An electric kettle rated 2.1 kilowatt contains 1 kg of water.Assuming no heat loss and neglecting the thermal capacities of kettle,how long will it take to start to boil the water if its initial temp is 20C?

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Answer 1 · 2017-12-23T05:34:32

Given the power rating of the electrical kettle #P=2.1kW#

If time taken to raise the temperature of 1 kg of water from #20^@ to 100^@C# is t sec, then the electrical energy required for this will be

#=Pt=2.1t" "kJ#

Again the heat energy reqired to raise the temperature of 1 kg of water from #20^@ to 100^@C# is

#1xx4200xx(100-20)J=336KJ#

So #2.1t=336#

#=>t=336/2.1=160s=# 2 min 40 sec