Question 1

What is the difference between calorie and Calorie?

Accepted Answer

Small calorie (cal) = 4.184 J. Food Calorie (Cal, kcal) = 1000 cal = 4.184 kJ. Context matters!

Question 2

Why do food labels use Calories?

Accepted Answer

Food energy is large. Saying 200,000 calories would be confusing. 200 Calories (kcal) is clearer.

Question 3

What's the difference between energy and power?

Accepted Answer

Energy (joules, kWh) is total work done. Power (watts) is energy per unit time. A 100W bulb for 10 hours = 1 kWh of energy.

Question 4

Why are there so many energy units?

Accepted Answer

Different fields developed their own: BTU for heating, calories for nutrition, joules for physics, kWh for electricity billing.

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