A water heater of power 2000 W is used to heat water. The specific heat capacity of water is 4200 J kg - 1 K - 1 . The efficiency of heater is 70 % . Time required to heat 2 kg of water from 10 ° C to

Question

A water heater of power 2000 W is used to heat water. The specific heat capacity of water is 4200 J kg - 1 K - 1 . The efficiency of heater is 70 % . Time required to heat 2 kg of water from 10 ° C to 60 ° C is _____ s . (Assume that the specific heat capacity of water remains constant over the temperature range of the water).

TestHub · Accepted Answer

Heat provided to water will be responsible for increase in temperature. Therefore, we can write

$η \times P \times t = M \times s \times Δ T$

Now, $η = \frac{70}{100} = 0.7$ and $energy = power \times time$ .

Therefore,

$t = \frac{2 \times 4200 \times (60 ° - 10 °)}{0.7 \times 2000} s = 300 s$

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