3 ms·

The author clearly states immediately after that image: Note in the above, I’m not saying that is -6V and +6V, which would be 12 volts total, I’m just labeli

The author clearly states immediately after that image: Note in the above, I’m not saying that is -6V and +6V, which would be 12 volts total, I’m just labeling the positive and negative sides of the 6 volts of power available. Context matters! See image: https://i.imgur.com/3fIZFFe.png https://i.imgur.com/3fIZFFe.png

kazinator 5y ago
The diagram is bad; the context is worse. Firstly, "volts of power" even by itself is very, very poor language in an EE topic, never mind "positive and negative sides of 6V of power". By labeling two nodes of a circuit as -6V and +6V, you are showing that that's what the voltages are at those points (relative to some common reference) and thus the potential difference between them is 12V. That's the standard interpretation when you put a number next to a node of the circuit, and put a V suffix on it. What the diagram is communicating, to someone who can read circuits, is that R2 is dropping 12V, on a DC supply of 9V. The diagram is also neglecting to show some ground reference that is understandable as 0V, to indicate relative to what are those other voltages being referenced. By convention, the default place for that would be the - terminal of the battery. So the bottom of R2 would be shown as 0V, and the middle of the voltage divider, top of R2, as 6V (which matches what is already notated). It may be that the -6V is supposed to be referenced from the top of the R2 resistor, but this is confusing and inconsistent; all voltages for the same circuit should use the same reference. If you want to show that the bottom of R2 is down 6V from the top, you can label those nodes of the circuit, like R2a and R2b, and then write a formula: R2b - R2a = -6V which shows that R2b is -6V down from R2a.
lmilcin 5y ago
The context just suggests the author has no idea what they are doing. That's not how any electronics engineer would label schematic and it is clearly wrong way to do it. Typically there is voltage reference selected and marked somewhere on the schematic. By tradition, if you don't mark it, it defaults to negative battery terminal. The rest of voltages would be understood in comparison to the reference point. More complex circuits might need multiple reference points. For example, a PSU converting from 230V AC to 12V DC will need at least two reference points.

kazinator 5y ago

The diagram is bad; the context is worse. Firstly, "volts of power" even by itself is very, very poor language in an EE topic, never mind "positive and negative sides of 6V of power". By labeling two nodes of a circuit as -6V and +6V, you are showing that that's what the voltages are at those points (relative to some common reference) and thus the potential difference between them is 12V. That's the standard interpretation when you put a number next to a node of the circuit, and put a V suffix on it. What the diagram is communicating, to someone who can read circuits, is that R2 is dropping 12V, on a DC supply of 9V. The diagram is also neglecting to show some ground reference that is understandable as 0V, to indicate relative to what are those other voltages being referenced. By convention, the default place for that would be the - terminal of the battery. So the bottom of R2 would be shown as 0V, and the middle of the voltage divider, top of R2, as 6V (which matches what is already notated). It may be that the -6V is supposed to be referenced from the top of the R2 resistor, but this is confusing and inconsistent; all voltages for the same circuit should use the same reference. If you want to show that the bottom of R2 is down 6V from the top, you can label those nodes of the circuit, like R2a and R2b, and then write a formula: R2b - R2a = -6V which shows that R2b is -6V down from R2a.

lmilcin 5y ago

The context just suggests the author has no idea what they are doing. That's not how any electronics engineer would label schematic and it is clearly wrong way to do it. Typically there is voltage reference selected and marked somewhere on the schematic. By tradition, if you don't mark it, it defaults to negative battery terminal. The rest of voltages would be understood in comparison to the reference point. More complex circuits might need multiple reference points. For example, a PSU converting from 230V AC to 12V DC will need at least two reference points.