Question

In an office a tube light of 40w, a fan of 75w and a cooler of 150w have been installed. if all these appliances are used for 8hrs a day. calculate the energy consumed for a week in terms of commercial unit of energy.

Answer 1

given that
power of tube light = 40 watt 
power of fan = 75 watt 
power of cooler = 150 watt

total energy consume =total power x time 
= (40 + 75 + 150)watt x 8 hour 
=265 watt x (8 x 60 x 60 ) sec 
=265 x 8 x 3600 joule 
=7632000 joule 
we know that  .
1 kwh = 3.6 x 10^6 joule 
hence 
7632000 joule = 7632000/3.6 x10^6 kwh 
= 2.12 kwh