Question

In May you used 900 ​kilowatt-hours of energy for electricity.

a. Calculate the total electrical energy use in joules.
b. Calculate your average power use in watts.
c. Assume that your power supplier generates electricity by burning oil. Note that 1 liter of oil releases 12 million joules of energy. How much oil is needed to generate the electricity you​ use? Give your answer in both liters and gallons.

a. The total electrical energy use was ___ joules.
​(Type an integer or a​ decimal.)

b. The average power use is_____ watts.
​(Round to the nearest whole number as​ needed.)

c. To generate the electricity you​ used, _____L is needed.
​(Round to the nearest whole number as​ needed.)

To generate the electricity you​ used, _____ gal is needed.
​(Round to two decimal places as​ needed.)

Answer 1

a) "The total electrical energy use was 3,240,000,000 joules."

b) "The average power use is 1210 watts."

c)

Part 1: "To generate the electricity you​ used, 810 L is needed."

Part 2: "To generate the electricity you​ used, 214.00 gal is needed."

Explanation:

a)

1 kilowatt-hours =
`3.6x10^6` joules

Converting 900 kilowatt-hours to joules, we have:

`900*(3.6*10^6)=3.24*10^9` joules, or

Total Electrical Energy use = 3,240,000,000 joules

"The total electrical energy use was 3,240,000,000 joules."

b)

The month of May has 31 days and 1 day is 24 hours. So May has:

31*24=744 hours

Now, we divide 900 kW-hr by the number of hours in the month (744 hrs) to get average power use:

`(900)/(744)=1.21` kW. Since 1000 Watts = 1 kW, we multiply this by 1000 to get the answer in Watts:

1.21 * 1000 = 1210 Watts

"The average power use is 1210 watts."

c)

Part 1:

The conversion efficiency of most generating stations is 33%. So we need to multiply the total electrical energy use (in joules) by a factor of 3 to get the amount of joules required. So:

(3.24 * 10^9)*3 = 9.72 * 10^9 joules

We divide this by 12 million joules to get the number of liters:

`(9.72*10^9)/(12*10^6)=810`

So, 810 liters is needed

"To generate the electricity you​ used, 810 L is needed."

Part 2:

We know that 0.2642 gallons is equal to 1 liters. To get the number of gallons needed, we multiply 810 by 0.2642. So:

810 * 0.2642 = 214.00 gallons

"To generate the electricity you​ used, 214.00 gal is needed."