Question

Compare the energy consumption of two commonly used items in the household. Calculate the energy used by a 1.40 kW toaster oven, Wtoaster , which is used for 5.40 minutes , and then calculate the amount of energy that an 11.0 W compact fluorescent light (CFL) bulb, Wlight , uses when left on for 10.50 hours .

Answer 1

To compare the energy usage, a 1.40 kW toaster oven used for 5.40 minutes consumes 0.126 kWh, while an 11.0 W CFL bulb left on for 10.50 hours uses 0.1155 kWh.

Step-by-step explanation:

Comparing the energy consumption of two household items involves looking at their power ratings and how long they are used. To calculate the energy used by a 1.40 kW toaster oven (Wtoaster) for 5.40 minutes, we convert minutes to hours (5.40 min = 0.09 hours) and use the formula Energy (kWh) = Power (kW) × Time (h). The calculation is then 1.40 kW × 0.09 h = 0.126 kWh. For an 11.0 W compact fluorescent light (CFL) bulb (Wlight) on for 10.50 hours, the energy usage is 11 W × 10.50 h = 115.5 Wh, which is 0.1155 kWh (since 1 kW = 1000 W).

Answer 2

Energy = (power) x (time)

-- For the toaster:

Power = 1.4 kW = 1,400 watts

Time = 5.4 minutes = 324 seconds

Energy = (1,400 W) x (324 s) = 453,600 Joules

-- For the CFL bulb:

Power = 11 watts

Time = 10.5 hours = 37,800 seconds

Energy = (11 W) x (37,800 s) = 415,800 Joules

-- The toaster uses energy at 127 times the rate of the CFL bulb.

-- The CFL bulb uses energy at 0.0079 times the rate of the toaster.

-- The toaster is used for 0.0086 times as long as the CFL bulb.

-- The CFL bulb is used for 116.7 times as long as the toaster.

-- The toaster uses 9.1% more energy than the CFL bulb.

-- The CFL bulb uses 8.3% less energy than the toaster.