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Resistance and Circuits Paper 2: Intermediate
Resistance and Circuits Paper 2: Intermediate
Applying the formulas to real components: how length and thickness change resistance, mixed series and parallel, branch currents, rated against actual values, and electricity cost.
Direct answers Answers and explanations for all ten questions
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: DSE Physics Resistance and Circuits |
| Level | Paper 2 (intermediate) |
02 Questions (10 items)
- FoundationA wire of the same material and cross-section is doubled in length from 1 m to 2 m. If it was 8 ohms, what is it now?
- FoundationA wire keeps its length but doubles its cross-sectional area, its resistance having been 12 ohms. Find the new resistance.
- FoundationResistors of 2, 3 and 5 ohms are in series across 20 V. Find the total resistance and the current.
- IntermediateA 12 ohm and a 4 ohm resistor are joined in parallel. Find the total resistance.
- IntermediateA 6 ohm and a 3 ohm resistor are in parallel and the total current is 2.4 A. Find the voltage across them and the current in each branch.
- IntermediateA 2 000 W kettle runs for 15 minutes. Find the energy used in kWh.
- ChallengeThe current against voltage graph of a metal conductor is a straight line through the origin, and 0.4 A corresponds to 8 V. Find the resistance and state what the slope means.
- ChallengeA lamp is rated 12 V and 24 W. Find its normal current and resistance.
- ChallengeA 12 V supply is connected across 8 ohm and 4 ohm resistors in series. Find the voltage across each.
- Error redoError clinic: a student claims a parallel total exceeds the largest branch, writing 16 ohms for 12 and 4. Find the correct total and the mistake.
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 16 ohms: resistance is proportional to length, so doubling the length doubles the resistance. | Shortening or lengthening a wire scales its resistance with length while material and thickness stay fixed. |
| 2 | 6.0 ohms: resistance is inversely proportional to area, so double the area and halve the resistance. | A thicker wire passes current more easily, so doubling the area halves the resistance. |
| 3 | The total is 10 ohms and the current is 2.0 A. | Add the resistances first, then divide the supply voltage by the total. |
| 4 | 3.0 ohms: one over R is one twelfth plus one quarter, giving one third. | For two branches the product over the sum works as well: 12 times 4 divided by 16. |
| 5 | The total is 2.0 ohms, the voltage 4.8 V, and the branch currents 0.7999999999999999 A and 1.5999999999999999 A. | Parallel branches share the voltage and split the current in inverse proportion to resistance. |
| 6 | 0.5 kWh: 2 kW for a quarter of an hour. | Minutes must be converted to hours first, or the result is sixty times too large. |
| 7 | 20.0 ohms: the slope of voltage against current is the resistance. | The slope of V against I is the resistance, while I against V would give conductance. |
| 8 | The current is 2.0 A and the resistance 6.0 ohms, from P = VI and then R = V divided by I. | Rated values hold only at the rated voltage; a different voltage needs a fresh calculation. |
| 9 | The 8 ohm resistor takes 8.0 V and the 4 ohm resistor 4.0 V, at a current of 1 A. | Series voltages divide in proportion to resistance and must add back to the supply voltage. |
| 10 | The correct total is 3.0 ohms: a parallel total is always below the smallest branch, and 16 ohms treats them as series. | A quick check: the answer must be under 4 ohms, so anything larger is already wrong. |
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.
When a wire doubles in length or area, write the proportion first and then multiply or divide; the answer cannot then be inverted.Tutor Registration →
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