AS Daily A Level Physics question
A 6 V supply powers a single filament bulb rated for 6 V. A second identical bulb is then connected in parallel across the same supply using short leads. Assume the supply maintains constant voltage and the leads’ resistance is negligible. What happens to the brightness of the original bulb, and why?
Answer
The correct answer is C.
Correct: C — It stays about the same because the voltage across it is unchanged. A is wrong because although the total current drawn from the battery increases, the current in each parallel branch is set by the unchanged supply voltage, so the original bulb doesn’t get more current. B is wrong because in parallel the current does not get “shared” through a single component; each branch draws its own current from the same voltage. C is correct because the original branch still has the full supply voltage, so its power (and brightness) is unchanged. D is wrong because adding an identical bulb in parallel does not create a near-zero resistance path; the total resistance halves but is not a short, so the original bulb stays lit.