An electric kettle (rated accurately at 2.5kw) is used to heat 3 kg of water from 15°C to boiling point. It takes 9.5 minutes. Then the amount of heat that has been lost is

Energy consumed in 9.5 min is given by=(2⋅5×1000)×(9⋅5×60)=14⋅25×105 joule Energy consumed in heating=3×1000×(100−15) joule =2⋅55×105 joule Loss =(14⋅25−2⋅55)105≈10⋅70×105 joule