We all know that stainless steel utensils, or metal objects in general, including cutlery, should never be placed inside a microwave oven while operational. Today’s everyday explained explores the reason behind the warning.
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How does a microwave oven work?
To understand why we should not be putting metal inside a microwave oven, we first need to know how the appliance works. Microwaves are a form of electromagnetic radiation, like radio waves, but with shorter wavelengths and higher frequencies.
According to Caroline A. Ross, a professor in the department of Materials Science and Engineering at the Massachusetts Institute of Technology (MIT), a microwave oven generates microwaves by a device called a magnetron, and they are made to pulse back and forth inside the appliance at a carefully calibrated frequency.
Microwaves bounce off the oven’s interior metal walls, can pass through paper, glass, and plastic, but they get absorbed by food. More specifically, the microwaves get absorbed by the food’s water content. The transfer of energy that takes place leads to the water molecules of food oscillating back and forth rapidly, which creates heat and warms up the food. It can also cook the food from the inside out, the outside in, or uniformly, depending on where the water lies.
Why we should not put stainless steel or metal inside a microwave
{{/usCountry}}Microwaves bounce off the oven’s interior metal walls, can pass through paper, glass, and plastic, but they get absorbed by food. More specifically, the microwaves get absorbed by the food’s water content. The transfer of energy that takes place leads to the water molecules of food oscillating back and forth rapidly, which creates heat and warms up the food. It can also cook the food from the inside out, the outside in, or uniformly, depending on where the water lies.
Why we should not put stainless steel or metal inside a microwave
{{/usCountry}}In the words of Professor Ross, it is “counterproductive to put something metallic inside your microwave oven if you want to heat it up.” She explained that a metal object placed inside the microwave oven deflects the microwaves away from the food.
The deflected electromagnetic waves jump around erratically inside the appliance, which can end up damaging the interior of the oven. In fact, metal is so good at reflecting microwave radiation that the window built into the front of microwave ovens contains a fine metallic mesh that we can see through, but from which microwaves cannot escape.
In some situations, metal placed inside a microwave can become very hot. The oscillation of the microwaves can also produce a concentrated electric field at the corners or the edge of a metallic object, and thereby ionise the surrounding air. When the electric fields are strong enough, they can cause arcing, or the formation of visible sparks. This can damage the internal components of the appliance and become a larger safety hazard in general.