How a Microwave Works

How a Microwave Works
By Zach Betten

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What is a Microwave? A microwave oven or microwave is a kitchen appliance that cooks or heats food by using electromagnetic waves. This happens by using microwave radiation to heat materials such as water and other things within the food. This leads to food being more evenly heated throughout. Basic microwave ovens heat food quickly and efficiently. One setback is that they do not brown or bake food in the way conventional ovens do. This makes cooking certain foods impossible to do in this type of oven. Microwaves heat foods containing water, sugars, and fats. They do not heat glass, paper, or plastic food containers. So microwaves are very energy efficient; they don't waste energy heating everything in the oven. Inputs
1) Electromagnetic waves. One input that helps make microwaves work are electromagnetic waves to cook food. Electromagnetic waves are energy waves that travel at the speed of light. Microwaves are a type of electromagnetic wave that is non-ionizing. That means that they affect molecules by heating them up, not by changing the structure of their molecules. When the waves enter the microwave, the heating up starts. So that means the input here would be the electromagnetic waves. 2) Control Sections
Microwave ovens have two main sections, the control section and the high voltage section. The control section includes a timer, a system to control power output, and safety systems known as interlocks. The high voltage section includes parts that step up the power from the usual household amount of one hundred fifteen volts to a tremendously high three thousand volts! These volts are what starts the heating up that we are so used too. 3) Electricity
The process of microwaving food starts when electricity is introduced into the microwave oven through its electric plug. The electricity moves on through interlock switches. These switches are designed to cut off the power whenever the door is opened and whenever the microwave oven overheats. Other circuits attach to the timer and control the length of the cooking cycle. Processes Microwave ovens use many combinations of electrical circuits and mechanical devices to produce an output of microwave energy for heating and cooking. The systems of a microwave oven can be divided into two sections, the control section and the high voltage section. 2) Control Section The control section consists of a timer, a system to control the power output, and interlock and protection devices. The components in the high voltage section serve to step up the house voltage to high voltage. The high voltage is then converted microwave energy. Basically, here is how it works. Electricity from the wall outlet travels through the power cord and enters the microwave oven through a series of fuses and safety protection circuits. These circuits include fuses and thermal protectors that are designed to deactivate the oven in the event of an electrical short or if an overheating condition occurs. If something like this were to happen the microwave runs the risk of breaking or even catching on fire. If all systems are normal, the electricity passes through to the interlock and timer circuits. It then travels to the magnetron where they are converted to microwaves and then those microwaves are spread around in the microwave by the blowing fan. When then oven door is closed, an electrical path is also established through a series of safety interlock switches Setting the oven timer and starting a cook operation extends this voltage path to the control circuits.

Generally, the control system includes either an electromechanical relay or an electronic switch. Sensing that everything is ready to go, the control circuit generates a signal that causes the relay to activate. Then it produces a voltage path to the high voltage transformer. By adjusting the on-off ratio of this activation signal, the control system can govern the application of voltage to the high-voltage transformer. So it can control the on-off ratio of the magnetron tube and therefore the power of the microwave. Some models use a fast-acting power control relay in the high-voltage circuit to control the output power.
2) High Voltage Section
In the high voltage section, the high-voltage transformer serves to increases the typical household voltage, of about 115 volts, to the high amount of approximately 3000 volts! This powerful voltage could be even deadly for humans. But it is just what the magnetron tube needs to do its job, to convert the high voltage in to waves of electromagnetic cooking energy. The microwave energy is transmitted into a metal channel called a waveguide, which feeds the energy into the cooking area where it comes into contact with the slowly revolving metal blades of the stirrer blade. What these blades do is shoot out the microwave energy throughout all places in which it might hit food. Some waves go directly toward the food and hit it, while others come into contact with the walls and flooring. But thanks to a special metal screen, microwaves also reflect off the door. So, the microwave energy reaches all surfaces of the food from every direction. All microwave energy remains inside the cooking cavity. When the door is opened, or the timer reaches zero, the microwave energy stops, just as turning off a light switch stops the glow of the lamp.
Output
1) Food The output of this system would be the food all warmed up and ready to eat. The food enters the microwave frozen, cold, or uncooked and leaves it steamy, warm and ready to eat.
2) Electricity As the electricity is transformed into microwaves they are able to be evenly distributed in the machine to evenly warm up your food. The electricity is what makes this whole thing work, and with out it this output or even machine wouldn’t work at all.
Feedback
There is a lot of valuable information that a microwave provides us with. For example, it shows us how electricity can be used to make food, and how many different components for a machine can be used together to make things work and our lives easier. This machine could very well be the basis for many other inventions we are yet to see.

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"How a Microwave Oven Works." ZYRA / Zyra's Website Www.zyra.org.uk. Web. 19 Apr. 2010. ;.