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Question
An electric heater of power 3 kW is used for 10 h. How much energy does it consume? Express your answer in
- kWh,
- joule.
Solution
(i) Energy consumed = power × time
Energy = 3 kW × 10 h = 30 kWh
(ii) 1 kilowatt hour (kWh) = 3.6 × 106 J
30 kWh = 30 × 3.6 ×106 J
= 108 × 106 J
= `108/100 xx 100 xx 10^6` J
= 1.08 × 106 J
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