Electronic devices use electrical energy even when they are on standby. Calculate the percent of energy used per day for the following entertainment equipment in the standby mode assuming that they are plugged in all the time.
Device
Standby Power
Power when on
Hours on per day
DVD player
1 W
75 W
4
TV
2 W
100 W
6
Tuner
1 W
150 W
4
A) 0.45%
B) 1.1%
C) 4.8%
D) 5.1%
E) None of these is correct.

Question

Quizplus · Accepted Answer

To calculate the energy used in standby mode, we can use the formula:

Energy used in standby = Standby power x Hours on per day

Then, to calculate the percent of energy used per day in standby mode:

Percent of energy used per day = Energy used in standby / (Power when on x Hours on per day) x 100%

For the DVD player: 
Energy used in standby = 1 W x 4 hours = 4 Wh
Percent of energy used per day = 4 Wh / (75 W x 4 hours) x 100% = 1.07%

For the TV: 
Energy used in standby = 2 W x 6 hours = 12 Wh
Percent of energy used per day = 12 Wh / (100 W x 6 hours) x 100% = 2%

For the Tuner: 
Energy used in standby = 1 W x 4 hours = 4 Wh
Percent of energy used per day = 4 Wh / (150 W x 4 hours) x 100% = 0.67%

Adding up the percentages, we get: 
1.07% + 2% + 0.67% = 4.74%

So, the closest answer is C) 4.8%

Electronic Devices Use Electrical Energy Even When They Are on Standby