Question

An electric heater of power 3 kW is used for 10 h.How much energy does it consume? Express your answer in (i) kWh, (ii) joule.

Answer 1

Energy consumed = power x time
(i) Energy = 3 kW × 10 h = 30 kWh
(ii) 1 kilowatt hour (kWh) = $3.6\times {10}^6$ J
$30kWh=30\times 3.6\times {10}^{6}J=1.08\times {10}^{8}J$