On a day when I am in hurry to go to office, I have a fixed quantity of rice which was just cooked and kept in a bowl. In order to cool it quickly, which one of the following is the best option?
A.Let it be kept on the table in a room where there is no fan, no air conditioner
B.Let it be kept in a room with AC set at a temperature around 23 °C and a ceiling fan (or table fan) operating at slow speed
C.Let it be kept in a bowl of water (at room temperature) and operating a ceiling fan (or table fan) at full speed✓ Correct
D.Let it be kept in a bowl of water at room temperature only
Explanation
Cooling depends on the rate of heat transfer. Water has a much higher thermal conductivity and specific heat capacity than air, so keeping the rice bowl in water dramatically increases conductive heat loss compared to air. Additionally, running a fan at full speed enhances convective cooling by evaporating the surface water and carrying heat away faster (forced convection). Combining conduction through water with forced convection from the fan provides the fastest cooling. Option (d) only uses water without forced convection, so it is slower than (c).
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