中文（繁體）
中文（简体）
English
Primary General Studies: Energy and Saving Power (Paper 4 (error clinic))
Primary General Studies: Energy and Saving Power (Paper 4 (error clinic))
Paper four re-drills four common errors: brightness equals consumption, off button equals no power, label grades, and watt hours not converted into units, using a fresh set of numbers.
Direct answers Write the unit first in every question, then check at the end whether the answer is in watt hours, units or kilograms.
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: Primary General Studies: Energy and Saving Power |
| Level | parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety |
02 Questions (10 items)
- FoundationWhy does an LED use less power than a filament bulb?
- FoundationWhich saves more: pressing the off button or unplugging?
- FoundationWhat does grade one on an energy label mean?
- IntermediateA 9 watt LED runs for 5 hours. How many watt hours does it use?
- IntermediateA 60 watt filament bulb runs for 5 hours. How many watt hours does it use?
- IntermediateHow many watt hours apart are they?
- ChallengeHow many units does that gap come to over 30 days?
- ChallengeAt 0.7 kg per unit, how many grams of carbon dioxide do 7.65 units emit?
- ChallengeSwitching from 60 watts to 9 watts cuts energy by how many percentage points?
- Error redoA classmate says standby is only a few watts and cannot affect the bill. Is that right?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | For the same brightness, its power rating is much lower. | The key to saving is the wattage, not the price of the lamp. |
| 2 | Unplugging or switching off the supply, because it avoids standby power. | An appliance with standby still draws power after the button is pressed. |
| 3 | It is the most efficient of its kind. | The smaller the grade number, the less energy it needs for the same job. |
| 4 | 45 watt hours. | 9 × 5 = 45 watt hours. |
| 5 | 300 watt hours. | 60 × 5 = 300 watt hours. |
| 6 | 255 watt hours. | 300 − 45 = 255 watt hours. |
| 7 | 7.65 units. | 255 × 30 = 7650 watt hours, which is 7.65 units. |
| 8 | 5355 grams. | 7.65 × 0.7 = 5.355 kg, which is 5355 grams. |
| 9 | 85 percentage points. | (60 − 9) ÷ 60 × 100 = 85, so the cut is 85 percentage points. |
| 10 | No. Five watts for 20 hours a day is 100 watt hours, which makes 3 units a month. | Small power over a long time still shows up on the bill. |
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.
With all four done, go back to the chapter page and revise the three parts of a closed circuit plus three safety habits.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.