A student has a battery connected to a buzzer and a lamp. The student first connects the buzzer and lamp in series, then reconnects them in parallel. Explain how the brightness of the lamp and the total current from the battery differ between the two arrangements.

WJEC GCSE Physics (Wales) — 1.1 Electric circuits · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

In the series circuit the same current flows through both the buzzer and the lamp, so the battery voltage is divided between them. Consequently the lamp receives only part of the battery voltage and its brightness is reduced.

In the parallel circuit each component is connected directly across the battery, so both the buzzer and the lamp receive the full battery voltage. The lamp therefore shines brighter than in series.

Because the parallel arrangement provides two separate paths, the total current drawn from the battery is greater than in the series arrangement.

In the series arrangement the total resistance is the sum of the buzzer and lamp resistances, so the current supplied by the battery is lower than in the parallel arrangement.

Examiner tips

  • Use the command word ‘Explain’ – describe the situation and give reasons.
  • Show the voltage division in series and the full voltage in parallel.
  • Mention the effect on brightness and total current explicitly.
  • Use correct terminology: series, parallel, voltage, current, resistance.

Common mistakes

  • Saying the lamp is brighter in series – it is actually dimmer.
  • Confusing current with voltage – the battery voltage is the same in both circuits.
  • Omitting that the total current is higher in parallel because of two paths.

Mark scheme (4 marks)

  1. In the series circuit the same current passes through both the buzzer and the lamp, so the voltage is shared (split) between them
  2. In the parallel circuit each component receives the full battery voltage, so the lamp is brighter in parallel than in series
  3. In the parallel circuit the current from the battery is greater because there are two separate paths for the current to flow through
  4. In the series circuit the total current from the battery is lower because the buzzer and lamp together provide more resistance to the current than either component alone

Key terms in this question

current

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