Question

An electric iron of power 1.5 kW is used for 30 minutes to press the clothes. Calculate the electrical energy consumed in

1. kilowatt-hour
2. joule.

Answer 1

(a) Given: P = 1.5 kW; t = 30 minutes = `30/60 = 1/2`hr

∴ P = `w/t`

∴ W = P × t

∴ 1.5 × `1/2`

= 0.75 kwh

(b) 1 kWh = 3.6 × 10⁶ J

∴ 75 kWh = 0.75 × 3.6 × 10⁶

= 2.700 × 10⁶

= 2.7 × 10⁶ J