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S5 Physics: Circuits Practice Paper 1
S5 Physics: Circuits Practice Paper 1
Paper one covers series and parallel equivalents, I = V / R and power, then voltage division, branch currents and a parallel-then-series simplification, followed by a three-resistor parallel network and a mixed circuit, ending with the add-parallel-resistances trap.
Quick answer 10 ohm, 2 ohm, 3 A, 10 V and 20 W, 1 A and 3 V, 2.4 ohm and 5 A, 2 A, 1 ohm and 6 A, 2.4 A and 19.2 V, and 9 ohm being wrong.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | 25 minutes |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S5 Physics: Circuits – Tutor Lesson Plan |
| Level | S5 |
02 Questions (10 items)
- FoundationTwo resistors of 4 ohm and 6 ohm are joined in series. Find the equivalent resistance.
- FoundationA 6 ohm and a 3 ohm resistor are connected in parallel. Find the equivalent resistance.
- FoundationA 4 ohm resistor is connected across a 12 V supply. Find the current.
- FoundationA current of 2 A flows through a 5 ohm resistor. Find the voltage across it and the power.
- IntermediateA 12 V supply drives 3 ohm and 9 ohm in series. Find the current and the voltage across the 3 ohm resistor.
- IntermediateA 6 ohm and a 4 ohm resistor in parallel are connected to 12 V. Find the equivalent resistance, total current and branch currents.
- IntermediateTwo 8 ohm resistors are in parallel and a 2 ohm resistor is in series with them; the whole group is across 12 V. Find the total current.
- ChallengeResistors of 2 ohm, 3 ohm and 6 ohm are in parallel across 6 V. Find the equivalent resistance, total current and the three branch currents.
- ChallengeA 24 V supply is connected to 8 ohm in series with a parallel pair of 6 ohm and 3 ohm. Find the total current, the voltage across 8 ohm, the voltage across the pair and both branch currents.
- Error redoA student adds parallel 6 ohm and 3 ohm to get 9 ohm. What is the correct value and where is the mistake?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 10 ohm (4 + 6) | In series the current has one path only, so resistances add. |
| 2 | 2 ohm (1/R = 1/6 + 1/3) | A parallel combination is always smaller than the smallest resistor in it. |
| 3 | 3 A (12 / 4) | Use I = V / R. |
| 4 | Voltage 10 V, power 20 W (P = I squared R) | Power may be found from P = VI or I squared R; both give the same answer. |
| 5 | Current 1 A, voltage across 3 ohm is 3 V | The series current is the same everywhere and the voltage splits in proportion to resistance. |
| 6 | Equivalent 2.4 ohm, total 5 A, branches 2 A and 3 A | Branches share the same voltage and carry currents inversely proportional to their resistances. |
| 7 | 2 A (8 parallel 8 is 4 ohm, plus 2 ohm gives 6 ohm, 12 / 6) | Simplify the parallel part first, then add the series resistance. |
| 8 | Equivalent 1 ohm, total 6 A, branches 3 A, 2 A and 1 A | Here 1/R = 1/2 + 1/3 + 1/6 = 1, so the equivalent resistance is exactly 1 ohm. |
| 9 | Total 2.4 A, 19.2 V across 8 ohm, 4.8 V across the pair, branches 0.8 A and 1.6 A | The pair is 2 ohm so the total is 10 ohm; the two voltages must add to 24 V. |
| 10 | Correct value is 2 ohm; parallel resistors add as reciprocals, not directly | Only series resistances add directly; a parallel combination is always smaller than its smallest resistor. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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