Determine what voltage the electric boiler is designed for, which heats 0.2 kg of water from 14

Determine what voltage the electric boiler is designed for, which heats 0.2 kg of water from 14 ° C to boiling in 5 minutes, provided that a current of 2A flows through its winding.

Data: t (operating time of the electric boiler) = 5 min (300 s); m (mass of heated water) = 0.2 kg; t0 (initial water temperature) = 14 ºС; I (current in the winding of the electric boiler) = 2 A.

Constants: С (specific heat capacity of water) = 4200 J / (kg * ºС); t (boiling point) = 100 ºС.

1) Heat for heating water: Q = C * m * (t – t0) = 4200 * 0.2 * (100 – 14) = 72240 J.

2) The voltage for which the boiler is designed: Q = U * I * t, whence U = Q / (I * t) = 72240 / (2 * 300) = 120.4 V.