Why Does Voltage Between A-B Change When Source Voltage Changes in a Circuit?

Hi guys, whenever I have circuit which I want to calculate the between A and B over voltage source 5v, I calculated the voltage between A-B and it's 3v for instance, then lets assume I have change the voltage source to 3v, then the voltage between A-B is 1.5v ... all is fine for me, but where did the previous voltage between A-B which is 3v gone? I mean it's now 1.5V but where did 3v gone? can anyone explain to me how 3v gone ? it was 3v, when I changed the source voltage, the voltage is now 1.5v between A-B .. where did the previous voltage between A-B gone?!

@ryan " I have change the voltage source to 3v, then the voltage between A-B is 1.5v"" where did the previous voltage between A-B which is 3v gone? I mean it's now 1.5V but where did 3v gone?You should know- You're the one who changed it from 5 volts to 3 volts!Ryan- may  I suggest that you find some local people where you can sit down and talk about electricity and electronics.  Do a Google search to see if there are any "Maker" groups in your area.  If you don't find any, try searching for Amateur ("Ham") Radio groups.  You'll most likely find a lot of helpful people there. -Rick

Hi rick,you seem that you think Im troll or something ..I'm really serious and face this problem two days ago.
 but previous amount of the "changed" where did they gone? I mean 3v?I know I changed it, but changed isn't meaning that 3v gone, where did they go after changing the source voltage?

Ryan,In any circuit, when you change the voltage source, the voltages in the rest of the circuit will change. It sounds as if you are thinking of a voltage as being a permanent thing when it's not.
Any time you have a resistor connected between two points with different voltages, the resistor allows current to flow which can cause the voltage to change.

Ryan when you post questions like this it is very difficult for us not to think you are a troll.Where did you find this problem?  There is no reference to an internet site.  There is no picture or diagram.  We have no way of knowing what you are looking at or thinking about.  One of your previous questions (About voltages (0/1) below) you said you had posted a picture, you did not, I reminded you of this, and you still have not posted a picture.  Who but a troll would do this?
We all have jobs here and can not spend so much time on foolish questions from you, when you do not seem to listen to what we say.  I said in a previous post that you need to learn Ohms law and the other laws of electricity and you don't seem to have done so, else you would not be asking questions like this.If you want to learn electronics, get yourself on a proper course, we do not seem to be able to teach you anything here.