June 30, The easiest way to figure out if a plastic container is safe for the microwave is to look for the Microwave Safe symbol. This stamp of approval, which includes three wavy lines to symbolize radiation, basically says that the container can withstand the heat of the microwave without melting or releasing harmful amounts of chemicals.
Play media Simulation of the electric field inside a microwave oven for the first 8 ns of operation A microwave oven heats food by passing microwave radiation through it.
Microwaves are a form of non-ionizing electromagnetic radiation with a frequency higher than ordinary radio waves but lower than infrared light. Microwave ovens use frequencies in one of the ISM industrial, scientific, medical bandswhich are reserved for this use, so they do not interfere with other vital radio services.
Consumer ovens usually use 2. Many molecules such as those of water are electric dipoles, meaning that they have a partial positive charge at one end and a partial negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field of the microwaves.
Rotating molecules hit other molecules and put them into motion, thus dispersing energy. As noted microwave ovens can operate at many frequencies. Dielectric heating of liquid water is also temperature-dependent: However, due to the lower specific heat capacity of fats and oils and their higher vaporization temperature, they often attain much higher temperatures inside microwave ovens.
Foods high in water content and with little oil rarely exceed the boiling temperature of water. Microwave heating can cause localized thermal runaways in some materials with low thermal conductivity which also have dielectric constants that increase with temperature. An example is glass, which can exhibit thermal runaway in a microwave to the point of melting if preheated.
Additionally, microwaves can melt certain types of rocks, producing small quantities of molten rock. Some ceramics can also be melted, and may even become clear upon cooling. Thermal runaway is more typical of electrically conductive liquids such as salty water.
This idea arises from heating behavior seen if an absorbent layer of water lies beneath a less absorbent drier layer at the surface of a food; in this case, the deposition of heat energy inside a food can exceed that on its surface. This can also occur if the inner layer has a lower heat capacity than the outer layer causing it to reach a higher temperature, or even if the inner layer is more thermally conductive than the outer layer making it feel hotter despite having a lower temperature.
In most cases, however, with uniformly structured or reasonably homogenous food item, microwaves are absorbed in the outer layers of the item at a similar level to that of the inner layers.
Penetration depth of microwaves is dependent on food composition and the frequency, with lower microwave frequencies longer wavelengths penetrating further.
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May This section possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. May Learn how and when to remove this template message A microwave oven converts a large portion of its electrical input into microwave energy.
The other W are dissipated as heat, mostly in the magnetron tube. Such wasted heat, along with heat from the product being microwaved, is exhausted as warm air through cooling vents.
A magnetron with section removed magnet is not shown A microwave oven consists of: One variant of the GE Spacemaker had two taps on the transformer primary, for high and low power modes.
Usually choice of power level doesn't affect intensity of the microwave radiation; instead, the magnetron is cycled on and off every few seconds, thus altering the large scale duty cycle.
Newer models use inverter power supplies that use pulse-width modulation to provide effectively continuous heating at reduced power settings, so that foods are heated more evenly at a given power level and can be heated more quickly without being damaged by uneven heating.
The first is that they should be in one of the industrial, scientific, and medical ISM frequency bands set aside for unlicensed purposes.
For household purposes, 2.Rated 1 out of 5 by Davvi from Worthless Oven 2/24/ I purchased a new home and the Microwave and Oven came with my chefs kitchen. The oven cannot hold a steady temperature it will be the third time having the oven repaired once they changed the temperature controls didn't work, next changed the thermostat, same problem, now the want to change the main control.
Tortilla warmer that keeps tortillas fresh and warm for over 1 hour. Today I found out the microwave oven was invented by accident by a man who was orphaned and never finished grammar school. The man was Percy Spencer.
At the age of just 18 months old, Spencer’s father died and his mother soon left him to his aunt and uncle.
His uncle then died when Spencer was. Westinghouse Counter Top Microwave Oven - WCMB / WCMW Cubic Feet / Watts Just the Right Size, Just the Right Features. This countertop microwave oven delivers watts of power and the quality that the Westinghouse name is known for.
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