Final answer:
The energy in a generic $10 pizza containing about 2500 kcal translates to 10460000 Joules or 10.46 MJ. When comparing its energy cost with electricity, electricity is the cheaper form of energy.
Step-by-step explanation:
Given that one Calorie (with a capital C) is equivalent to a kilocalorie (kcal), and one kilocalorie is equivalent to 4184 joules, you can calculate the number of joules in a slice of pizza with known caloric content. For example, if a generic $10 pizza might contain approximately 2500 kcal, use the following conversion: 1 kcal = 4184 J.
To find the total energy in joules, multiply the energy in kilocalories by the conversion factor:
Energy in joules = 2500 kcal × 4184 J/kcal = 10460000 J or 10.46 MJ (MegaJoules).
Comparing the cost of this energy with electricity, we convert kilojoules to kilowatt-hours (kWh). There is a relationship of 1 kWh = 3.6 x 10^6 J, hence the energy in kWh is:
Energy in kWh = 10460000 J / (3.6 x 10^6 J/kWh) = 2.905 kWh.
At an electrical cost of $0.15 per kWh, the cost in electrical terms would be:
Cost = 2.905 kWh × $0.15/kWh = $0.436.
Since the pizza costs $10, and the equivalent amount of energy in electrical terms costs about $0.44, electricity is a much cheaper form of energy than the energy obtained from the pizza when considering the raw energy content.