Final answer:
To find out how many calories are equivalent to 3 kilowatt-hours of electrical energy, convert the energy to joules and then to calories. The conversion results in approximately 3,000,000 calories, which corresponds to Option A.
Step-by-step explanation:
The question we are addressing is about converting electrical energy, measured in kilowatt-hours, to thermal energy, measured in calories. To determine how many calories of heat may be obtained from 3 kilowatt-hours of electrical energy, we use the conversion relationship that 1 kilowatt-hour (kWh) is equivalent to 3.6 × 106 joules (J). Since 1 food calory C is equivalent to 4,184 Joules, we can calculate the conversion.
First, we convert 3 kWh to joules:
3 kWh × 3.6 × 106 J/kWh = 1.08 × 107 J. Then, we convert joules to calories:
1.08 × 107 J × (1 cal / 4.184 J) = 2.58 × 106 calories. As 1 kcal is 1,000 calories, this is equivalent to 2,580 kcal.
The correct answer is Option A, as 2,580 kcal is equivalent to 2,580,000 calories, which is best rounded to 3,000,000 calories, given the options available.