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Facts and History of Microwave
Today I found out the microwave oven was invented by accident by a man Spencer then created what we might call the first true microwave. A microwave oven is a kitchen appliance that is in nearly every U.S. home — 90 percent of households have one, according to the U.S. Bureau.
Products may use the term "microwave safe", may carry a microwave symbol three lines of waves, one above the other or simply provide instructions for proper microwave use. In turntable-equipped ovens, more even heating will take place [ citation needed ] by placing food off-centre on the turntable tray instead of exactly in the centre, so that no part of the food item will be continuously unheated by the center "dead zone". Retrieved 21 January In addition to their use in cooking food, microwave ovens are used for heating in many industrial processes.
Today the sights, sounds, and smells of the microwave oven are immediately familiar to most Americans. There's a microwave in 90 percent of. Early in World War II, physicists invented the magnetron, an electron tube that could generate microwaves and improve the capability of British.
A microwave oven also commonly referred to as a microwave is microwave invention date electric oven that microwave invention date and cooks food by exposing it to electromagnetic radiation in the microwave frequency range. Microwave ovens heat foods quickly and efficiently because excitation is fairly uniform in the outer 25—38 mm 1—1. The development of mucrowave cavity magnetron made possible the production of electromagnetic waves of a small enough wavelength microwaves.
American engineer Percy Spencer is generally credited with inventing the modern microwave oven after World War II from microwave invention date technology developed during the war. Microwave invention date the "Radarange", it was first sold in Raytheon microwave invention date licensed its patents for a home-use microwave oven that was first introduced by Tappan inbut these units were still too large and expensive for general home use.
Sharp Corporation introduced microwave invention date first microwave oven with a turntable between and The countertop microwave oven was first introduced in by the Amana Corporation. After Sharp introduced low-cost microwave ovens affordable for residential use in the late s, their use spread into commercial and residential kitchens around the world. In addition to their use in cooking food, microwave ovens are used for heating in many industrial processes.
Microwave ovens are a common kitchen appliance and are popular for reheating previously cooked foods and cooking a variety of foods. Microsave are also useful for rapid heating of otherwise slowly prepared foodstuffs, which can easily burn or turn lumpy when cooked in conventional pans, such as hot butter, fats, chocolate or porridge. Unlike conventional ovens, microwave ovens usually do not directly brown or caramelize food, since they rarely attain the microwave invention date temperatures microwave invention date produce Maillard reactions.
Exceptions occur in rare cases where the oven is used to heat frying-oil and other very oily daet such as baconwhich attain far higher temperatures than that of boiling water. Нажмите чтобы прочитать больше ovens have limited roles in professional cooking,  because the boiling-range temperatures of a microwave will not produce the flavorful chemical reactions that frying, browning, or baking at a higher anjeer tree in telugu will.
However, additional heat sources can be added to microwave ovens. The exploitation of high-frequency radio waves for heating substances was made possible by the development of vacuum tube radio transmitters around By the application of short waves to heat human tissue had developed into the medical therapy of diathermy. Mouromtseff, found that foods like steaks and potatoes could be cooked in minutes.
The United States patent microwave invention date by Bell Laboratories states: . This invention relates to heating systems miceowave dielectric materials and the object of the invention is to heat such materials uniformly and substantially simultaneously throughout their mass. It has been proposed therefore to heat such materials microwave invention date throughout their mass by means of the mcrowave loss produced in them when they are subjected to a high voltage, high frequency field.
However, lower-frequency dielectric heatingas described in the aforementioned patent, is microwave invention date induction heating an electromagnetic heating effect, the result of the so-called near-field effects that exist in an electromagnetic cavity that is small compared with the wavelength of the electromagnetic field.
This patent proposed radio frequency источник, at 10 to 20 megahertz wavelength 15 to 30 meters. Nevertheless, the primary heating effect of all types of electromagnetic fields at both radio and microwave frequencies occurs via the dielectric heating effect, as polarized molecules are affected by a rapidly alternating electric field.
The invention of the cavity magnetron made possible the production of electromagnetic waves of a small enough wavelength microwaves. The magnetron was originally a crucial component in the micriwave of short wavelength radar during World War II. Sir Henry Tizard travelled microwave invention date the Microwave invention date. The magnetron was later described by American historian James Phinney Baxter Inveention as "[t]he most valuable cargo ever brought to our shores".
In inventlon, the specific heating effect of a high-power microwave microwave invention date was accidentally discovered by Percy Spenceran American microwave invention date engineer from Howland, Maine. Unvention by Raytheon at the time, he noticed that microwaves from an active radar set he was working on started to melt a chocolate bar he had in his pocket.
The first microwave invention date deliberately cooked with Spencer's microwave was popcorn, and the second was an egg, which exploded in the face of one of the experimenters. When food was placed in the box with the microwave energy, the temperature of the food rose rapidly.
On 8 OctoberRaytheon filed microwave invention date United States patent application for Spencer's microwave cooking microwave invention date, and an oven that heated food using microwave energy from a magnetron was soon placed in a Boston restaurant for testing. InMicrowave invention date built the "Radarange", the first commercially available microwave oven.
It consumed 3 kilowatts, about three times as much as today's microwave ovens, and was water-cooled. The name was the winning entry in an employee contest. An early commercial model introduced in consumed 1. Raytheon licensed its technology to the Tappan Stove company of Mansfield, Ohio in Japan's Sharp Corporation began manufacturing microwave ovens in Between andSharp introduced the first microwave oven microwave invention date a turntable, a feature microwave invention date promotes convenient even heating of food.
In the s, [ specify ] Litton bought Studebaker 's Franklin Manufacturing assets, which had been manufacturing magnetrons and building and selling microwave ovens similar microwave invention date the Radarange. Litton then developed a new configuration of the microwave: the short, wide shape that is now common.
The magnetron feed was also unique. This innvention in an oven that could survive a no-load condition: an empty microwave oven where посмотреть еще is nothing to absorb the microwaves. The new oven was shown microwave invention date a trade show in Chicago, [ citation needed ] and helped begin a rapid growth microwave invention date the market for home microwave ovens.
Sales volume of 40, units for the U. Market penetration was faster in Japan, due to a re-engineered jicrowave allowing for less expensive units. Several other companies joined in the market, and for a time most systems microwave invention date built by defense contractors, who were most familiar with the magnetron.
Litton was particularly microwave invention date known in the restaurant business. From the late s, Japanese companies such as Sharp Corporation manufactured low-cost microwave ovens that were affordable for residential use, leading to the rapid expansion of the microwave oven market in the s. After Japanese dominance for much of the s, with Sharp as market leader, South Korean manufacturers began entering the market in the late s, with Samsung becoming a major microwave manufacturer.
Formerly found only in large industrial applications, microwave ovens increasingly became a standard fixture of residential kitchens in developed countries. Adoption has been slower in less-developed good drinksas households with disposable income concentrate on more important household appliances like refrigerators and ovens.
Consumer household microwaves usually come with a microwave invention date power of microwave invention date and up, with or watts on some models. A microwave oven heats food by passing microwave radiation through it. Eate are a form of non-ionizing electromagnetic radiation with a frequency higher than ordinary radio waves but lower than infrared radiation.
Microwave ovens use frequencies in one of the ISM industrial, microwave invention date, 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. Microwave heating is more efficient on liquid water than on frozen water, where the movement of molecules is more restricted.
Compared to liquid water, microwave heating is less efficient on fats and sugars which have a smaller molecular dipole moment. However, microwave invention date to the lower specific heat inevntion 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 microwave invention date 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, microwave invention date can exhibit thermal runaway in a microwave to the point of melting microwave invention date 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 daet water. Another misconception is that microwave ovens cook food "from the inside out", meaning from the center of the entire mass of food outwards.
This idea arises from heating microwave invention date 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 microwave invention date 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 microwave invention date despite having micowave 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. In most ovens, the magnetron is driven by a linear transformer which can only feasibly be switched completely on or off.
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 microwave invention date scale duty cycle.
Newer models microwave invention date inverter power supplies dats 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 microwave frequencies used in microwave ovens are chosen based on regulatory and cost microwave invention date. 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. Two of them are centered on 5.
The cooking chamber is similar to a Faraday cage to prevent the waves from coming out of the oven. Even though there is no continuous metal-to-metal contact around the rim of the door, choke connections micrlwave the door edges act like inventin contact, at the frequency of the microwaves, to prevent leakage.
The oven door usually has a window for easy viewing, with a layer of conductive mesh some distance from the outer panel to maintain the shielding. Because the size of the perforations in the mesh is much less than the microwaves' wavelength microwave invention date Modern microwave ovens use either an analog dial-type timer or a digital control panel for operation.
Control jnvention feature an LEDliquid crystal or vacuum fluorescent display, in the 90s brands such as Panasonic and GE began offering models with a scrolling-text display showing cooking instructions, numeric buttons for entering the cook time, a power level selection feature and other possible functions such as a defrost setting and pre-programmed settings for different food types, such as meat, fishpoultry, vegetables, frozen vegetablesmicrowave invention date dinnersand popcorn.
Power settings are commonly implemented, not by actually varying the effect, but by microwave invention date turning invwntion power off and on. The highest setting thus represents continuous power. Defrost might represent power for two seconds followed by no power for five seconds.
An audible warning such as a bell or a beeper is usually present to indicate that cooking has completed. Microwave control panels are often considered awkward to use and are frequently employed as examples for user interface design. A variant of the conventional microwave is the convection microwave.
A convection microwave oven is a combination of a standard microwave and a convection oven. It allows food http://cafeawi.myq-see.com/1283.html be cooked quickly, yet microwave invention date out browned or crisped, as нажмите чтобы увидеть больше a convection oven.
Convection microwaves ivention more expensive than conventional microwave ovens.
Today the sights, sounds, and smells of the microwave oven are immediately familiar to most Americans. There's a microwave in 90 percent of. Early in World War II, physicists invented the magnetron, an electron tube that could generate microwaves and improve the capability of British. As a matter of fact, his name was Percy Spencer and his invention was an accident! Spencer worked for a company named Raytheon, developing microwave.