While heat energy can make molecules vibrate, there is another way to achieve the same result — taking advantage of electrical charges. Like a magnet, they each have a positive charge at one end and a negative at the other.
This means they can be jostled around with a magnetic field. In a microwave oven, this is achieved by generating and passing short radio waves, known as microwaves, within the unit.
The device that converts electrical energy to microwaves — called the magnetron — sends microwaves into the oven cavity, where they bounce off the reflective inner surface. Microwaves, like other waves on the electromagnetic spectrum, are wave-shaped patterns of electricity and magnetism that move together at the speed of light. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital.
Chad Mueller, assistant professor of chemistry at Birmingham-Southern College in Alabama, replies: "A microwave oven cooks food because the water molecules inside it absorb the microwave radiation and thereby heat up and heat the surrounding food.
Get smart. Sign Up. When we input microwave radiation into the potato, the potato acts as a resonance cavity, trapping some of the electromagnetic field inside.
The rest of the power is reflected back through the port. As can be seen in the simulation below, the resonance cavity creates a strong peak in the center of the potato where the dissipated power is at its highest. Dissipated microwave power distribution within the potato. This microwave field induces heating inside of the potato. After five seconds have passed, we can look at the amount of heat that has been generated within the potato.
In the simulation, we can observe that only the center of the potato has begun to heat after five seconds. This leads to the hot center and cold exterior that we sometimes experience when heating food in a microwave. If we were to continue heating the potato for a longer period of time, the central temperature in the potato would eventually reach the boiling point, and steam would form and diffuse outwards, accelerating the heat transport and lowering the power dissipation in the center as it dries out.
However, when superheated enough, one or several microexplosions will occur, opening up steam channels to outer parts of the potato. Anyone who has tried microwaving something like mashed potatoes or thick soup has probably experienced these microexplosions, and witnessed their aftereffects on the inside of the microwave oven.
While the simulation discussed above does not include these nonlinear effects, it can serve as a good starting point for a more complex simulation that may include these and other effects. The same mechanisms that cause uneven heating in the potato are also at play in the entire oven.
The shape of the resonating electric field is a pattern of high and low electric field intensity spots inside the oven. The recipient of the e-mail is urged to forward the warning "to friends and family. While this particular e-mail may well be such a hoax, and is probably overly alarmist, the potential problem it warns about is real. The possible "Urban Legend" nature of the specific story that circulates on the Internet is discussed on these Websites: www.
The U. Food and Drug Administration has a page with safety information about microwave ovens: FDA microwave oven page This page updated December 3,
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