Have you ever encountered a question asking you to find what is V1 and V2?
This kind of question is of course relatively tricky but the core concept is a beauty to understand.
Right off the bat, you will want to know the understanding behind
what the battery is all about
The battery’s job is to drive electrical charges around the circuit
Can you see that the electrons are very happy to travel from one end of the battery to another?
The secret of being a battery is the idea that electrons are attracted from one terminal to another.
Attraction = force
The attractive force on our electron heading to the other terminal causes it to move a distance!
Force x distance moved in direction of force = energy
So the point I am driving at, is that
battery supplies electrons moving around the wire with energy!
Even if you don’t get the front part, you need to know that the battery’s main job is to hand out energy to electrons departing one terminal to the next!
Next the role of the resistor
The resistor is there to suck energy out of electrons running around the wire
In diagrams with 1 resistor,
that one resistor suck out all the energy of the electrons passing though!
In diagrams with 2 resistors,
our electrons cannot possibly lose all their energy after encountering one resistor and got no energy left for the next resistor!
So nature has it in such a while that you add up the resistance of both resistors to get the TOTAL RESISTANCE
the total resistance is what the electron will need to deal with!
Let say our charge needs to run around 2 resistors one with 4ohms and one with 8ohms and our electron is supplied by a 12V battery,
He will use up 12V of energy in total against the total resistance of 12ohms
Against the 4ohm resistor on the other hand, he uses up 4V of energy!
And against the 8ohm one, he uses up the remaining 8Vs!!!