Water of volume 2L in a container is heated with a coil of 1kW at 27oC. The lid of the container is open and energy dissipates at rate of 160 J/s. In how much time temperature will rise from 27oC to 77oC?[Given specific heat of water is 4.2kJ/kg]
A
8 min 20 s
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B
6 min 2 s
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C
7 min
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D
14 min
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Solution
The correct option is B 8 min 20 s
QNET=QSUPPLIED−QREJECTED=1000−160=840J
Density=MassVolume
Mass=2KG
We also know that Q=m×S×(ΔT)and Q=E×t
So, time taken will be:
t=m×S×(ΔT)E
t=2×4200×50840=500second
Or we can say 1minute=60second
So in 500second=8.33minute=8minuteand0.333×60second=8minuteand20second