(a) What is the commercial unit of energy ? Give its relationship with SI unit of energy. (b) An electric bulb of 60 W is lighted for 10 hours everyday. How many units of electrical energy is consumed by this bulb in one day?


#1

(a) The commercial unit of energy is kilowatt hour (kW h).
1 kW h = 3.6 x 10^6 J

(b) Given P = 60 W,
t = 10 h,
W = ?
W = P x t
= 60 x 10
= 600 W h
= 0.6 kW h.