How does convection in a microwave work?

Answer 1

A microwave oven takes advantage of the ability of microwave energy to act on atoms at a molecular level. Take a metal box with a door on it, put in some control electronics, a magnetron (the microwave generating device) and a high voltage power source and you're in business.

The user puts an item or items into the cavity (that volume of space where the cooking occurs), and then punches up time and power (often by using preset selections). The high voltage power source powers up the magnetron, and this vacuum tube (a cavity oscillator with its integral magnets) generates microwave energy at about 2.45 GHz. The electromagnetic energy is coupled out of the magnetron, through a waveguide, and into the cavity.

In the oven's cavity, the electromagnetic energy acts on electrically polarized molecules in the food. It causes these molecules to move in an attempt to align themselves with the incoming radiation. As the electromagnetic radiation passes molecules, they attempt to align themselves with the magnetic field of that radiation. But the molecules must constantly move to align themselves with the passing magnetic field. The high frequency energy imparts high frequency "torque" to the molecules, and they try to "flip around" in the passing magnetic field. Those microwaves have a fair ability to penetrate the food, so the items being cooked get heated more evenly than in conventional cooking.

The energy that the microwaves give molecules is expressed as heat. Water molecules have a relatively high dipole moment, and they react more dramatically to the microwave energy than do the molecules in fats or oils; it is the water molecules in foods that convert the larger part of the microwave energy into thermal energy. The technical term for this kind of thermal stimulation is dielectric heating, but we just use the term "nuc" to describe what we're doing with the oven.

How a Microwave Works

Microwaves are radio waves that are roughly around 2,500 megahertz, or 2 gigahertz.

These radio waves have the intresting property of being absorbed by water, fats, and sugars. This absorption converts them directly into atomic motion, thus producing heat. It is not the movement of the microwaves themselves that produces heat, but rather the movement of the excited particles in the food. These waves are also not absorbed by most plastics, ceramics, or glass, meaning that objects made from these materials are 'microwave safe'. Metal, on the other hand, will reflect microwaves, causing sparks when one wave bounces into another. A microwave oven will also produce sparks if turned on when nothing is inside the microwave, as the waves themselves will bounce off of each other, having nowhere else to go.

The magnetron inside a microwave oven uses magnetic energy to create microwaves. Newer microwaves with inverter technology use circuit boards instead of the old transformer/capacitor style microwaves, which makes the microwave more energy efficient, but the overall function is the same.

Unlike a conventional oven, where the heat has to miagrate through the food, the heat produced by a microwave is able to cook food evenly, as all of the particles in the food are excited simulaneously.

Microwaves do have limits. They may not penerate between thick pieces of food. Since the microwaves are emitted from only one side of the oven, it is recommended that you use a microwave which contains a spinning plate, to ensure that food cooks evenly. Furthermore, the air in the microwave remains room temperature, so there is no way to form a crust. This is why microwaveable items sometimes come with a cardboard sleeve. The foil in the sleeve reacts to the microwaves by becoming very hot, causing exterior heat on top of the pastry, thus forming a crust.

Also, the reason microwaves do not escape out of the little holes in the oven is that microwaves have a wavelength of 12.4 centimeters. Any conducting surface that has holes smaller than that will reflect the microwaves, rather than allowing them to pass through. This allows you to view the items in the microwave while still remaining relatively safe from any potential exposure to radiation.

Despite some myths, there are no known health risks from eating microwaved food. Microwave ovens use non-ionizing radiation, which does not mutate your DNA and is not as dangerous as ionizing radiation, such as that found in X-ray machines. However, exposure to microwaves can still burn tissue by heating up the water, fats, and sugars naturally found in human tissues. The eyes are particularly susceptible. For this reason, the FDA recommends that you do not stand directly against your microwave while it is in operation. You should also regularly check your microwave for damage, which may lead to microwave leakage.

Answer 2

They convert energy (in this case electricity) into microwaves, hence the name of the appliance. They work by passing non-ionizing radiation, usually at a frequency of 2.45 gigahertz (a wavelength of 12.24 centimetres (4.82 in)), through the food (from http://en.wikipedia.org/wiki/Microwave_oven)

Answer 3

They work with a magnatron which puts out microwaves and vibrate water molecules which heat up the food

Answer 4

It kinda depends on what kind pf microwave you have, I usually just press the number amount I want it to be cooked and then I just press start:)

Answer 5

Convection microwave ovens combine the technology of microwave cooking and convection heat cooking. It is possible to brown food or even bake cakes in these types of ovens.