AS Daily A Level Physics question
A student powers one small torch bulb from a 6 V battery. They then add a second identical bulb in parallel with the first using short, negligible-resistance wires. Assume the bulbs behave like simple resistors over this range. Which statement must be true when the second bulb is connected?
Answer
The correct answer is D.
Correct: D — Each bulb has the same brightness as before, and the current from the battery increases. In parallel, each bulb is across the full battery voltage, so each draws the same current and power as a single bulb; adding a branch lowers the total resistance so the battery supplies more total current. A … Wrong because although current splits between branches, each branch still has the full battery voltage, so the current in each identical bulb does not reduce. B … Wrong because reducing total circuit resistance does not raise the fixed battery voltage across each bulb; each bulb’s brightness stays the same. C … Wrong because adding a parallel path reduces total resistance, so the total current drawn from the battery increases, not decreases. D … Right because per-bulb conditions are unchanged (same voltage, same brightness) while the total current rises due to the extra parallel branch.