An immersion heater rated 1000 W, 220 V is used to heat 0.01 m3 of water. Assuming that the power is supplied at 220 V and 60% of the power supplied is used to heat the water, how long will it take to increase the temperature of the water from 15°C to 40°C?


Given


The operating voltage V


Power consumed P,


Now the resistance of the immersion heater,





Mass of water m is ,


m =1100× 1000


= 10 Kg



We know specific heat of water, s = 4200 Jkg-1 K-1



Given rise in temperature, θ = 25°C



Heat required to raise the temperature of the given mass of water is given by –







Let t be the time taken to raise the temperature of water.


Given the heat evolve is only 60%.


So,





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