In an electric kettle, the resistance of a heating element of which is 50 Ohm, 1.2 kg of water

In an electric kettle, the resistance of a heating element of which is 50 Ohm, 1.2 kg of water was poured and heated from 20 C to boiling for 5 minutes. The current consumed by the heating element, 6 A. What is the KDP of the kettle?

The efficiency will be equal to the ratio of the useful amount of heat (used to heat water from 20 degrees to 100 – the boiling point of water) to the amount of heat released by the heating element when current passes through it. Those. Efficiency = Qpol. / Qzatr. = Сm (Tkip-Tinit.) / RtI ^ 2 (c – specific heat capacity of water = 4200, m – mass of water, I ^ 2 – current strength squared, t – time of kettle heating by current, I – current strength). All units of measurement are expressed in SI (5 min. = 300 s). Efficiency = 4200 x 1.2 x (100 – 20) / 6 ^ 2 x 300 x 50 = 0.74666 Ie. about 0.75.