How Microwave Ovens Work

By: Tomas Bayas and Sebastian Naranjo

Intro

• Microwaves are part of our everyday lives. We use them everyday and most of us don’t pause and think for a moment how they work. We take for granted that we will have a microwave to heat our food up, but hundreds of years ago people didn’t have this technology. This is why we thought it would be important to explain how they work and how physics are part of them.

A Little Bit of History

• The first microwave was invented in 1947 by Percy Spencer.

• He came up with the idea while he was working on building radar sets in WWII.

• The first microwave was rather big to the ones we have right now. It had a height of 1.8 meters and weighted up to 750 lbs.

Electromagnetic Waves

• An electromagnetic wave have both electric and magnetic fields that simultaneously oscillate at a ninety degree angle with each other.

• This waves produce energy in the form of radiation and they can be classified into two separate types, ionizing and non-ionizing.

• Ionizing radiation has the ability to change molecules and damage tissue that is exposed to it; this is what happens with atomic bombs.

• Non-ionizing doesn’t have that amount of energy so it isn't harmful and microwaves produce this type of radiation.

• Different electromagnetic waves have different intensities.

• This is determined by the frequency of the waves which is the number of waves in a given unit of time. The greater the frequency, the greater the intensity.

• From the frequency we can determine the wavelength as well using the formula v=λf. You would need the velocity as well to use this formula.

• From frequency we can also get the period of the wave, which is the time it takes for one full wave to cycle.

• The formula for period is f=1/T where f stands for frequency and T stands for period.

Structure

• The magnetron is an important component of microwaves, it produces the electromagnetic waves which allows food to be cooked.

• Once the electromagnetic waves are produced they go inside the cooking chamber.

• The magnetron has an anode and a cathode an in the space between them, refereed as the anode cylinder, the magnetic energy is created which transfers into the waves.

How They Operate

• When turn on the microwave oven energy starts to be provided to the system through the socket which goes through the magnetron which creates the electromagnetic waves.

• The waves then travel to the oven cavity where the food is and begin to heat it up.

• There are three types of energy conduction, convention, and radiation.

• Radiation is the transfer of waves to heat up something. The waves are bouncing off the metal walls of the oven and are absorbed by the food which then starts to heat up.

• The air inside the oven doesn’t heat up due to the fact that air has less molecules so therefore it produces less friction than a solid object like the food.

• Due to the friction of the molecules microwaves work better on more solid objects.

Our Motivation

• We decided to do this topic because there are a number of things that we use in our everyday life that go unnoticed into how vital they are for us and we don't appreciate them. Microwaves are an example that we use everyday but don't value how different life would be if we didn't have them. In the past people needed to go through a long tedious process to heat up their food and in the present we just have to turn the microwave on. It is always amazing to see how physics is in objects like those and how physics is present in our everyday life. Most of the time we can look at a microwave and think that it isn't that hard to come up with the idea of it. But the moment it was created, as well as many other important inventions, people invented something that wasn't obvious to everyone and changed the world because of it.

Bibliography • "Microwave Ovens." Microwave Ovens. N.p., June 2009. Web. 20

Apr. 2014. <http://hyperphysics.phy-astr.gsu.edu/hbase/waves/mwoven.html>.

• Zerner, Tobey. "The Physics of Microwave Ovens." The Physics of Microwave Ovens. N.p., Apr. 2010. Web. 20 Apr. 2014. <http://tobyzerner.com/microwaves/>.

• Gibbs, Keith. "Microwave Ovens." Schoolphysics ::Welcome::. N.p., 2013. Web. 20 Apr. 2014. <http://www.schoolphysics.co.uk/age14-16/Wave%2520properties/text/Microwave_ovens/index.html>.