Define kwh. Establish the relationship
between 1 kWh and SI unit of energy (joule)?

Commercial unit of electrical energy is kWh.
1 kWh is the amount of electric energy consumed by 1000 W
electric appliance when operates for 1 hour.
\(1kwh=1000w*3600sec\)
\(1kwh=1000joule per sec*3600sec\)
\(1kwh=3.6*10^6 joule\).