Two identical bulbs are connected to the same battery, once in series and once in parallel. In the series circuit, the current is measured as 0.5 A everywhere in the loop. In the parallel circuit, each branch is measured separately. Which statement correctly compares current and voltage in the two circuits?
- In both the series and parallel circuits, the current is shared out equally between the two bulbs while the voltage across each bulb stays the same as the battery's voltage
- In the series circuit, the same 0.5 A flows through both bulbs one after another, while in the parallel circuit the total current from the battery splits between the two branches, with the full battery voltage appearing across each branch
- In the series circuit, the voltage is the same across both bulbs while the current splits between them, and in the parallel circuit the current is the same everywhere while the voltage splits between the branches
- The parallel circuit only works if the current is reduced to exactly half of the series circuit's current, because splitting the wire path always halves the current automatically
Why B? And why not the others?
Correct answer: B. In the series circuit, the same 0.5 A flows through both bulbs one after another, while in the parallel circuit the total current from the battery splits between the two branches, with the full battery voltage appearing across each branch
In a series circuit, there is only one path for charge to flow, so the same current passes through every component one after another; in a parallel circuit, the current from the battery splits between the separate branches, but the full battery voltage appears across each branch because each one connects independently back to the battery. The option claiming current is shared and voltage stays the same as the battery's voltage in both circuit types is wrong because that describes only the parallel case, not the series one, where the current instead stays constant throughout the single loop. The option describing the series circuit as having equal voltage and split current, and the parallel circuit as having equal current and split voltage, is wrong because it has the two circuit types' behaviour completely swapped. The option claiming a parallel circuit always exactly halves the current is wrong because how the current divides between branches depends on the resistance of each branch, not a fixed automatic halving rule.
Source: BBC Bitesize GCSE Physics: Series and parallel circuits