A 4.74 kW kettle holds 1kg of water at a room temperature of 21 °C. How long would it take the kettle to bring all the water to a boiling point of 100 °C? Assume the kettle is 100% efficient and the specific heat capacity of water is 4200 j/kg.
Q = mc(T2-T1) = 14200(100-21) =331800.p = Q/tt = Q/pt = 331800/4740 ( not forgetting to convert from kW to W)t=70 seconds
