Physics-
General
Easy
Question
The only possibility of heat flow in a thermos flask is through its cork which is 75 cm2 in area and 5 cm thick. Its thermal conductivity is 0.0075 cal/cm secoC. The outside temperature is 40oC and latent heat of ice is 80 cal g–1. Time taken by 500 g of ice at 0oC in the flask to melt into water at 0oC is
- 2.47 hr
- 4.27 hr
- 7.42 hr
- 4.72 hr
The correct answer is: 2.47 hr
Þ 
Þ t = 8.9 ´ 103 sec = 2.47 hr
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