A string of Christmas tree lights is wired in series. When one bulb breaks, all the other lights go out. Explain why all the lights go out when one bulb breaks in a series circuit.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A string of Christmas tree lights contains ten identical bulbs connected in series to a mains supply.
Model answer (4 marks)
In a series circuit there is only one path for the current to flow. When one bulb breaks the circuit is broken, creating a gap. Current cannot flow through a broken circuit, so no current reaches the remaining bulbs. With no current, the other bulbs do not light up.
Examiner tips
- Use the term ‘series circuit’ and ‘single path’. Mention the circuit becomes incomplete. State that current cannot flow and that the other bulbs receive no current. Keep each point brief and to the point.
Common mistakes
- Confusing series with parallel, or saying the bulbs are ‘in parallel’.
- Failing to explain that the circuit is incomplete and current stops.
Mark scheme (4 marks)
- In a series circuit there is only one path for the current to flow
- When the bulb breaks, the circuit becomes incomplete / the circuit is broken / there is a gap in the circuit
- Current cannot flow through a broken/incomplete circuit
- With no current flowing, the remaining bulbs receive no current and so do not light up
Key terms in this question
Related
- All Eduqas GCSE Physics revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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