Measuring voltage on same side of resistor

[akimhaneul]

1) why is it that when measuring voltage, it has to be in reference to something else? I learned that if you measure voltage on the same side of resistor, you get 0 because it's same voltage

2) why is it that in a series circuit with resistors, the current is same? Shouldn't each resistor cause less desire for charges to move? Is it because charges can't pile up and they don't go anywhere so they have to move to the other side anyway?

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[Asteri]

1) Types of potential energy that deal with fields (i.e. gravitational fields, electromagnetic fields) are measured in relation to other objects, as there are no "absolute" values. For example, in gravitational fields when you are doing problems, most of the time the reference is the ground, as that is a lot more relevant than discussing the potential energy with relation to the core of the Earth. In this case, there is no "absolute" potential energy, as the energy depends on what you are comparing the object to (i.e. the ground, Earth's core, the Sun). Similarly, with electromagnetic fields (this includes circuits) only the difference in energy matters, and there isn't an absolute measure. A voltage of 0 means that from the beginning of the measure to the end, there is no change in potential energy. If you do not have a resistor, then there will be no change in voltage as nothing will have used up the electrical potential energy.

2) Current is the flow of charge, and as charge is conserved from beginning to end a circuit (resistors cannot store charge) the current is the same from beginning to end of a linear system. Each resistor takes up some of the energy of the flowing electrons, but the electrons do not stop - they keep on flowing towards the (+) end of the battery. The voltage decrease here is a change in the potential energy of the electrons, not in the number.