A continuous flow water heater (geyser) has an electrical power rating = 2 kW and efficiency of conversion of electrical power into heat = 80%. If water is flowing through the device at the rate of 100 cc/sec, and the inlet temperature is 10°C, the outlet temperature will be
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Question

A continuous flow water heater (geyser) has an electrical power rating = 2 kW and efficiency of conversion of electrical power into heat = 80%. If water is flowing through the device at the rate of 100 cc/sec, and the inlet temperature is 10°C, the outlet temperature will be

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G1 Physics · Accepted Answer

Apply energy conservation. Sensible heat is Q=mcΔT and phase-change heat is Q=mL. Heat lost by hotter parts equals heat gained by colder parts. Evaluating the given data/statements gives B: 13.8°C. Therefore the correct answer is B.