The microwave oven, a tool that we use often in our busy lives to heat up foods when we just don't have the time or patience for a conventional oven to do its work.
How does this device work?
It's pretty simple if we use the basics of physics to explain it. Vibrations from the high frequency radio waves cause the water and fat cells in food to generate heat through friction of the molecules.
An example of this using a turkey shows the molecules positive
and negative particles acting through these vibrations to cause friction.
J. Carlton Gallawa -- http://www.gallawa.com/microtech/howcook.html
"In microwave cooking, the radio waves penetrate the food and excite water and fat molecules pretty much evenly throughout the food. There is no "heat having to migrate toward the interior by conduction". There is heat everywhere all at once because the molecules are all excited together. There are limits of course. Radio waves penetrate unevenly in thick pieces of food (they don't make it all the way to the middle), and there are also "hot spots" caused by wave interference, but you get the idea. The whole heating process is different because you are "exciting atoms" rather than "conducting heat"." -- Howstuffworks.com
From Wikipedia.org:
"Microwaves, also known as Super High Frequency (SHF) signals, have wavelengths approximately in the range of 30 cm (1 GHz) to 1 mm (300 GHz)."
and
"A microwave oven uses a magnetron microwave generator to produce microwaves at a frequency of approximately 2.4 GHz for the purpose of cooking food. Microwaves cook food by causing molecules of water and other compounds to vibrate. The vibration creates heat which warms the food. Since organic matter is made up primarily of water, food is easily cooked by this method."
From http://www.gallawa.com/microtech/howcook.html:
"Microwaves possess three basic characteristics:
* Just as sunlight shines through a window, microwaves pass right through some materials. Materials such as glass, paper, and plastic are transparent to and generally unaffected by microwaves.
* Microwaves are reflected by metal surfaces, much as a ball would bounce off a wall. The metal walls of the cooking space actually form a cavity resonator. In other words, the enclosure is designed to resonate the microwaves as they are radiated from the magnetron tube. The principle of resonance may be illustrated using sound waves. When a piano key is struck, it produces sound vibrations or sound waves. Sometimes a note is played on a piano, and an object across the room, perhaps a wineglass, can be heard vibrating and producing the same sound.
Metamaterials are manmade objects that are composed of two or more specifically arranged and distinct materials (Rowe.). They can be 3d printed in sheets, applied directly to a surface, or even be produced using a special method to silk. These metamaterials have the power to manipulate electromagnetic radiation including sound waves, light waves, and ocean waves. Most all materials have a refractive index which dictates how waves would pass through or bounce off of them. For example, a pencil placed in a glass of water will look bent due to the natural refractive index of the water. However, if the water had a negative refractive index then the pencil would appear to bend back onto itself. Metamaterials allow objects to maintain a negative refractive index which bends the waves in ways other materials cannot.
good emitter of heat radiation so a lot of heat will be lost to the
In 1894 Percy Spencer was born. He said when he was little he “liked to tinker and discover how things worked”. When he was 16 he went to help his family with a job at a machine shop. That job taught him how to work with electricity, so when he got older he became an electrician an Raytheon. Raytheon was the company that invented smaller radios and they had families all over America, that adopted these radios, so it was very popular. One of the later experiments that Raytheon conducted was the magnetron which made microwaves (tiny waves) to create heat. One day, Percy Spencer came near the magnetron while it was switched on, when he came near the machine he had a bar of chocolate he was carrying which melted and gave him an idea. No one knew the potential of the magnetron until the chocolate melted. (Passage
are known to emit low levels of radiofrequency energy in the microwave range when in
Conduction, convection and radiation are the three methods through which heat can be transferred from one place to another. The (www.hyperphysics.com) first method is the conduction through which heat can be transferred from one object to another object. This process is defined as the heat is transmitted from one to another by the interaction of the atoms and the molecules. The atoms and the molecules of the body are physically attached to each other and one part of the body is at higher temperature to the other part or the body, the heat begins to transfer. A simple experiment through which conduction can be understood easily is as follows. First of all, take a metallic rod of any length. Hold the rod in the hand or at any stand made up of the insulator so that the heat does not transfer to the stand. Heat up the one end of the rod with the help of the spirit lamp. After sometime, touch the other end of the end, the other end of the becomes heated too and the temperature of the other end of the rod has also increased. Although only one end of the rod is heated with the spirit lamp, but the other end of the rod has also been heated. This is represents that the heat has been transferred from one end of the rod to the other end of the rod without heating it from the other end. So, the transformation of the heat is taking place. This process is called the conduction. Conduction is a process which is lead by the free electrons. As the conduction happens occurs only in the metallic materials, the reason for it is that the metals has the free electrons and they can move freely from one part of the body to another part of the body. These electrons are not bounded by the nucleus so, they can move easily. And when the temperature of the ...
The higher the energy level in an energy source, the lower the wavelength of the energy produced, and the higher the frequency. Differences in wave energy characteristics are used to classify electromagnetic energy.
In these commentaries, Schwarcz also answers questions that people and the media have and offer advice to people. For example, a listener asked “How long one should allow microwaved food to stand after cooking to ‘allow the microwaves to escape?” He responded by describing how the food on the inside is cooked through the heat transfer from the exterior, which allows the food to finish cooking. Additionally, it is essential to leave the food to stand for a few minutes. However, this does not allow the microwaves heat to leave, but for the interior to finish cooking as well as the exterior. If you don’t leave the food to settle there for a few minutes than it will leave the cooking process incomplete.
Conduction, Convection, and Radiation Heat transfer is the way heat moves through matter to change the temperature of other objects. There are three types of heat transfers, Conduction, Convection, and Radiation. The first kind of heat transfer, conduction, is heat transferring through direct contact of materials. This would be the same thing as a pan on the stove. The heat from the stove touches the pan directly, therefore making the pan hot.
As discussed in class, submission of your solutions to this exam will indicate that you have not communicated with others concerning this exam. You may use reference texts and other information at your disposal. Do all problems separately on clean white standard 8.5” X 11” photocopier paper (no notebook paper or scratch paper). Write on only one side of the paper (I don’t do double sided). Staple the entire solution set in the upper left hand corner (no binders or clips). Don’t turn in pages where you have scratched out or erased excessively, re-write the pages cleanly and neatly. All problems are equally weighted. Assume we are working with “normal” pressures and temperatures with ideal gases unless noted otherwise. Make sure you list all assumptions that you use (symmetry, isotropy, binomial expansion, etc.).
In conclusion, cooking has evolved as technology has developed. But in the grand scheme of things we still have the same methods. Cooking helped the advancement of the human brain and the advancement of human teeth and our digestive tracts. Today we have restaurants, grocery stores, microwaves, and ovens. And all we started off with was a fire and a piece of meat with a stick stuck through it. Cooking was, is, and will be a vital part of the human life.
Heat energy is transferred through three ways- conduction, convection and radiation. All three are able to transfer heat from one place to another based off of different principles however, are all three are connected by the physics of heat. Let’s start with heat- what exactly is heat? We can understand heat by knowing that “heat is a thermal energy that flows from the warmer areas to the cooler areas, and the thermal energy is the total of all kinetic energies within a given system.” (Soffar, 2015) Now, we can explore the means to which heat is transferred and how each of them occurs. Heat is transferred through conduction at the molecular level and in simple terms, the transfers occurs through physical contact. In conduction, “the substance
All university students know the convenience and importance of the microwave. The microwave is particularly important for students living in the Towers, as this is their only kitchen appliance. Since microwaves are a staple for university students, they become dirty quickly. The best way to keep microwaves clean is to clean up spills immediately. If you can 't, however, do this, follow the steps below. Your microwave will be spotless again almost instantly.
The microwave is a prime example of technology making us happy. If we were to get rid of the microwave, many people would be angry because it is a very helpful and time saving device. If there was no microwave people would not be able to defrost the ground meat they forgot to leave out, nor would they be able to cook a hot pocket for lunch when they were short on time. Some people believe that items that are efficient make society happy.
gigahertz. (1 kilohertz = 1000 hertz : 1 megahertz = 106 hertz, 1 gigahertz =