MICROWAVE OVENS Physics 001, Section 001 John Hopkins By: Vasavi Pandey

THE START OF THE MICROWAVE OVEN 1945; the high power microwave was discovered by accident by American engineer Percy Spencer  Spencer was working on an active radar when he discovered the chocolate in his pocket had melted because of microwaves  After that, the first food to deliberately be cooked by a microwave oven was popcorn; second was an egg  Spencer, at the time, worked for Raytheon, a major American "defense contractor"  The company filed for patency in October of 1945 for Spencer's microwave process and an oven that heated food using microwave energy Spencer confirmed all his findings by creating a high density electromagnetic field "by feeding microwave power from a magnetron into a metal box from which it had no way to escape"  When placing food into the metal box, its temperature rose quickly

HOW IT WORKS Microwaves use the behavior of water molecules when subjected to electromagnetic waves In simple terms, microwaves are electromagnetic waves with wavelengths in the range of 1mm - 1m  Microwaves used for cooking are electromagnetic waves processing frequencies around the 2.45 GHz range Electromagnetic waves are waves made up of altering electric and magnetic fields  When a positively charged electron is exposed to an electric field, it experiences a force pointing in the direction of the field  When a negatively charged electron is exposed to the same field, it experiences a forced pointing in the opposite direction of the field Since an electromagnetic wave (like a microwave) is made up of alternating electric fields, a charge exposed to it will experience forces in changing directions

HOW IT WORKS (CONT.) For water molecules, which are dipoles, the net effect would force the molecules into rotation  Since the fields are alternating, the rotation will change from clockwise to counter-clockwise at regular time intervals The water molecules then possess heat energy that rub off of nearby molecules --thus heating the entire body uniformly  Electromagnetic waves in the microwave range are most suitable for this because the water molecules readily rotate when exposed to such frequencies.  This goes on and heats up the food inside the microwave

VARIOUS USES FOR THE MICROWAVE OVEN 1.Dry up herbs 2.Roast garlic 3.Make popcorn 4.Soften sugar 5.Steralize garden soil 6.Dye fabric 7.Decrystalize Honey 8.Create a giant crayon

THE MICROWAVE AND PHYSICS 001 The microwave oven uses microwaves, a form of a wave  Researching the microwave oven goes further into learning about waves and understanding how they work  This relates also to what type of wave an electromagnetic wave is in relation to other waves WHAT I LEARNED It was really interesting to learn about the microwave oven because I never really understood how the device worked A microwave is an every day device that no one really puts much thought into; we just use it and take it for granted  It was nice to understand what goes into making a microwave oven I learned how electromagnetic waves and water molecules are both used together to get a microwave working. Before researching the device, I never would have put the two together. I also learned how the device heats up food items. I also got even a stronger understanding of waves

BIBLIOGRAPHY 1."Electromagnetic Waves." Drexel. Drexel, 12 May Web. 20 Apr VILLANUEVA, JOHN C. "How Do Microwaves Work." Universe Today. N.p., 18 Nov Web. 19 Apr