Where’s the Physics?
Where’s the Engineering?
This is a module developed and piloted by the 2007-2008 Materials Science and
Engineering team under the National Science Foundation program “Utah’s Engineers: a
Statewide Initiative for Growth”. The module was developed in partnership with physics
teacher Matt Lund of Copper Hills High School and piloted in one of his classes.
The module consists of four segments: microwave oven, bathroom scale, telephone
versus cell phone, and balloon catheter inflation device. The class is divided into four
teams and each is given one of the four devices plus a study guide. The objective is for
each team to dismantle or otherwise examine the parts that comprise the device and try to
figure out how the device works, i.e., to explore the physics and engineering that make
the device a functional product. The following timing is recommended for this project:
• During the first class the teams are given 20-30 minutes to dismantle and examine
the parts and discuss a strategy for gathering further information.
• As a homework assignment, the students search for information on the Internet or
elsewhere to gain an understanding of how the device works and the function of
each part.
• The teams are then given additional class time to compile their information,
discuss the information within the team, and plan how they will communicate the
information to the class.
• During a third portion of a class, each team is given about 5 minutes to present
their explanation of the physics and engineering involved in the device.
The total module can be accomplished in about one hour of class time. The hardware is
available on loan from the U of U; and U of U undergraduate students can be available at
the request of the teacher to mentor the high school students.
The devices selected are just examples of what a physics teacher can use in class. This
same approach can work for a wide variety of devices/products to help the students link
the concepts they are studying to real world applications that are important to them.
The following team prepared the four module segments:
• Phil Badger, Undergraduate U of U
• Ashley Cook, Undergraduate U of U
• Paul Slusser, Undergraduate U of U
• Zak Walker, Undergraduate SLCC
• Ben Perschon, Taylorsville High School
• Topher Spencer, West High School
• Matt Lund, Physics Teacher, Copper Hills
• Professor Richerson, U of U, Program Manager
• Professor Shetty, U of U, Principal Investigator
1
Where’s the Physics,
Where’s the Engineering?
Microwave Oven
Student Study Guide
The objectives of this module are to dismantle a microwave oven, to observe the parts
that make up the oven, and to explore all of the ways that physics and engineering are
linked so that the oven meets its required purpose and also is safe and affordable. Table 1
lists key words that will guide you to an understanding of the physics and engineering.
Table 1 Key Words to Understanding the Physics and Engineering of a Microwave
Oven
Microwaves
Microwave cavity
Safety devices
Electronics
Energy transformation
Shielding
Timer
High voltage
Magnetron
Wavelength
Cooling
Capacitor
Heat transfer
Closure mechanism
Heating mechanism
Coupling
Your Challenge:
By examination of the microwave oven parts, exploring the
meaning of the key words, and searching for relevant
information sources, figure out all of the key physics and
engineering issues that needed to be addressed by engineers to
develop a microwave oven. Then work as a team to present this
information to the class.
The following suggestions and questions might help you in your quest.
2
1. Remove the screws that allow you to take off the outer sheet metal case of the
microwave oven. Be sure to save the screws so that you can reassemble the oven.
2. Can you figure out the key components and their function just by looking?
3. How is mechanical engineering involved in designing a closure for the door and a
safety switch?
4. How is electrical engineering involved?
5. Do the devices in the microwave oven perform their function on 110 volts, or are
there components that increase the voltage? Explain.
6. Do any of the components seem to require cooling?
7. What mechanisms of cooling? Convection? Conduction? Radiant transfer?
8. What are microwaves? How do the frequency and wavelength of microwaves
compare with other electromagnetic waves such as light, x-rays, and radio waves?
9. How are microwaves generated in the microwave oven?
10. Is energy transformed from one form to another?
11. What is a magnetron?
12. How does a magnetron work? Hint: Do an Internet search for “microwave oven how
it works”.
13. How do microwaves interact with different materials?
14. Which materials can be used in a microwave oven and which cannot? Why?
15. What is “coupling”?
16. What is “shielding”?
17. How do microwaves interact with food to achieve heating?
18. In a normal oven the food heats from the outside inwards. How does food in a
microwave oven heat? Why? Which mode of heat transfer seems to be the most
efficient or effective?
19. What roles do ceramics/glass play in a microwave oven?
20. What roles do metals play in a microwave oven?
21. What roles do organic materials such as polymers play in a microwave oven?
22. Are all of these materials necessary for the microwave oven to be a successful and
safe product?
23. Are there any other applications of microwaves?
24. What are you learning in physics that can help you understand microwaves and their
applications?
25. How can you most effectively communicate what you have learned about a
microwave oven to the rest of the class?
26. What methods of communication in the sources you found were most effective in
explaining the operation of a microwave oven? (Written, Diagrams, Schematics,
Cartoons, etc.)
27. Make a schematic or flow diagram describing the energy transformation process from
wall outlet to hot food (or you may present this as a written paragraph).
You might consider doing an Internet search for “microwave oven”, “magnetron”,
“microwaves” or other key words.
For example you might consider:
3
www.gallawa.com/microtech/how_work.html
www.gallawa.com/microtech/magnetron.html
www.physlink.com/Education/askExperts/ae379.cfm
www.howstuffworks.com/microwave.htm
Remember that the idea is for you to gain an understanding of how a microwave oven
works and to explain to the rest of the class. Also remember to give proper credit to the
sources of your information.
4
Where’s the Physics,
Where’s the Engineering?
Bathroom Scale
Student Study Guide
The objectives of this module are to dismantle two bathroom scales (one which is a
spring scale and the other which is a digital scale), to observe differences in the parts that
make up the scales, and to explore all of the ways that physics and engineering are linked
so that each type of scale performs its function. Table 1 lists key words that will guide
you to an understanding of the physics and engineering.
Table 1 Key Words to Understanding the Physics and Engineering of a Bathroom
Scale
Spring
Elastic modulus
Integrated circuit
Circuits
Spring constant
Strain gauge
Power supply
Calibration
Hooke’s law
Digital readout
Force vectors
Piezoelectric
Levers
Microprocessor
Precision
Load cell
Your Challenge:
By examination of the two scales and parts and searching for the
meaning of the key words, figure out all of the key physics and
engineering issues that needed to be addressed by engineers to
develop the two types of scales. Then work as a team to present
this information to the class.
The following suggestions and questions might help you in your quest.
1. Carefully remove the outer cover from each scale and draw a sketch of the position of
each part so that you will be able to reassemble the scales when you are done.
5
2. Can you figure out the key components and their function just by looking?
3. By this initial visual observation, what appear to be the major differences between the
scales?
4. Does either scale require a power input? If so, which one and how is the power
provided?
5. How does this scale detect a load and convert the output from that load into a
measurement of weight?
6. What is a strain gauge and how does it work?
7. What is a load cell and how does it work?
8. From observation of the parts, what is the load measuring device used in the digital
scale?
9. How does the load detected by the digital scale get converted into a digital reading?
10. What if a person leans so that they are applying more force to one side of the scale
than the other? How is the digital scale designed to accommodate for this?
11. Search the Internet to see if you can obtain more information about how a digital
scale works.
12. How is physics involved in design of a digital scale?
13. How are materials involved?
14. Now let’s go back and look at the other scale.
15. Does this scale require a power supply?
16. What physics principles are involved in this scale?
17. What is a spring constant?
18. What is elastic modulus and how is it important in design of the scale and material
selection?
19. Will the scale give an accurate reading if the elastic limit is exceeded and the spring
permanently deforms?
20. The spring in this scale is relatively small and is either completely compressed or
extended by a load well below the weight of most people. How is the scale designed so
that the spring is exposed to only a portion of the weight and does not exceed its elastic
limit? Can you measure the levers and do a force balance to answer this question?
21. Why not just use a much larger spring with a much higher spring constant?
22. How does the load on this scale get translated into a reading that the person can see?
What physics and engineering are involved in this linkage?
23. Which of the two scales would you guess could be designed to be most precise or
accurate?
24. How might you calibrate or “zero” each scale?
25. What type of scale would you want to use in the laboratory for accurate
measurements?
You might consider doing an Internet search for some of the key words. You might also
consider the following web sites.
http://home.howstuffworks.com/inside-scale.htm
http://www.madehow.com/Volume-7/Scale.html
http://ezinearticles.com/?Weighing-Scales-101&id=473176
6
Where’s the Physics,
Where’s the Engineering?
Balloon Catheter Inflation Device
Student Study Guide
The University Medical Center, the College of Medicine and the College of Engineering
have a strong partnership to develop new biomedical innovations. This has led to many
spin-off companies and also has attracted major medical companies to the Salt Lake
Valley like Merit Medical. One of their products is an inflation device used to precisely
inflate balloon catheters during angioplasty and other life-saving procedures.
The objectives of this module are to study a fully assembled inflation device plus all of
the parts that make up the device and to explore all of the ways that physics and
engineering are linked so that the device meets its required purpose and is also affordable
to manufacture. Figure 1 shows the items in this module and Table 1 lists key words that
will guide you to an understanding of the physics and engineering.
Table 1 Key Words to Understanding the Physics and Engineering of the Balloon
Catheter Inflation Device
Balloon catheter
Integrated circuit
Energy
transformation
Extrusion
Angioplasty
Digital readout
Thermoplastic
Stint
Power source
Polymer
Piezoelectric
Piezoresistive
Injection molding
Switching
Sealing
Circuits substrate
7
Figure 1 Merit Medical balloon catheter inflation device and all of the parts that
are required to assemble it. Device and parts provided courtesy of Merit Medical,
South Jordan, Utah.
Your Challenge:
By examination of the device and parts and searching for the
meaning of the key words, figure out all of the key physics and
engineering issues that needed to be addressed for Merit Medical
to develop their balloon catheter inflation device. Then work as a
team to present this information to the class.
The following suggestions and questions might help you in your quest.
8
1. Please do not dismantle the whole device, but see if your team can assemble the loose
parts. As you do, make notes about the function of each part and the key physics and
engineering that went into design of each part.
2. Search the Internet to gain an understanding of the meaning and significance of each
key word and why it is important to the design, fabrication and function of the inflation
device.
3. How can pressure be precisely detected and measured by a solid state device?
4. How can mechanical energy be transformed into electrical energy?
5. How can an electrical output be monitored/analyzed and converted into a digital
readout?
6. What are the methods or options of achieving a digital readout (what is the physics
and materials science involved in a digital readout)?
7. Based on examination of the parts, which digital readout do you think Merit Medical
used for their device?
8. What is used to power the device?
9. What is the physics and materials science behind this miniature power source?
10. Note that the pressure sensor and microelectronics are closely integrated. How do
you think this was fabricated and in what kind of environment?
11. Pressurizing a balloon inside a blood vessel requires precise control of pressure and
volume of air. How is the device engineered to allow great care in the volume of air and
the resulting pressure?
12. What complex fabrication challenges needed to be overcome to achieve this precise
control?
13. How do you think the complex shape of the body of the device was fabricated?
14. What type of materials were used, and what special characteristic of the material
made this mode of fabrication possible?
15. Briefly describe to the class this mode of fabrication and explain why it is precise yet
low cost.
16. What characteristics are required of the tubing?
17. What kind of materials would be suitable for the tubing?
18. What fabrication process would be used to make the tubing?
19. Are there any places where effective seals are required in the device? Explain and
describe the material characteristics that allow a good seal.
20. What engineering is required to attach the device to a catheter?
21. What other observations have you made regarding the physics and engineering as
you have conducted your study?
You might consider doing an Internet search for “piezoresistive” or”piezoresistive
sensors”. In particular you might explore www.maxim-ic.com/appnotes.cfm/an_pk/871
or www.microsystems.metu.edu.tr/piezops/piezops.html.
9
Where’s the Physics,
Where’s the Engineering?
Telephone Versus Cell Phone
Student Study Guide
The objectives of this module are to dismantle a telephone and a cell phone, to observe
differences in the parts that make up these two communication devices, and to explore all
of the ways that physics and engineering are involved. Table 1 lists key words that will
guide you to an understanding of the physics and engineering.
Table 1 Key Words to Understanding the Physics and Engineering of a Telephone
and Cell Phone
Copper cable
Electroluminescence
Wavelength
Signal generation
Fiber optic cable
Digital display
Integrated circuit
Signal processing
Wireless
Piezoelectric
Microprocessor
Amplification
Block filter
Semiconductor
Power source
Electrical circuits
Your Challenge:
By examination of the two phones and parts and searching for the
meaning of the key words, figure out all of the key physics and
engineering issues that needed to be addressed by engineers to
develop these important devices. Then work as a team to present
this information to the class. Show drawings, schematics and
pictures as well as actual parts.
The following suggestions and questions might help you in your quest.
10
1. Using screw drivers, open the outer coverings of the telephone and cell phone. Save
the screws and other parts so you can try to reassemble them later.
2. What items can you see? Can you figure out the key components and their function
just by looking?
3. Are there any major similarities or differences in the telephone and the cell phone?
4. Does either require a power input? What is the power source for each?
5. How does the message reach the telephone?
6. How is this message converted to sound? Open up the earpiece and see what you can
see. Go to the Internet and learn different ways a loud speaker can convert an electrical
input into sound.
7. Which of these options do you think is used in the telephone earpiece?
8. Is this same approach used in the cell phone?
9. How does the message reach the cell phone?
10. How strong is this signal compared to the signal received by a telephone?
11. With all of the cell phones in use at any given time, how does your cell phone detect
the weak signal sent to it?
12. How is this signal converted to useful information such as sound or an image in your
cell phone?
13. How big was the first cell phone, and how have engineers been able to decrease the
size so much and at the same time add so many new capabilities?
14. Where does the keyboard light come from when you turn on your cell phone? Can
you dismantle the cell phone further to explore this source of light?
15. How is a digital image produced? What types of materials are required?
16. What options are there for a digital display?
17. Which is most likely used for a digital cell phone image screen?
18. What physics principles are involved in a telephone and a cell phone?
19. How are the mechanical vibrations (sound waves) from your voice converted into a
signal that can be sent by your telephone or cell phone and received by someone else?
20. What is a “block filter” and how does it work? Can you further dismantle the cell
phone to find a block filter?
21. What range of wavelengths are involved for a cell phone?
22. What advanced electronics are integrated into your cell phone, especially to allow it
to be so small?
23. What is an “integrated circuit” or a “microprocessor”?
24. Is it a critical component of your telephone or cell phone? Explain.
25. What new functions would you like to see designed into future cell phones?
You might consider doing an Internet search for some of the key words. You might also
consider the following web site.
http://connected-earth.com and click on “Fun and Games” and then “Gadgets”.
11