Question

29. An electric immersion heater raises the
temperature of 3 kg of water from 30°C to 70°C
in 7 minutes. Find the power of the heater. Take
specific heat capacity of water = 4200 J kg ' °C.
bi bila
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Answer 1

An immersion heater can increase the temperature of 2kg water 60°C in 100 minutes. How long does it take to melt a block of 0.5kg ice at 0°C? Given that specific latent heat of fusion of ice is 334; and the specific heat capacity of water is 4200

Considering the system to be isolated from the surrounding.

Energy required to raise the temperature of water by 60 degrees is 2*4200*60=504KJ.

Power of heater=energy per unit time=504000/(100*60)=84W

Energy required to melt ice=0.5*334=167KJ

Time taken=167000/84= seconds.1988.09 s or 33.135 minutes