Question

400g of water at temperature 15°c is placed in an electric kettle.The power rating of kettle is at 3.0kw.calculate the energy required to raise the temperature to 100°c?

Answer 1

142,3 KJ

Explanation:

the net heat required is:
`Q= m xx Cp xx Delta T= 0,4 kg xx 4.186 (KJ)/(Kg°C) xx (100-15)°C= 142,3 KJ`
to calculate the energy required is necessary to know the heat missing during the heating or the efficiency of the Kettle. Since it isn't told i suppose 100%, so the energy will be 142,3 KJ
The power of the kettle is an unnecessary data. It can be usefull to know the necessary time:
3 kW = 3 kJ/s
`t= E/P = (142.3 kJ)/(3(KJ)/s)= 47,5 s`