Question

In practice the unit kWh is used for the measurement of electrical energy, rather than joule.

Answer 1

Electrical energy = Electrical power × time. For practical applications, devices consuming high electrical power are used over a period of time. This leads to heavy expenditure of electrical energy. To measure such value of energy unit joule is significantly small. Hence, unit kWh is used in practice. Unit 1 kWh represents power of 1 kW used for 1 hour and equals 3.6 × 10⁶ J.