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Microwave oven

  1. E.M.G. YADAVA WOMEN’S COLLEGE, MADURAI-14 (An Autonomous Institution – Affiliated to Madurai Kamaraj University) Re-accredited (3rd Cycle) with Grade A+ and CGPA 3.51 by NAAC THE PHYSICS OF HOUSEHOLD APPLIANCES MICROWAVE OVEN Mrs.R.Kayalvizhi, Head & Assistant Professor Miss K.Ramya, Assistant Professor Department of Physics E.M.G Yadava Women’s College, Madurai
  2. A Microwave oven is a kitchen appliance that heats and cooks food. Microwave ovens convert electrical energy into a form of electromagnetic radiation called microwaves.
  3. What are microwaves? em spectrum • Microwaves are a form of electromagnetic energy, like light waves or radio waves. 1. • Used in communications such as to relay long-distance telephone signals, television programs and computer information across the earth or to a satellite in space, radars and in detecting speeding cars 2. • Microwave has become most familiar as the energy source for cooking food 3.
  4. Contd... 1. • All microwaves use a timer for the cooking time, at the end of cooking time, the oven switches itself off. • Microwave ovens heat food without getting hot themselves. 2. • A 2006 study found that microwaving wet sponges for two minutes (at 1000 watt power) removed 99% of coliforms, E. coli and MS2 phases. 3. • So, microwaves oven are great to use.
  5. History of Oven • It was Invented accidentally by Dr. Percy Spencer in 1945. • While testing a magnetron during work, he discovered the candy bar in his pocket melted. 1. • Experimented with other food products (popcorn and eggs), and realized microwaves can cook foods quickly. • At 1947, 1st commercial microwave oven produced (called Radarange)- Mostly used by restaurants, railroad cars, ocean liners and military. 2. • Improvement and refinements made by 1967, 1st domestic microwave oven produced. • By 1975 sales of microwave ovens exceeded that of Gas Ranges. 3.
  6. Microwave oven : early days. 1. • The first microwave oven was priced at $2,000.00 to $3,000.00. 2. • Mostly used by restaurants, railroad cars, ocean liners and military. • In 1980, it becomes necessity for every home maker. 3. • In 1976, the microwave oven became a more commonly owned kitchen appliance. Microwave oven by now. 4. • Microwave ovens heat food without getting hot themselves.
  7. Technical Design Basic design of a Microwave oven. • A transformer • a magnetron • a stirrer, a waveguide 1. • A control panel is located on the external casing where oven cavity is normally bolted. 2. • There is a front panel on the oven body by which user can control/program the machine. 3.
  8. Basic design of Microwave Oven
  9. A Magnetron: Here the yellow part in the middle is cathode and the surrounding bronze part is anode. Magnetron •Magnetron is a high-powered vacuum tube which generates microwave. •It’s a diode type electron tube.  •There’s a cathode at the center of a magnetron. A ring shaped anode surrounds the cathode.
  10. Magnetron WAVEGUIDE • A waveguide is a structure that guides microwaves. • Generally waveguide is made of brass, copper, silver, aluminium, or any metal that has low bulk resistivity. STIRRER • Looks like a fan. • Usually situated at the top of the cavity. • Moves the microwaves around the cavity.
  11. Main chassis  This is the place where every parts of a oven is organized  The main chassis is placed on the pallet, and the cavity is screwed on to the chassis.  And the door is attached next to the cavity.  A front panel that allows the operator to select the various settings and features available for cooking is attached to the chassis.
  12. A Schematic diagram of oven
  13. How do microwaves cook food? 1. Inside the strong metal box, there is a microwave generator called a magnetron. When you start cooking, the magnetron takes electricity from the power outlet and converts it into high-powered, 12cm (4.7 inch) radio waves. 2. The magnetron blasts these waves into the food compartment through a channel called a wave guide. 3. The food sits on a turntable, spinning slowly round so the microwaves cook it evenly.
  14. Contd.. 4. The microwaves bounce back and forth off the reflective metal walls of the food compartment, just like light bounces off a mirror. When the microwaves reach the food itself, they don't simply bounce off. Just as radio waves can pass straight through the walls of your house, so microwaves penetrate inside the food. As they travel through it, they make the molecules inside it vibrate more quickly. 5. Vibrating molecules have heat so, the faster the molecules vibrate, the hotter the food becomes. Thus the microwaves pass their energy onto the molecules in the food, rapidly heating it up.
  15. Types of Oven There are three types of microwave ovens: 1. Solo 2. Grill and 3.Convection. Solo microwaves are considered basic or entry level. A solo microwave is a basic/ entry level microwave designed to reheat food and beverages, cook noodles, and defrost frozen foods. Solo microwaves use electromagnetic radiation to cook food and drinks. Solo microwave ovens can be used in both commercial and domestic kitchens. These microwave use watts to convert energy into heat, which then cooks the food. Grill microwaves are considered the next step up: A grill microwave is a microwave that gives families the grill taste without needing to fire up an outdoor grill. A grill microwave oven can do everything a solo microwave can do plus grill pizza, chicken, and fish.
  16. Contd... Convection microwaves are at the top. The main difference between the three are the included features, watts, and price. Convection microwave ovens include all of the cooking options of solo and grill microwaves and have the ability to bake foods. The convection microwave uses a different heater and fan combination to cook all of the foods listed plus more. Solo and grill microwaves use metal boxes to direct watts toward the food to cook. Convection microwaves, on the other hand, pushes heat through the microwave using a fan which creates a better cooking environment.
  17. It saves time and energy. It is safer than general fuel stoves. Taste of the foods remain same. If properly used, microwave cooking does not affect the nutrient content of foods. Reduces the consumption of oil. Advantages of Microwave Oven
  18. Health Hazards  Microwave radiation can heat body tissue the same way it heats food.  Exposure to high levels of microwaves can cause a painful burn.  Microwave oven used low level of microwaves, within the region of non- ionizing radiation.  Microwaving converts vitamin B12 from an active to inactive form.  Still uncertain in the effects of humans from long term exposure to low level of microwaves.
  19. Maintenance of Oven • Step 1: Fill a bowl with 2 cups of water and 4 tablespoons of vinegar. • Step 2: Add a toothpick to prevent boiling over. • Step 3: Microwave the bowl for five minutes. • Step 4: Let the bowl sit for three minutes. • Step 5: Wipe the microwave down with a sponge.
  20. Preventive Maintenance  Use microwaveable containers. Non-microwaveable plastic containers can melt and even leave toxic particles in your food. Make sure you use containers that are specifically labelled as microwave-safe. These are often made of ceramic, glass, or tougher plastic.  Cover your food. Use a microwave-safe plastic cover over your dishes or use the lids on your microwave-safe food containers. Splashes happen during the microwaving process as the liquid heats up, and preventing them from hitting the walls of the microwave makes cleanup easier and protects the paint and metal of the oven.  Never put metal in your microwave. The microwaves emitted from the oven bounce off of metallic materials, so metal in the oven will cause the interior to heat up unevenly and can cause damage. This includes aluminum.  Make sure the door closes properly. If the door is damaged or the seal is cracked, food won’t cook evenly and radiation can escape.
  21. Conclusion  The microwave oven was a very beneficial inventions that has make life easier for people everywhere all over the world.  Even though the microwave was invented a very long time ago it is still used toady and is still being improved by technology.
  22. References 1."Microwave cooking and nutrition". Family Health Guide. Harvard Medical School. 6 February 2019. Archived from the original on 17 July 2011. Retrieved 13 April 2021. 2. Pitchai, K. (2011). 'Electromagnetic and Heat Transfer Modeling of Microwave Heating in Domestic Ovens' (Unpublished master's thesis). University of Nebraska at Lincoln. Retrieved August 28, 2020 3. "Microwave Technology Penetration Depths". Püschner GMBH + CO KG MicrowavePowerSystems. Retrieved 1 June 2018. 4.Health, Center for Devices and Radiological (12 December 2017). "Resources for You (Radiation-Emitting Products) - Microwave Oven Radiation". U.S. Food and Drug Administration. Retrieved 1 June 2018. 5. "Microwave Oven". Encyclopedia Britannica. 26 October 2018. Retrieved 19 January2019. 6. Gallawa, John Carlton (1998). "The History of the Microwave Oven". Archived from the original on 31 May 2013. 7. Datta, A. K.; Rakesh, V. (2013). "Principles of Microwave Combination Heating". Comprehensive Reviews in Food Science and Food Safety. 12 (1): 24– 39. doi:10.1111/j.1541-4337.2012.00211.x. ISSN 1541-4337.
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