Define power. State the difference between $1$ watt and $1$ watt hour. Establish the relationship between unit of electric energy and $SI$ unit of energy. An electric heater rated $1000\, W / 220 \,V$ operates $2$ hours daily. Calculate the cost of energy to operate for $30$ days at the rate of ₹ $5.00$ per $k W h$

Power is defined as the rate at which electric energy is dissipated or consumed in an electric current.

$1$ watt is the power consumed by a device that carries a current of $1\, A$ when operated at a potential difference of $1\, V$ while $1$ watt hour is the energy consumed when $1$ watt of power is used for $1$ hour.

Commercial unit of electric energy is $k W h$.

$1 kW h =1000 watt \times 3600 s$

$1 kW h =3.6 \times 10^{6}$ watt second

$=3.6 \times 10^{6} J$

Total energy consumed by heater

$=1000 W \times 2 h \times 30$

$=60000 Wh$

$=60 kWh$

Therefore, cost of energy to operate for $30$ days

$=$₹ $5 \times 60=$₹ $300$