Question

(a) Derive the relation between commercial unit of energy (kWh) and SI unit of energy (joule).

(b) A certain household consumes 650 units of electricity in a month. How much is this electricity in joules ?

Answer 1

(a)
1 Kwh = 1000 W x 3600s (1 hr)
= 3600000 J
=$3.6\times {10}^{6}J$

(b) 1 unit = 1 kilowatt hour = 3 600 000 joules

Thus, 650= 650 x 3 600 000 = 2340000000 J = $2.34\times {10}^9$ J