When trying to find the voltage between two points on a schematic I get the opposite answer


I have the following schematic:


simulate this circuit – Schematic created using CircuitLab

I need to calculate \$V_{AC}\$. I figure \$V_A = 12V\$ relative to ground and \$V_C = 0V\$ relative to ground meaning my answer should be:
V_{AC} = V_C – V_A = 0V-12V = -12V
But, the textbook I am following says it should be \$+12V\$. Why am I wrong?

Best Answer

\$V_{AC}\$ corresponds to

$$ V_{AC} = V_A - V_C = 12 V $$

You interpreted bad relationship subscripts.

Look at the references in your textbook. Surely, the author has defined how to interpret the notation.

Also, points B and C, are the same pontencial so that

$$ V_A = V_{AB} = V_{AC} = 12\,\mathrm{V} $$