How much time is needed to heat 1 kg of water from 20 C to 100 C in an electronic kettle with a power of 500 W, if its efficiency is 75%

Data: m (mass of water in the kettle) = 1 kg; t0 (initial temperature) = 20 ºС; t (required temperature) = 100 ºС; Nh (kettle power) = 500 W; η (efficiency) = 75% = 0.75; Cw (specific heat capacity) = 4200 J / (kg * ºС).

Heating duration: t = Qw / (Nh * η) = Sv * m * (t – t0) / (Nh * η) = 4200 * 1 * (100 – 20) / (500 * 0.75) = 933.3 s = 15.56 min.

Answer: It takes 15.56 minutes of time.