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S2 Science: Electric Circuits, Current, Voltage and Resistance (Paper 4: mistake clinic)
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S2 Science: Electric Circuits, Current, Voltage and Resistance (Paper 4: mistake clinic)
This paper targets the four recurring errors: reversing the Ohm law operations, adding parallel resistances, leaving watt hours unconverted, and believing a resistor consumes current. Each question tests a single cause.
Direct answers Answers in order: equal series current and equal parallel voltage, 30 V, 4 A, 4 ohms, 4 ohms, 0.1 kWh, 2 A, 0.15 dollars, 4 ohms, no.
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: S2 Science: Electric Circuits, Current, Voltage and Resistance |
| Level | S2 Science |
02 Questions (10 items)
- FoundationIn one line: in series do we fix current or voltage, and in parallel?
- FoundationA 10 ohm resistor carries 3 A. What is the voltage across it?
- FoundationA 24 V supply is connected across a 6 ohm resistor. What current flows?
- IntermediateTwo 8 ohm resistors are in parallel. What is the total resistance?
- IntermediateA 5 ohm and a 20 ohm resistor are in parallel. What is the total resistance?
- IntermediateA 40 W lamp runs for 2.5 hours. How many units does it use?
- ChallengeTwo 3 ohm resistors are in series across 12 V. What is the current?
- ChallengeAt 1.5 dollars per unit, what is the charge for 0.1 kWh?
- ChallengeMistake clinic: with 12 V and 3 A a student writes R = V times I and gets 36 ohms. What is correct?
- Error redoCan one part of a series wire carry more current than another part?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Series has the same current everywhere; parallel has the same voltage across every branch | Hold on to that line and derive the rest from V = IR. |
| 2 | 30 V | Ten times three is thirty. |
| 3 | 4 A | Twenty-four divided by six is four. |
| 4 | 4 ohms | Two equal resistors in parallel halve the value, eight over two is four. |
| 5 | 4 ohms | One over one fifth plus one twentieth is four ohms. |
| 6 | 0.1 kWh | Forty times two and a half is a hundred watt hours, or 0.1 kilowatt hours. |
| 7 | 2 A | Total resistance is six, twelve over six is two. |
| 8 | 0.15 dollars | 0.1 times 1.5 is 0.15. |
| 9 | 4 ohms | R is V divided by I, twelve over three is four; multiplying reverses Ohm law. |
| 10 | No, series current is equal everywhere | Any difference would pile charge up on the way, which contradicts conservation. |
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.
Keep an error log with three columns: question, cause, corrected working. The causes are usually a reversed formula, an unconverted unit, or series mixed up with parallel.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.