A battery drives one lamp, and the supply ammeter reads 0.6 A. A second, identical lamp is wired in parallel. The reading climbs to 1.2 A.
The new branch has the full 6 V across it, so it draws its own 0.6 A. The first branch is untouched: still 6 V across it, still 0.6 A through it. The battery now supplies both branches at once.
Same source voltage, twice the current. A circuit that lets more current flow at the same voltage is opposing the current less — its resistance is lower.
Neither lamp changed. Each lamp keeps its own resistance; it is the combination that resists less. That is why the more-resistors trap fails: a new resistor does not add opposition when it opens a new path.
A third identical heater joins two heaters already in parallel. What happens to the supply current?
Why does adding a parallel branch lower the combined resistance?
One branch of a parallel pair is disconnected. What happens to the combined resistance of what remains?
Adding a component raises the total resistance in one circuit type and lowers it in the other. Which pairing is right?