Hello /sci/. I'm a fucking brainlet.

The question is find the voltage Vac.

Why is the answer for this circuit -3V?

It makes no fucking sense, how am I supposed to solve this type of question???

>>16732473 (OP)
so basically voltage is the difference in electric potential, just like when you raise a bucket of rocks up you are creating a difference in gravitational potential.

the difference in potential between A and B, is -2V, and from B and C is -5V

to find the TOTAL difference, the difference in electric potential of AC, is the same as BC - AB.
(think that we are trying to remove the "B" as the middleman algebraically)

-5v - (-2v) = -3V

>>16732473 (OP)
when applying kirchoff's laws, think of potential difference as elevation differences.

>>16732473 (OP)
It literally linearizes the voltage

>>16732473 (OP)
For fucks's sake man.
Kirchoffs laws is just the axiomatization of the idea of a circuit.
A cycle has to have 0 potential because you're literally measuring to the same spot.
A node has zero net current because you're counting the current in and out from every path.
These assumptions are obviously unphysical, but that's the point of the approximation.
You can hardly call these things laws, more like basic deductions about circuits/paths.

>>16732473 (OP)
Holy filtered. Pay attention in class.

HOW DOES THIS EVEN WORK?

I thought this was one of those non-sense problems but I literally can measure the difference between two batteries like this just by hooking up positive to positive

I just don't get it, theres nothing for my meter to consider ground? batteries must act different when they're arranged like this because if I isolate the system, and say measure the positive of one batter and the negative of another, no voltage even though my meter is definitely seeing +9v on one end and -9v on the other

>>16732542
child, learn how to derive kirchoff's laws from maxwell's equations

>>16732473 (OP)
Per continuity - current flux through conductors in a conserved quantity, the current going into a branch is equal to the current going out of the branch. i.e. - The Junction Rule

Per Faraday's Law - change in potential about a closed loop is proportional to the change in magnetic flux, so for a non-inductive load, the potential difference across any closed circuit is zero. i.e. - The Loop Rule

>>16732778
Kirchoff's work predates maxwell's, Mr. grown-up.
Regardless what's the point of deriving it?
The laws apply just as well to abstract circuits other than EM (fluids etc.).

https://www.youtube.com/watch?v=njrt5IHE9Oo

Voltages add but if you have opposite polaricity you negate it first