Question

An electric iron of power 1.5 kW is used for 30 minute.to press the clothes Calculate the electrical energy consumed in (a) kilowatt hour (b) joule.

Answer 1

P = $\frac{w}{t}$
∴ Eelectrical energy $W=P\times t$
P = 1.5 kW, t = 30 minute = $\frac{1}{2}$ hr
= $1.5\times \frac{1}{2}$
= 0.75 kWh

(b) 1 kWh = $3.6\times {10}^6$ J
∴ 75 kWh = $0.75\times 3.6\times {10}^6$
= $2.700\times {10}^6$
= $2.7\times {10}^6$ J