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You have been given with a cup of coffee...

You have been given with a cup of coffee which is too hot to drink .Which among the following is the best method to cool it? Why?
(i) Placing it in a beaker containing water
(2) Placing it on the surface of wood
(3) Placing it on the surface of an iron block

Text Solution

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The best method to cool it, is to place it in water. The heat transfer rate with wood is less compared to the iron block but when it placed on an iron block, only the bottom surface is in contact with the iron block. But when it is placed in a beaker containing water the surface area in contact with water is more. So, the heat transfer rate is also more. Hence, the cooling effect is more when it is placed in water.
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