Question

(i) If you put a glass of water in a microwave and bring it to boiling temperature, is the energy supplied as heat or work? Explain briefly in 1-2 sentences (ii) Estimate how long it would take in a typical 900-watt microwave to boil a cup of water Assume any reasonable initial temperature for the water

Answer 1

Microwave radiation hits the water molecules present in food, which excites them and causes 'em to vibrate rapidly in situ resulting in the heating up of food.

let us say 1 cup of water that is 0.2 L is boiled or raised in temperature by 80 degree centrigrade then heat required is

= (0.2 x 1000 x 80 x 1 ) cal = 16000 calories = 66944 Joules

time taken by microwave = 66944/900 = 74.38 sec = 1 min 15 sec

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