how long will a1.2kw electric kettle take to heat 0.9kg of water from 20 degree celisus to 100 degree celisus
heat = 0.9 kg * (100ºC - 20ºC) * 4.186 J/g⋅ºC
calculate the heat needed (in Joules)
a Watt is a Joule per second ... 1.2 kW is 1.2 kJ per second
divide the Joules needed by the Watts available to get the seconds (time)