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S1 Science: Energy Forms and Conversion (Paper 2: intermediate)
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S1 Science: Energy Forms and Conversion (Paper 2: intermediate)
The second paper drills power and bills: watts into kilowatts, minutes into hours, then multiply by the tariff.
Direct answers Write the unit before the number each time, and a correct unit usually brings a correct answer.
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: S1 Science: Energy Forms and Conversion |
| Level | S1 Science |
02 Questions (10 items)
- FoundationWhat is the definition of power?
- FoundationHow many watts are there in 1 kW?
- FoundationIs the kilowatt hour a unit of energy or of power?
- IntermediateA 2 000 W appliance runs for 30 minutes. How many kWh does it use?
- IntermediateA machine is 60 per cent efficient and takes in 800 J. What is the useful output?
- IntermediateA machine gives 45 J of useful energy at 90 per cent efficiency. What is the input?
- ChallengeA 1 500 W kettle runs for 40 minutes and electricity costs $1.2 per kWh. What is the cost?
- ChallengeA 100 W fan runs for 5 hours at $1.2 per kWh. What is the cost?
- ChallengeA 40 W bulb is replaced by a 10 W LED of the same brightness and used 5 hours a day. How many kWh are saved a day?
- Error redoA student works out that 1 000 W for 2 hours uses 2 000 kWh. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | The rate of energy conversion, that is the joules converted each second | Power tells how fast and energy tells how much, and the two carry different units. |
| 2 | 1 000 W | A kilowatt is one thousand watts, and electricity sums start by turning watts into kilowatts. |
| 3 | A unit of energy | One kilowatt hour is the energy used by 1 kW in one hour, which equals 3 600 000 J. |
| 4 | 1 kWh | Half an hour is 0.5 hour, and 2 times 0.5 gives 1 kWh. |
| 5 | 480 J | 60 per cent of 800 J is 480 J. |
| 6 | 50 J | 45 divided by 90 per cent gives 50 J, so the way back is division. |
| 7 | $1.20 | That is 1.5 kW for two thirds of an hour, giving 1 kWh and therefore $1.20. |
| 8 | $0.60 | 100 times 5 gives 500 Wh which is 0.5 kWh, and 0.5 times 1.2 is $0.60. |
| 9 | 0.15 kWh | That saves 30 W, and 30 times 5 gives 150 Wh or 0.15 kWh, worth about $0.18. |
| 10 | The division by 1 000 was skipped, so the answer is 2 kWh | Watts must be turned into kilowatts first, and 1 kW for 2 hours is 2 kWh. |
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.
The intermediate paper keeps power and energy apart: power is the joules converted each second, electricity is billed in kilowatt hours, and the sum is watts times hours divided by one thousand.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.