In an electric kettle, when heated at 220V and a current of 6a, 4 kg of water from 20 to 80

In an electric kettle, when heated at 220V and a current of 6a, 4 kg of water from 20 to 80 ° C was heated in 20 minutes. Determine the efficiency of this kettle.

These tasks: U (voltage on the kettle in use) = 220 V; I (current) = 6 A; t (duration of the kettle) = 20 minutes (in SI t = 1200 s); m (mass of heated water) = 4 kg; t1 (initial temperature) = 20 ºС; t2 (end temperature) = 80 ºС.

Reference values: Sv (specific heat capacity of water) = 4200 J / (kg * K).

The efficiency of the kettle used is determined by the formula: η = Ap / Az = Sv * m * (t2 – t1) / (U * I * t).

Let’s calculate: η = 4200 * 4 * (80 – 20) / (220 * 6 * 1200) = 0.636 (63.6%).