Physics

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.

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Given,

Power of the electric heater = 3kW

Time for which the electric heater is used = 10 hours

We know,

Energy consumed = power × time

(i) Energy consumed in kWh

$\text{Energy} = 3 \times 10 \\[0.5em] \Rightarrow \text{Energy} = 30 kWh \\[0.5em]$

(ii) Energy consumed in joule.

$1 kWh = 3.6 \times 10^6 J \\[0.5em] 30 kWh = 30 \times 3.6 \times 10^6 \\[0.5em] \Rightarrow 30 kWh = 1.08 \times 10^8 J \\[0.5em]$

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