A certain microwave oven produces microwaves of frequency 2450 MHz with a power

Question

A certain microwave oven produces microwaves of frequency 2450 MHz with a power of 502 W. How long should it take to heat 840 g of water, initially at room temperature, to the boiling point? Assume that all the microwave energy is absorbed by the water. (The microwave frequency is significant because the water molecule has a rotational resonant frequency at 2450 MHz. This means that water very effectively absorbs radiant energy at this frequency, thereby raising its rotational kinetic energy and its temperature. The specific heat of water is 4186 J/kg–C°, and assume that the room temperature is 20°C.)

Explanation / Answer

Heat required, Q = m Cwater deltaT

Q = 0.840 x 4186 x (100 - 20) = 281299.2 J

Power = Q/t

t = 281299.2 / 502 = 560.3 sec

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