Physics

Why does the microwave oven not heat some objects and why should not metal objects be placed in it?


The microwave oven, which is present in most homes, often emits microwaves in the 2.5 gigahertz house. The interesting feature of this frequency range is that radiation considerably excites asymmetric molecules such as water, oils and sugars. Thus, when the appliance is used to heat food, only these molecules increase their internal energy, causing a rise in temperature.

The material of the dishes and pots is mostly made up of molecules of extremely symmetrical structure, so their heating is very small. But when we put a food on a plate to be heated, is it not hot when removed from the microwave oven? The answer is yes, he is. However, microwaves are not the reason for this heating, but the direct contact of the dish with the heated foods.

And why shouldn't we put metal objects in the microwave oven?

For two main reasons: first, because metal surfaces reflect microwaves, causing a kind of shielding that prevents waves from reaching liquid molecules. The other reason is that the electric field inside the furnace causes electric currents to appear in the metals, which eventually charge and heat up quickly. Thus, if there is something like a piece of paper or anything that could ignite inside the microwave, a fire could be caused.