, above ground, at point B is...
9 + 0.94 + 0.54 = 10.48
or,
12 - 0.40 - 1.12 = 10.48
Thanks to everybody... very educational!
@daba, This post helped me immensely! It really broke it down.
Two questions: Does your breakdown assume the current is flowing one way or the other? Or is that determined by laws of polarity in the circuit just how it's sown?