A cup of water at 
(system) is placed in a microwave oven and the oven is turned on for one minute during which the water begins to boil. Which of the following option is true ?
Text Solution
Verified by ExpertsD
For water heating in a microwave:
Heat 
: The microwave radiates electromagnetic energy that is absorbed by water molecules, so 
Work (w): As water heats and boils, it expands against atmospheric pressure. The system does work on the surroundings, so 
Internal Energy ( 
): From the first law, 
. Since heat absorbed ( +ve ) is much larger in magnitude than work done against atmosphere (-ve), the net change is 
(confirmed by temperature increase from 
to boiling)
Therefore: 
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