Question 1Warm-upFoundation
A 4 Ω and a 6 Ω resistor are in series. What is the total resistance?
In series, resistances add.
Worked solution
- Ω
Answer: Ω
GCSE & IGCSE physics practice
Series and parallel circuits questions and answers
In a series circuit the current is the same everywhere, the potential difference is shared, and resistances add: . In a parallel circuit each branch gets the full potential difference, the branch currents add up to the total, and the total resistance is less than the smallest branch resistance.
8 questions · Foundation and Higher tier · Every answer is checked as you type it, with a full worked solution. Updated .
Where series and parallel circuits comes up
| GCSE (AQA) | Physics and Combined Science, Foundation and Higher: series rules and R total = R1 + R2; parallel rules, and know (qualitatively) that two resistors in parallel have less resistance than the smaller one. |
|---|---|
| Cambridge IGCSE (0625) | Core: combined resistance of resistors in series, and that two resistors in parallel have less resistance than either. Supplement: calculate the combined resistance of two resistors in parallel. |
The method
- Series: same current everywhere; potential differences add up to the supply; R total = R1 + R2.
- Parallel: same potential difference across each branch; branch currents add up to the total current.
- Use V = IR for each component.
- Two resistors in parallel (Cambridge Extended): 1/R = 1/R1 + 1/R2.
Series and parallel circuits questions
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Warm-up
Question 2Warm-upFoundation
In a parallel circuit, one branch has 0.4 A and the other has 0.6 A. What is the current from the cell?
Branch currents add up to the total.
Worked solution
- A
Answer: A
Exam-style
Question 3Exam-styleFoundation
A 12 V battery is connected to a 4 Ω and an 8 Ω resistor in series. Calculate the current.
Find the total resistance first.
Worked solution
- Ω
- A
Answer: A
Question 4Exam-styleFoundation
Two lamps are in series with a 9 V battery. The potential difference across one lamp is 3.5 V. What is it across the other?
In series, the potential differences add up to the supply.
Worked solution
- V
Answer: V
Question 5Exam-styleFoundation
A 12 Ω resistor is in one branch of a parallel circuit connected to a 6 V battery. Calculate the current in that branch.
Each parallel branch has the full 6 V.
Worked solution
- A
Answer: A
Question 6Exam-styleFoundation
A 3 Ω and a 6 Ω resistor are in series with a current of 1.5 A. Calculate the potential difference across the 6 Ω resistor.
Same current through each: V = IR for that resistor.
Worked solution
- V
Answer: V
Challenge
Question 7ChallengeFoundation
Two 10 Ω resistors are connected in parallel. Which could be their total resistance?
In parallel, the total resistance is less than either resistor.
Worked solution
- The total must be less than 10 Ω, so it's 5 Ω.
- (Check: , so Ω.)
Answer: Ω: in parallel the total is less than the smallest resistor
Question 8ChallengeHigher
A 6 Ω and a 3 Ω resistor are connected in parallel. Calculate their combined resistance. (Cambridge Extended)
1/R = 1/R1 + 1/R2.
Worked solution
- Ω
Answer: Ω
Common mistakes
- Adding resistances that are in parallel.
- Thinking current is used up along a series circuit.
- Giving the total current through just one branch.
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Sources
The questions are our own. The “where it comes up” notes are from each board's published specification, checked on 27 October 2026:
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