Question

1. State two practical units of electric energy.
2. Define each unit mentioned in (i).

Answer 1

Two practical units of electric energy are watt hour (Wh) and kilowatt hour (kWh).

• Watt hour is the amount of electric energy consumed when an appliance of power $$1\ \mathrm{W}$$ is used for $$1\ \mathrm{h}$$. Hence, $$1\ \mathrm{Wh} = 3600\ \mathrm{J}$$.
• Kilowatt hour is the amount of electric energy consumed when an appliance of power $$1\ \mathrm{kW}$$ is used for $$1\ \mathrm{h}$$. Hence, $$1\ \mathrm{kWh} = 10^3\ \mathrm{Wh} = 3.6 \times 10^6\ \mathrm{J} = 3.6\ \mathrm{MJ}$$.