A household has two lamps connected in a parallel circuit. Describe how the potential difference across each lamp and the current through each lamp compare to the values in the rest of the circuit.

AQA GCSE Physics (8463) — 4.2.2 Series and parallel circuits · Describe · 4 marks · View as Markdown

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

A household uses two lamps connected in parallel to the mains supply. Each lamp has a different resistance.

Model answer (4 marks)

The potential difference across each lamp is the same as the potential difference of the power supply and each other.
The current through each lamp can be different because the lamps have different resistances.
The total current from the supply equals the sum of the currents through each lamp.
The total resistance of the parallel circuit is less than the resistance of either individual lamp.

Examiner tips

  • Use the word ‘same’ to link the potential differences. Mention that different resistances give different currents. State the current addition rule. Recall that 1/R_total = 1/R1 + 1/R2 to justify lower total resistance.

Common mistakes

  • Confusing series and parallel relationships. Saying the currents are the same. Forgetting that the total resistance is lower than each lamp’s resistance.

Mark scheme (4 marks)

  1. The potential difference across each lamp is the same as the potential difference of the power supply / each other
  2. The current through each lamp can be different (because the lamps have different resistances)
  3. The total current from the supply equals the sum of the currents through each lamp
  4. The total resistance of the parallel circuit is less than the resistance of either individual lamp

Key terms in this question

parallel · potential difference · current

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