🔌 Energy & Power
Electricity, fuel, engines, and energy consumption measurements.
Energy & Power Overview ⚡
Energy measures the ability to do work or produce heat, while power measures how fast energy is used or produced.
This section covers common units of energy and power, their conversions, and practical examples from everyday life.
Key Facts
- 1 kilowatt-hour (kWh) = 3.6 million joules (J)
- 1 horsepower (hp) ≈ 746 watts (W)
- Power (W) = Energy (J) ÷ Time (s)
- Energy units vary based on context: joules for physics, kWh for electricity, kcal for food energy, and BTU for heating/cooling
Formulas
Energy (J) = Power (W) × Time (s)- Calculate energy from power and timePower (W) = Energy (J) ÷ Time (s)- Calculate power from energy and time1 kWh = 3.6×10^6 J- Convert kilowatt-hours to joules1 hp ≈ 746 W- Convert horsepower to watts
Energy & Power Examples
- A 100 W light bulb running for 2 hours uses 200 Wh → 720,000 J
- Laptop battery: 50 Wh → 180,000 J
- Car engine: 10 hp ≈ 7,460 W
- Cup of coffee: 70 kcal → 292,880 J
FAQs
Why do we have multiple energy units?
Different units suit different contexts — physics experiments use joules, household electricity uses kWh, food uses kcal, and HVAC uses BTU.
How does power relate to energy?
Power is the rate of energy use: higher power devices consume energy faster.
Can I convert between all energy units?
Yes — with formulas and conversion factors, you can translate between J, Wh, kWh, BTU, and kcal.