Monday, June 01, 2015

Why does food in a microwave oven rotate ?

The microwave oven was invented after a serendipitous incident when Percy Spencer accidentally melted chocolate in his pocket.

Percy Spencer worked at Ratheon, developing radar transmitters during World War II. These radar transmitters sent out microwave signals from a magnetron tube for detecting objects. One day in 1945, he accidentally discovered that the candy in his pocket was getting heated up and melting while standing next to the powered on magnetron.

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Working on this principle, he went on to invent the first working microwave oven in 1947. he called it Radarange.The first thing he cooked in it was popcorn.

But why does the microwave have a rotating glass bowl ?

It is quite entertaining to watch the rotating food in a microwave, but this rotation serves a purpose. The magnetron in a microwave oven can send the at the food, but it does not go uniformly all around. There are hot spots and cold spots within the microwave. To ensure that the food is evenly heated, it has to move around to expose all parts of the food to the microwaves equally.

Is it dangerous to open the microwave door while it is still on ?

The microwave's magnetron is supposed to switch off when you open the door. But that is just a failsafe safety mechanism. It is always better to press the stop button on the microwave BEFORE the door open button. If you have a faulty microwave, then you will be exposed to microwave radiation(though all microwave ovens in use now have safety mechanisms).

So, although it is not recommendable, it is not a real danger to open it any time. You may open the microwave door whenever you please,. Microwaves takes less than a tenth of a second to die down, and the moment you open the door a kill switch is activated for the magnetron.

Another interesting trivia is that Australian radio astronomers where confused for quite a while by strange microwave radiations picked up by their super-sensitive radio telescopes. They couldn't figure out if they were from space or interference. They called them Perytons. Later they discovered that they were caused by some old microwave ovens being opened by the door open switch before the timer was done.

A video explaining how microwave ovens work by the Engineer guy.

What to do if my Microwave stops spinning ?

  1. Unplug the microwave. Safety first, kids.

  2. Remove the glass tray and the circular turntable guide. Wash them both in warm, soapy water to get rid of anything stuck. Pay special attention to the rollers on your turntable guide, making sure they're able to spin freely.

  3. Clean the internal cavity. Make sure to check your microwave's center cavity to make sure it's free of movement-hindering (and gross) leftover food.

  4. Check that the drive bushing is working. Make sure that the drive bushing, the plastic mechanism in the bottom of the microwave's interior that the glass tray turns on, isn't worn out or split in two. If it is, you'll need to have it replaced.

  5. Put it back together. Put the turntable guide back into the circular groove. Place the glass tray turntable over the turntable guide and onto the drive bushing. Adjust until the drive bushing should fits perfectly into the grooves of the glass tray.

  6. Test it out. Zap a mug of water for a short bit to see if you fixed the problem. Do not run the microwave without anything in it.

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