Transcript How Microwave Ovens Work

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.phyastr.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/age1416/Wave%2520properties/text/Microwave_ovens/index.ht
ml>.