Microwave oven is one of the most widely used household appliances. Most of homes and most of conveniences store and restaurants have microwave oven. The reason for its popularity is that it cooks food in an amazingly short amount of time. They are also extremely efficient in their use of electricity because a microwave oven heats only the food – nothing else. In this article, we’ll discuss the mystery behind the magic of “meals in a minute” with microwave cooking.
The oven is a box like structure made of metal having a front opening built in which has a door. One side on the door has hinges and the other side includes a latch. Behind the see-through door is a mesh which helps in the representation of the microwaves. The construction of the latch within the device offers a few mini switches with regard to extra security. The unit shut down automatically if ever the door is unlatched. The door will stay close until the appliance will be run. The device cannot be run till the door is closed.
1.Principle
It works on Dielectric heating( Water, fat, and other substances in the food absorb energy from the microwaves).
2.Construction
- The inside of the microwave oven is named cavity. This microwave oven part is constructed of stainlesss steel. After the cable is plugged in and the switch is on, the microwave is able to use. The outside even offers the display and control panel to offer information for what must be accomplished. Right behind this particular control panel is a circuit board that operates this kind of product as well as helps make your instructions appear.
- You will find there’s fan inside which sucks in air flow through vents located in the side as well as across the circuit board as soon as the oven is operational. This air is blown from your cooling fins of the magnetron. It then slides out of those cooling fins and also gets ducted past the light and enters the particular cavity by holes positioned in the cavity. Air allows in picking up moisture from the food preparation procedure taking place and guides it out of the oven through exterior vents in microwave oven.
- You will find temperature receptors that can detect in case something is too very hot and the product will de-activate automatically if perhaps some thing is certainly bad. The control circuit provides power to the higher voltage transformer. Furthermore, it contains a capacitor and also big diode with its secondary section. This particular microwave oven part helps to secure the microwave oven form to be damaged.
- The particular magnetron is one of the essential microwave oven parts and is the source of microwave generation inside the oven. It’s stimulated by using a relay procedure and the microwaves generated are led to the cooking food chamber via a little window.
- THE microwave resistant turn table is positioned on to the floor of the cavity to provide rotation to the foods so your foodstuff is cooked equally. This specific turntable is operated with the help of a little knob like structure, that is linked by a belt to some low rpm motor.
- The elements as well as circuits of a microwave oven are quite dissimilar to those contained in Televisions and other appliances. They present some complicated as well as exclusive difficulties with regard to technicians as well as technicians. They are usually unique and vary from company to brand name. In case there is any breakdown of microwave oven parts, it is best to obtain authentic spares fitted by just qualified personnel to get basic safety and longer life of the device.
Working
A microwave oven uses microwaves to heat food. Microwaves are radio waves. In the case of microwave ovens, the commonly used radio wave frequency is roughly 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 they are absorbed they are converted directly into atomic motion and motion is converted into heat. Microwaves in this frequency range have another interesting property: they are not absorbed by most plastics, glass or ceramics. And metal reflects microwaves, which is why metals cause spark in a microwave oven. The reason that metal reflects microwaves is that no electronic waves resident in inside of conductor because conductor’s conductivity is infinity as we studied in our course. The property in this paragraph is possible because the frequency 2,500 megahertz is resonance frequency of water.
Let’s look at this in detail. Molecules of all food are consist of a dipole and have positive charge in one side and have negative charge in another side. If we put electromagnetic fields in this, all molecules are rearranged : +charge is to negative
pole and –charge is to positive pole. In this process molecules heat is produced by friction. The frequency of microwave oven is 2,500 megahertz as we saw before. Then microwave of this frequency change the direction of electromagnetic fields 2,500,000,000 times in 1 second. Consequently the heat efficiency of a microwave oven is greatly high.
You often hear that microwave ovens cook food “From the inside out.” What does that mean? If you bake a cake in a conventional oven, normally you would bake a cake at 350degrees F or so, but let’s say you accidentally set the oven at 600 degrees instead of 350. What is doing to happen is that the outside of the cake will burn before the inside even gets warm. In a conventional oven, the heat has to migrate (by conduction) from the outside of the food toward the middle. You also have dry, hot air on the outside of the food evaporating moisture. So the outside can be crispy and brown while the inside is moist.
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 that “conducting heat”.
In a microwave oven, the air in the oven is at room temperature, so there is no way to form a crust. That is because it heats up foods by ‘microwaves’ instead of ‘heat conduction’.
ADVANTAGES AND DISADVANTAGES
ATTENTIONS IN USING MICROWAVE OVEN
1. If the container is metal spark is generated and no foods heat up.
2. If food is different in ingredients heating velocity could be different. For instance the food contained more fat will be heat up fastly.
3. Bad influence to human body of microwave in microwave oven is nearly only the thermal effect. And safe level of microwave is 10mW/cm2. Leakage of microwave is mostly occurred in the gap of oven and door. Therefore it is important to pay attentions that gap length is not differed.
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