A student connects a battery to two bulbs in a series circuit. The student then reconnects the same two bulbs in a parallel circuit using the same battery. Explain how the potential difference across each bulb and the current through each bulb differ between the two circuits.

In a series circuit the two bulbs are connected end‑to‑end, so the battery voltage is divided between them. Each bulb therefore experiences only a fraction of the supply potential difference. The same current flows through each bulb because there is only one path for the electrons.

In a parallel circuit the bulbs are connected to the same two points of the battery. Each bulb is therefore exposed to the full battery voltage; the potential difference across each bulb equals the supply voltage. The current from the battery splits between the two branches, so each bulb receives a portion of the total current. Consequently the total current drawn from the battery is larger in the parallel arrangement than in the series arrangement, because the equivalent resistance of the parallel circuit is lower.

Thus: series – voltage divided, same current through each bulb; parallel – full voltage across each bulb, current split, larger total current from the battery.