Thermodynamics HW Solutions 864

Thermodynamics HW Solutions 864 - Chapter 11 Fundamentals...

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Chapter 11 Fundamentals of Thermal Radiation 11-9C Microwaves in the range of 10 are very suitable for use in cooking as they are reflected by metals, transmitted by glass and plastics and absorbed by food (especially water) molecules. Thus the electric energy converted to radiation in a microwave oven eventually becomes part of the internal energy of the food with no conduction and convection thermal resistances involved. In conventional cooking, on the other hand, conduction and convection thermal resistances slow down the heat transfer, and thus the heating process. 2 to 10 m 5 μ 11-10 Electricity is generated and transmitted in power lines at a frequency of 60 Hz. The wavelength of the electromagnetic waves is to be determined. Analysis The wavelength of the electromagnetic waves is λ= = × c v 2 998 10 60 8 . m / s Hz(1/ s) 4.997 10 m 6 Power lines 11-11 A microwave oven operates at a frequency of 2.8
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