Microwave Oven

A microwave oven is an oven that cooks or heats food by microwave radiation, usually at a frecuency of 2450 MHz through the food. (a wavelenght of 12.2cm).

Food’s water, fet and sugar absorb energy from the microwave beam in a process called dielectric heating. The molecules get affected through this process and they start moving. This molecular movement generates heat.

Microwave ovens have:

Humidity Sensor

Digital Clock

Rotating Turntable

Control Keypad

Microwave oven consists of:

Magnetron, a high-powered vacuum tube that generates coherent microwaves.

Magnetron control circuit

Waveguide, is a physical structure that guides the propagation of electromagnetic waves

Cooking chamber

The cooking chamber is a Faraday cage enclosure to prevent the microwaves escaping into the surroundings. The higher the oven power, the quicker food cooks. With a high wattage in a small space it is possible to get greater power.

A microwave oven uses microwaves to heat food. Microwaves are radio waves.

Microwave ovens, the commonly used radio wave frequency is 2,500 megahertz (2.5 gigahertz). Radio waves in this frequency range have an interesting property: they are absorbed by water, fats and sugars. When radio waves are absorbed they are converted directly into atomic motion -heat.

Mircrowaves have another interesting property: they are not absorbed by most plastics, glass or ceramics. Metal reflects microwaves, which is why metal pans do not work well in a microwave oven.

In microwave cooking no heat has to migrate toward the interior by conduction. There is heat everywhere all at once because the molecules are all excited together.

In a microwave oven, the air in the oven is at room temperture, so there is no way to form a crust.

In 1946 the microwave oven was was discovered by Percy Spencer . He was working on an active radar set when for the Raytheon company when he noticed a strange sensation, and saw that a. peanut bar he had in his hand started to melt. After that he placed some popocorn kernels near the tube and popcorn started popping all over the laboratory. Dr. Spencer fashioned a metal box with an opening into which he fed microwave power. The energy entering the box was unable to escape, thereby creating a higher density electromagnetic field.

In 1946 Raytheon patented the microwave cooking process and in 1947 the first commercial microwave oven hit the market, the Radarange. It was almost 6 feet (1.8 m) tall and weighed 750 pounds (340 kg) and used to cost around $2,500.

In 1965 Raytheon acquired Amana, which introduced the first popular home model, the countertop Radarange in 1967 at a price point of $495. It was a 100-volt microwave oven, which cost just under $500 and was smaller, safer and more reliable than previous models.

By the seventies, more and more people were finding the benefits of microwave.

By 1975, sales of microwave ovens would, for the first time, exceed that of gas ranges. The following year, a reported 17% of all homes in Japan were doing their cooking by microwaves, compared with 4% of the homes in the United States the same year. Before long, though, microwave ovens were adorning the kitchens in over nine million homes, or about 14%, of all the homes in the United States. In 1976, the microwave oven became a more commonly owned kitchen appliance than the dishwasher, reaching nearly 60%, or about 52 million U.S. households.

Microwaves come in three general sizes and power levels:

Small
Interior space: .7 to .8 cubic feet
Counter space: 11Height by 20Width by 14Deep inches
Power level: 600 to 700 watts


Medium
Interior space: 1.4 to 1.6 cubic feet
Counter space size: 13 by 21 by 16 inches
Power level: 900 by 1,100 watts

Large
Interior space: 1.8 to 2.1 cubic feet
Counter space: 14 by 24 by 18 inches
Power level: 1,000 by 1,150 watts

There are three general oven types:

Single-purpose oven - The bulk of microwaves fall into this category--the oven operates solely as a microwave and comes in the sizes listed above. Plan to spend about $70 to $90 on a small oven, around $130 to $150 on a medium oven, and between $160 and $220 on a large oven.

Microwave/convection oven - A microwave/convention combo cooks, browns, or crisps food in addition to microwaving and may operate as a microwave or convection oven alone, or cook in both methods at once. Generally a little bigger than a large microwave, they're priced at around $400.

Over-the-range oven - If you lack counter space, consider an over-the-range model, which replaces the stove's range hood and provides venting capability for the range, as well as the microwave. Generally available in medium to large sizes, this type costs about $420 to $450.

Full-sized microwave oven - The Panasonic NN-T965SF is one of the few models with inverter technology, a method that delivers continuous cooking power (rather than the on/off cycling typical of most microwaves), resulting in more evenly heated food from edge to middle. This model comes in stainless steel to match today's more stylish appliances. Reviews say this model's performance matches its sleek design, with a roomy 2.2-cubic foot interior. You get a large 16.5-inch turntable, plus all the standard functions including a popcorn button, delay start, keep warm function and auto defrost. If you don't need anything this large or fancy, however, the Kenmore (below) performs nearly as well.

Mid-sized microwave - Reviews advise buying the largest model you can (larger models perform best in general), but if your space and budget are more limited, the mid-sized Kenmore 63252 requires less space without sacrificing cooking ability. This 1200-watt oven has a heating sensor, delay timer, 14-inch turntable and child lock. If you're planning mostly on reheating leftovers and popping popcorn, experts say you really don't need much more than this Kenmore microwave oven.

Convection microwave - Convection technology uses a small fan to circulate hot air through the oven. This helps brown food for crispy French fries and crunchier pizza crust. The top-rated mid-sized Kenmore Elite has a heat sensor, auto defrost, removable rack and turntable as well as dial controls. The Kenmore Elite convection microwave is about the same size as the standard Kenmore 63252 above, so if you don't care about browning foods in your microwave, you can save $90 by skipping the convection feature.

Compact microwave oven - The Sharp R-230 is just barely large enough for a dinner plate, but its small size makes it a good choice for dorm rooms or other tight spots. According to reviews, the Sharp reheats food well and is easy to use. Owners posting comments to Epinions especially like the small microwave. The 800-watt Sharp comes in black or white, includes 15 auto settings, a popcorn button, digital display and an 11-inch turntable.

Over-the-range microwave - The Whirlpool is a top performer if you're looking for a microwave that mounts under the cabinet over your range. This 1000-watt full-sized microwave oven has a capacity of 1.5 cubic feet, and ships with a four-speed exhaust fan to vent your cooking area. Keep in mind, however, that these types of microwaves can cost three times as much as countertop models, and installation and venting can be tricky.

Most microwaves cannot function properly when metal containers and utensils are used; arcing (lightning like flashes) may occur. Metals can be identified by their shiny appearance, or by names like aluminum, stainless steel, cast iron, or copper etched on the utensil, not all plastics and glassware can be used in the microwave.

In order to determine if a glass item is safe for microwaving, read the label on the container; it should specify “microwave safe” or “heat resistant.” Ceramics should be avoided because some may contain small traces of metal which can cause damage to the magnetic tube over an extended period of time. Ceramics are those utensils which are made of clay or pottery. Brand names may include Earthenware or Farberware.

As actual microwaves move in unpredictable patterns, most ovens employ a revolving turntable set in the bottom to turn food as it cooks and a fan to redistribute the waves. Some food, however, will always require stirring and repositioning in order to cook thoroughly.
Microwaves in proper functioning will not operate if the door does not shut completely; if it does, it needs to be serviced immediately to avoid further exposure.

With some microwaves, closed glass jars, whole eggs (even pierced), and bottles with narrow necks should not be used because they may explode during cooking. There are also air vents located on the top or sides of microwave ovens. Make sure these vents are kept open and free of food particles and debris. These vents are necessary to keep the oven’s mechanical parts from overheating.

To reduce the risk of fire in the oven cavity, don’t overcook food. If cooking food does ignite, keep oven door closed, turn off oven (or cancel timing device), and disconnect power cord or shut off the power from fuse box. In the unlikely event these precautions must be exercised, have the oven serviced to evaluate the possibility of further usage.

Osborne/Jenks Productions, Inc. is proud to produce the largest and most popular consumer home shows on the East Coast. This home show series is a dynamic showcase of home products and home services that will help you with all your home building, design and improvement needs.

Additional Links

Kitchen and household appliances
Appliance Parts Depot
Kitchen Appliances and Replacement Parts
Heating Ventilation and Air Conditioning
Kitchen Items