(a) A particular household uses a 1.7-kW heater 2.9 h/day (\"on\" time), four 99
ID: 1410854 • Letter: #
Question
(a) A particular household uses a 1.7-kW heater 2.9 h/day ("on" time), four 99-W lightbulbs 4.5 h/day, a 3.4-kW electric stove element for a total of 1.5 h/day, and miscellaneous power amounting to 1.8 kWh/day. If electricity costs $0.15 per kWh, what will be their monthly bill (assume 1 month = 30 days)?
........................ dollars
(b) How much coal (which produces 7000 kcal/kg) must be burned by a 35%-efficient power plant to provide the yearly needs of this household (1 year = 365 days, not 12x30 days)?
.........................kg
Explanation / Answer
a) Energy consumed per day = 1.7*2.9 kWh + 4*0.099*4.5 kWh +3.4*1.5 kWh + 1.8 kWh
= 13.612 kWh
Cost per month = 30*daily consuption*cost = 30*13.612*0.15 = 61.254 dollars
b) mass to be burnt = 365* 13.612 kWh /[7000 kcal/kg *0.35]
= 1 744.8 kg
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