Which of the following phenomena is most important when foodstuff is cooked in a microwave oven?
Which of the following phenomena is most important when foodstuff is cooked in a microwave oven? Correct Answer Dielectric heating
A microwave oven is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range.
This induces polar molecules in the food to rotate and produce thermal energy in a process known as dielectric heating.
So that microwave heating is a sub-category of dielectric heating at frequencies above 100 MHz.
Microwave ovens heat foods quickly and efficiently because excitation is fairly uniform in the outer 25–38 mm (1–1.5 inches) of homogeneous, high water content food items.
Important Points
Dielectric heating working:
The material to be heated is placed inside the coil. The heat in the material to be heated is produced by eddy currents.
Power loss due to eddy currents is eddy current loss and appears in the form of heat.
[ alt="F1 Jai 27.3.21 Pallavi D8" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jai_27.3.21_Pallavi_D8.png" style="width: 309px; height: 172px;">
The eddy current loss is
We ∝ Bmax2 f2 / ρ
Bmax = Maximum flux density
f = Supply frequency
ρ = Resistivity of the metal piece
Since the eddy current loss is proportional to the product of the square of supply frequency and square of flux density, therefore by controlling the flux density and supply frequency the amount of heat can be controlled.
