Question

An engineer is doing an energy audit on a kitchen. She needs to work out how much electrical energy a 0.355kg stainless steel electric kettle needs to heat 0.850 L of water from 15 degrees Celsius to its boiling point. Calculate the energy needed, assuming that the kettle converts all the electrical energy to thermal energy and that it loses no heat in its surrounding.

Answer 1

The engineer needs to work out the energy needed to raise the temperature of 0.355 kg of steel and 0.85 litres of water from 15 celsius to 100 celsius, which is a temperature rise of 85 celsius.The specific heat capacity of water is 4, 200 J/kg/kelvin (kelvins similar to celsius, here).The specific heat capacity of steel is not given in the question posted.The total energy would be 0.344 x SHC of steel x 85 + 0.85 [litres of water converted into kg of water] x 4, 200 x 85.That energy is supplied by electrical energy in Joules.