Voltage is a height,
current is a flow
The loop lies flat; the staircase above it is the electric potential at each point of the circuit. The battery lifts charge up, each resistor drops it back down, and by the time you return to the start the total drop equals the rise exactly. That is Kirchhoff's loop rule, drawn as a shape.
whatA single loop drawn flat, with electric potential plotted as height above it. The battery is the step up; each resistor is a slope back down.
lawOhm's law at each element and Kirchhoff's loop rule overall: go once around and the rises must equal the drops, which is why the staircase closes.
trySwitch the second branch from series to parallel.
noticeParallel lowers the branch resistance, so current rises and the drop across r₁ grows — changing one element moves every other reading.
in lifeVoltage drops across a resistor chain are why a long extension lead dims the tool plugged into it.
found byOhm published the resistance law in 1827 to general scepticism; Kirchhoff formalised the loop rule in 1845.