Question
Name and define the commercial unit of energy. Express it in joules. Where is it used?
Or
Define one kilowatt hour. Express it in joules.
Solution
The commercial unit of electric energy is kilowatt-hour (kWh).
One kilowatt hour is defined as the electric energy consumed by an appliance of power 1000 watt in one hour.
1 kWh = 1 kW x 1 h
= 1000 W x 1 h
= 1000 Js-1 x 3600 s
1 kWh = 3600000 J
= 3.6 x 106 J
The electrical energy used in households, industries and commercial establishments is expressed in kilowatt hour.
Electrical energy used is expressed in terms of ‘units’ in our monthly bills.
Here 1 unit means 1 kilowatt hour.
