# Electronic – How does voltage know

resistorsvoltage

How is it possible that in scenario 1 resistor `R1` converts 5V of energy to heat and in scenario 2 the same resistor `R1` converts 2.5V of energy to heat?

The resistor `R1` in both scenarios are exacly the same, I don't seem to grasp what happens on the physical level to the electrons how they "know" when to dump all their energy at once in resistor `R1` in scenario 1 or to divide the energy they have proportionally over the resistors `R1` and `R2` in scenario 2.

I have read an explenation here, but it's still not clear. How is it possible that the voltage is different at point `A` going through the same amount of resistance? I would expect a linear relation between voltage and resistance.

Could someone explain what physically happens that causes this? simulate this circuit – Schematic created using CircuitLab

Edit

Is my understanding right? According to here

The resistance drops liniar along the path.

In scenario 1 at the start of `R1` the resistance the current encounters is 100\\$\Omega\\$ and at the end of `R1` it encounters 0\\$\Omega\\$.

In scenario 2 at the start of `R1` the resistance the current encounters is 200\\$\Omega\\$ and at the end of `R1` it encounters 100\\$\Omega\\$.

If this is true, why does point `A` in scenario 2 have more volt left if it has encountered a higher resistance of 200\\$\Omega\\$ at the beginning opposed to scenario 1 where it encountered 100\\$\Omega\\$ at the beginning?

How is it possible that the voltage is different at point A going through the same amount of resistance?

In scenario 1 it is 0 volts (as you have labelled it). In scenario 2 is is half the voltage applied i.e. 2.5 volts.

I would expect a linear relation between voltage and resistance.

Not when potential dividers are used unless both resistors change value proportionally.

Ohms law, I = V/R so, in scenario 1 the current is 5/100 = 50 mA. In scenario 2, I = 5/(100 + 100) = 25 mA.

Ohms law again: V = IR so the voltage across R2 is 25 mA x 100 ohms = 2.5 volts.