Distinguish power from energy
See this course’s project requirements
A desk-based household energy comparison with checked kWh estimates, usage assumptions and a safe no-installation conservation recommendation.
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What to include
- Calculate power-time energy with explicit units.
- Complete a quantity-aware 30-day device table.
- Separate ratings, measurements and standardized estimates.
- Compare matched lighting output and calculate differences.
- Recommend an existing-control action preserving essential services.
- Recalculate the final comparison and retain evidence limits.
Review and revise
Use these criteria to check your work and choose what to improve.
- Method: applies the course-specific rules to the supplied cases with visible intermediate work.
- Accuracy: results agree with the stated facts, units, boundaries and independent checks.
- Reasoning: explains why the result follows and identifies a limitation or unresolved question.
- Transfer: completes changed cases and revises the final project when a relevant assumption changes.
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The idea in everyday life
Fictional constant-power cards: lamp A uses 60 W for 5 hours; device B uses 1,500 W for 0.1 hour. These are supplied operating values, not instructions to inspect equipment.
Power is the rate of energy transfer; watts describe power. Energy accumulates over time: for constant power, watt-hours equal watts times hours. One kilowatt is 1,000 watts, and one kilowatt-hour is 1,000 watt-hours. A high-power device used briefly can consume less energy than a lower-power device used for many hours.
Distinguish power from energy — worked practice
Power is the rate of energy transfer; watts describe power. Energy accumulates over time: for constant power, watt-hours equal watts times hours. One kilowatt is 1,000 watts, and one kilowatt-hour is 1,000 watt-hours. A high-power device used briefly can consume less energy than a lower-power device used for many hours.
Fictional constant-power cards: lamp A uses 60 W for 5 hours; device B uses 1,500 W for 0.1 hour. These are supplied operating values, not instructions to inspect equipment.
1. 1. Label
Identify power and duration on both cards.
You should see: A: 60 W and 5 h; B: 1,500 W and 0.1 h.
2. 2. Multiply
Find each energy amount in watt-hours.
You should see: A: 300 Wh; B: 150 Wh.
3. 3. Convert
Divide watt-hours by 1,000.
You should see: A: 0.3 kWh; B: 0.15 kWh.
4. 4. Compare
Explain why wattage alone reverses the energy ranking.
You should see: B has greater power but half A’s energy over these durations.
What to finish
A two-device power/time/energy comparison with labeled units.
Watch for this
Energy depends on both power and time. The supplied lamp operates long enough to exceed the brief high-power device’s energy.
How can I tell I understand it?
Calculate a changed constant-power case without confusing watts and kilowatt-hours.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
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Source & access notes · checked 2026-10-01
Web open/search showed the official page, its topic heading and relevant concept description. This is a content/source check, not a provider endorsement.
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