(a) Determine the resistance of the refrigerator:
R=IV=5240=48 Ω.(b) (i) Calculate the electrical power in the refrigerator when plugged to the 220 V power outlet:
Pr=RV2=482202=1000 W.
(b) (ii) Calculate the input power of each light bulb:
Pb=ηPrated=0.830=37.5 W.
(b) (iii) At what rate is energy consumed by the restaurant?
The rate of energy consumption is energy per unit time, or power:
Ptotal=5⋅37.5+1000+1500=2690 W.
(c) If the restaurant needs a single fuse to protect all its devices, recommend the rating of the fuse in amperes is
I=VPtotal=2202690=12.2 A.
(d) Calculate the daily energy consumption of the restaurant.
The bulbs work 12 h, refrigerator works 24 h, electric cooker works 5 hours a day:
E=5Pbtb+Prtr+Pctc==5⋅100037.5⋅12+1⋅24+1.5⋅5=33.8 kWh.
(e) If PHCN charges ₦32 per kWh, calculate the monthly (4 weeks) bill.
The restaurant works six days a week, there are 4 weeks (24 days) in a month, the monthly bill is
Bm=NEc=24⋅33.8⋅32=25958 ₦/month.
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