A Levels Physics (9702)•9702/13/M/J/18

Explanation
Equivalent resistance determines battery current via Ohm's law
Steps:
- Calculate required equivalent resistance: R_eq = V / I = 6 V / 0.67 A = 9 Ω.
- Two 6 Ω resistors in parallel give 3 Ω; add third in series for 3 Ω + 6 Ω = 9 Ω.
- Total current through battery is V / R_eq = 6 V / 9 Ω = 0.67 A.
- Verify other configurations yield different currents.
Why A is correct:
- Configuration A has two resistors in parallel (3 Ω) in series with one (6 Ω), yielding R_eq = 9 Ω and I = 0.67 A per Ohm's law.
Why the others are wrong:
- B (all in series): R_eq = 18 Ω, I = 0.33 A.
- C (all in parallel): R_eq = 2 Ω, I = 3 A.
- D (two in series parallel with one): R_eq = 4 Ω, I = 1.5 A.
Final answer: A
Topic: Practical circuits
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