How much water can be heated from 18 ° C to boiling in 10 minutes in an electric kettle, if the voltage in the network

| April 12, 2021 | education

How much water can be heated from 18 ° C to boiling in 10 minutes in an electric kettle, if the voltage in the network is 220 V, and the current is 4 A. The efficiency of the kettle is 80%. The specific heat capacity of water is 4.2 kJ / kg * K.

Data: t0 (initial water temperature) = 18 ºС; t (duration of the electric kettle) = 10 minutes (600 s); U (voltage) = 220 V; I (current) = 4 A; η (kettle efficiency) = 80% (0.8).

Reference data: t (boiling point of water) = 100 ºС; according to condition C (specific heat of water) = 4.2 kJ / (kg * K) (4200 J / (kg * K)).

We express the mass of water from the equality: η * U * I * t = C * m * (t – t0), whence m = η * U * I * t / (C * (t – t0)).

Calculation: m = 0.8 * 220 * 4 * 600 / (4200 * (100 – 18)) ≈ 1.23 kg.



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