Based on what you’ve just read, answer the following questions.
- Between the hours of 6:00 p.m. and 11:00 p.m., John has agreed to clean the
oven. Meanwhile Mary is watching television in the livingroom and has two
lamps burning. Adam is reading in his bedroom. Let’s see how many watts
all of these devices use.
- Calculate the total number of watts used for each device. Write
your answers in the “Total Watts” column.
- Add up the watts to find the total watts used. Write your answer
in the “Total Watts” column.
| Electrical device |
Number of Watts |
Total Watts |
| 1 kitchen light |
100 watts |
|
| 2 livingroom lamps |
100 watts each |
|
| 1 television |
120 watts |
|
| 2 bedroom lamps |
40 watts each |
|
| |
|
|
| Total number of
watts |
|
|
- Now calculate how many kilowatts that would be.
watts ÷ 1,000 = kilowatts
- Next, calculate the number of kilowatt hours.
kilowatts x 5 hours = kilowatt hours
- Finally, calculate the cost of electricity for a 5 hour period at 7¢
per kilowatt-hour.
kilowatt hours x $0.07 = $
- How much would it cost if the same electrical devices were to run
for 5 hours each day in the month of September? (Remember that
September has 30 days!)
Notice that in Question 3 we did not include the cost of running the
refrigerator or other major appliances. Electrical appliances can use large amounts of electrical power. For example, if John was cleaning a self-cleaning oven, it would draw about 2600 watts! That’s 2.6 kilowatts. At 7¢ a kilowatt-hour, that’s 18.2¢ for every hour that the oven is operating.