PROJECT
ENERGY
Teaching
and Learning for the 21st Century
Energy
Lessons for Middle School
Dennis
W. Sunal
Cynthia
Sunal
Coralee
S. Smith
William
Dwyer
Holly
Loftin Holloway
Editors
Alabama
Science Teaching and Learning Center
The University
of Alabama
Box
870231
Tuscaloosa,
AL. 35487-0231
On the
web at http://www.bamaed.ua.edu/sciteach/energy
CONTRIBUTORS
Dewayne Davis
Thelma Davis
Carol Johnson Dawson
Johnnie Delaine
Clidean Epps
Jeanelle Bland Hodges
Vicki Jenks
Valesca Lopez
Mary Means
Coralee Smith
Cynthia Sunal
Dennis Sunal
Cheryl Sundberg
Partially funded by Alabama DOE/EPSCoR, the Dwight D. Eisenhower Professional Development program administered by the Alabama Commission on Higher Education, and the University of Alabama.
MIDDLE SCHOOL
Biology
Sunlight and Plants (4-8)
Physical Science
Testing Materials for Electrical Conductivity (4-8)
Conductors, Insulators, and Semiconductors (6-12)
Semiconductors: A 21st Century Social Studies Topic (6-8)
Early Concepts An Oil-Drop Model of a Splitting Atom (4-6)
Modeling Nuclear Fission (4-9)
Indirect Observations (4-8)
Investigating Surface Tension (4-8)
Are Acids and Bases Difficult to Identify? (6-8)
Energy Transformation (3-8)
Heat and Temperature: Is There a Difference? (4-8)
Nuclear Reactions: Studying Peaceful Applications (6-8)
Energy to Melt Ice
(7-9)
Earth Science
Global Warming and The Greenhouse Effect (7-12)
Oil Reserves and Drilling
(4-8)
Orientation of Earth
in Space (4-8)
INTRODUCTION
Project Energy is a consortium of university professors, leading scientists and classroom teachers committed to reform in science education. The project began in 1993 with a group of educators interested in increasing the energy literacy of teachers and students throughout the state of Alabama. Project Energy is funded by the U.S. Department of Energy and the EPSCoR Universities of Alabama.
The goals of Project Energy include (a) developing exemplary instructional strategies for teaching energy literacy, (b) enhancing and extending partnerships among students, teachers, energy researchers, and personnel in education, business, and industry, (c) encouraging teachers' professional growth through the development of energy literacy instructional activities and effective energy instructional resource materials which are supportive of the state science curriculum, (d) disseminating information relating to energy literacy, (e) collegial mentoring to expand the exemplary energy classroom model to other Alabama teachers and students, (f) increasing access and skillful use of technology which facilitate and strengthen communication among teachers and students and (g) monitoring and evaluating energy literacy performance through the use of summative evaluations and portfolio projects.
Since 1993, Project Energy teachers have participated in technology and energy related workshops in Tuscaloosa and Auburn, Alabama and Oak Ridge Tennessee. The workshops provided participants opportunities to increase their energy knowledge base and acquire skills in teaching energy topics using technology. In addition, the participants have presented energy literacy workshops at the Annual Alabama Science Teachers Association Conference in Birmingham, Alabama and the Annual National Science Teachers Association Conferences.
The science teachers constructed Learning Cycles focusing on energy related topics. A Learning Cycle has three phases: exploration, concept invention, and expansion. In the exploration phase, students participate with hands-on/minds-on activities that draw on their prior knowledge. During the concept invention phase, students find existing patterns and develop conceptual knowledge. The expansion phase allows the student to apply newly acquired knowledge or skills to other situations.
It is anticipated that the learning cycles developed in this text by Project Energy participants will enhance students' energy that the learning cycles developed in this text by Project Energy participants will enhance students' energy literacy for the 21st century.
ACKNOWLEDGMENTS
We would like to acknowledge Project Energy teachers and their students, the participating school sites, and graduate students for their input and time. We also would like to acknowledge the Department of Energy and the Alabama EPSCoR Universities for providing the necessary funding, along with the Dwight D. Eisenhower Professional Development program administered by the Alabama Commission on Higher Education.
Sample Lesson
for Grades 3-8
Dennis W.
Sunal
The University
of Alabama
Tuscaloosa,
Alabama
Alternative Conception Addressed
by the Lesson Plan: Direct sunlight is necessary for green plants to live and grow. Direct
sunlight makes green plants healthy. Green plants always need direct sunlight .
Lesson Goal: To allow students to investigate and develop inferences
about the role of sunlight in the nutritional needs of a green plant.
Prerequisites: Can measure height to the nearest millimeter or one/eighth
inch.
Exploration:
Objective: The students
will investigate the effects of sunlight on germinating seeds and young green
plants.
Materials: For each group:
Four
lima bean or corn seeds,
Potting
soil, and
Four
styrofoam cups
Procedure:
A. Organize small groups of four
students; a materials manager, a reporter, one observer, and one
illustrator. These roles could rotate
over time.
B. Describe
the materials and instructions needed for students to carry out the activity
related to the effects of sunlight on growing plants. State the key questions: Is light necessary for plants to live
and grow? Does sunlight make green plants healthy? and Do green plants always
need light?
C. Provide
each group with four lima bean or corn seeds, potting soil, and four styrofoam
cups. Ask the students to design an
experiment to test the effects of light on the growth of plants using the lima
bean or corn seeds. An example of an
experiment that might be designed by a group would involve students putting
three inches of potting soil into each cup. Then the students could plant the
lima bean seeds about one inch below the surface of the soil. They would add three tablespoons of water to
each cup. One cup would be set on the
windowsill or some bright spot in the room.
One cup would be put in a closet or in a box that is sealed off from
light. The other two cups should be put
in parts of the room that are partially lit.
One across the room from the windows and one behind or under a large
object in the room. The students would
keep a daily diary indicating at least the following observations: the date, a
description of the seed or plant, a measure of the height of the plant and the
number of leaves. The illustrator
would make a sketch of the plant each day in the diary.
An experiment such as the one above will
probably involve a week to ten days of plant growth time. Seeds generally require two to three days to
germinate (when they break through the soil) and another week to grow tall
enough to have leaves so that the effects of light become evident. The illustrator should draw the plants at
regular intervals. The observers should
record a description of the plant at the same intervals and use it to construct
a table or bar graph of plant growth.
D. At
appropriate points, the group should be allowed to discuss the results of the
experiment they designed.
Evaluation: Each group
should have a complete description of their hypothesis, procedure, data, and
results. Group skills should be
assessed by observing that students should join their groups quickly when asked
and the group should review what needs to be done before starting.
Invention:
Objective: The students
will describe the effects of sunlight on green plant growth during germination
and on green plants after they have broken through the top of the soil (after
germination).
Materials: For each student:
A lima bean
seed soaked in water for 24 hours
Procedure:
A.
Have each group present to the whole class their hypothesis, procedure, and
results. Help students communicate the
results of their activities using tables and/or bar graphs to justify their
conclusions. Continuously help the
students compare the results of each group’s experiment.
B.
Write the key questions from the exploration on the board. Ask the student
groups to discuss these questions based on the class discussion of their
experiments. Ask them to report their
answers to the whole class.
C.
Explain that the discrepancy here involves the observation that seeds will
germinate whether or not they are in the presence of light. Once germinated, the plants in the dark will
grow faster than the plants in the light.
However, they will be spindly and will have fewer leaves. If the experiment were stopped before the
plants in the dark condition die, the students will be left with the
alternative conception that light is not necessary for plants to live and
grow.
D.
Provide soaked lima bean seeds and a sheet of paper to all students. In groups, have them take apart the lima
bean seed and tape the parts to the paper.
At the bottom of the paper, ask the groups to discuss the function of
each part. As an extension, another
lesson could be performed where the students plant these parts to determine
which one grows. The students should
find the following parts: cotyledon(s), seed coat, cover, and an embryo. Tell the students that the embryo is the
plant and that the cotyledons are food sacs (starch) that the embryo uses to
develop roots and a stem with which to reach the soil surface. Corn seeds have only one food sac or
cotyledon. The students should have observed this growth during the germination
phase of the plant. State that the
germination process does not require sunlight, as they have found in their
experiments.
E.
Ask the students to display the illustrator’s pictures of plant growth
following germination in dark and light conditions. Explain to the students that even though the plants in the dark
grew faster before they started dying they did not look healthy. They did not have a very green color and
they had very few leaves. Sunlight is
necessary for the health of green plants.
It is needed by green plants in order to make green chlorophyll and to
make additional food. Without this
additional food production, the green plant’s food sac soon becomes used up and
the green plant dies because it lacks the materials and the energy that the
food provides for growth and maintenance.
F.
Closure: Light is not necessary for seeds during the germination phase of
growth. It is necessary following
germination for health and continued growth.
Evaluation: Ask the
students to create a poem about two plant seeds, one that landed on soil in a
field and one that landed on soil in a cavity under a rock or in the
woods. Assess students group skills by
observing that they stay with their group while it is working and that pay
attention to how much time they have to carry out each activity.
Expansion:
Objective: The students will solve everyday problems
involving the role of sunlight on green plant growth.
Materials: for each student:
A map or drawing of an area with three vegetation zones:
deep forest, low shrubs, and meadow (figure 1)
A sheet of paper with a 3 x 4 matrix
Procedure:
A.
Provide the following problems and ask the groups to discuss their answers and
report them to the class. The students
should provide supportive evidence for each of their responses to the
problems. Write the following problems
on the board. For problems one and two
give the students a map (it may be teacher-drawn) of an area of mixed height
and foliage. It may have an area of
deep forest, an area of small bushes, and a meadow.
1)
In which area will a squash seed planted three centimeters below the soil
surface reach the soil surface the fastest.
The temperature of the soil is the same in all areas.
2)
Small squash plants are planted in each area.
Draw the plants after 1, 2, 3, and 4 weeks. Provide each group with a 3 X 4 matrix on a whole sheet of paper.
3)
A farmer purchased an abandoned coal mine to produce mushrooms for sale in
grocery stores. The farmer spread lots of horse manure from his stables on the
floor of the coal mine. The farmer
successfully produced lots of large mushrooms for sale.
Teacher’s note: Mushrooms are part of a class of plants
called fungi. This class includes molds,
mildew, rusts, and smut. They lack
chlorophyll so they do not produce their own food. Fungi get their food from organic soil materials dissolved in
water.
B. Ask the
students to present their answers to each problem in a report to the
class. Discuss the results in an
interactive discussion.
C.
Summarize the lesson by describing each of the activities in the order in which
they were experienced in the lesson.
Briefly indicate the main point developed in each activity.
Evaluation: Each student will respond to the following
problem. The moon has a day that takes
twenty-eight of our earth days. For
fourteen earth days it is dark at a certain location on the moon and for fourteen
earth days it is light. Describe by
illustration and narrative the growth of a lima bean planted on the moon in a
greenhouse in the middle of the lunar night.
Remember that there will be two weeks of sunlight followed by two weeks
of darkness every lunar month. Describe its growth for two lunar months. identify,
investigate, and develop inferences about the role of sunlight in the
nutritional needs of a green plant.
Figure 1:
Vegetation zones.
Testing Materials for Electrical Conductivity
Sample Lesson for Grades 4-8
Clidean Epps
Russell Elementary
Russellville, Alabama
Student Misconception Addressed by the Lesson Plan: Liquids cannot be conductors.
Lesson Goal: Students will investigate electrolytes and nonelectrolytes.
Prerequisites: Students must be able to build a simple electric circuit. Students must be able to apply problem solving techniques to electric circuits.
Exploration:
Objective: Students will investigate the electrical properties of electrolytes and nonelectrolytes.
Materials: Electric circuit test (also called a conductivity tester)
Bulb, bulb holder, battery (A size or 9V)
Wires for connecting components
3 pieces of bell wire
distilled water
sugar
baking soda
vinegar
ink
lemon juice
apple juice
plastic spoons
small beakers or plastic cups to hold solutions
Procedure:
A. Place the students in groups of four and assign roles: materials manager, reader, observer, and recorder.
B. Describe materials and instructions needed for groups to carry out the activity of making a circuit tester and mixing solution.
C. State the key question: Can you find a way to predict what will happen if you put the free ends of the electric tester into a beaker of distilled water and other solutions?
D. Sample teacher led discussion: The problem is "If you put the free ends of the electric conductivity tester into a beaker of water, what will happen to the bulb? Lemon juice, apple juice, salt water, etc." Write down your predictions for each test solution. If the material is solid, place a teaspoon of each solid in half a cup/beaker of distilled water and stir.
E. Instruct the students in the construction of an electric conductivity tester. Students should investigate the conductivity of metals before they test electrolytic solutions. Attach one wire to one terminal of the bulb connector. Attach the other end of this wire to one terminal of the battery. The second wire is attached to the second terminal of the bulb and its end is left unattached to anything. The third wire is attached to the second terminal of the battery and its end is left unattached to anything. (Demonstrate each step of the procedure as the students work. Check groups for successful completion of each step.) If you have successfully constructed your circuit, the bulb is connected to the battery on only one side. Two wires are left dangling: one on one side of the bulb and the other on one side of the battery. If you touch the dangling wires for a second, the bulb should light up. If it does not, raise your hand and wait quietly for help.
Rest the dangling wires, without letting them touch each other, on the edge of the beaker/cup. Place enough distilled water into the cup so that the wires are in the water. What happens to the bulb?
Now add 1 teaspoon of salt to the water and stir. What happens to the bulb? Rinse the cup/beaker. Continue testing each of the solids and liquids.
The recorder should place a copy of the data collected in the data table for the group on the board/overhead. Each person in your group should record the results in your notebook.
Evaluation: Recorders for each group should place their results in a data table on the board or overhead. Teacher led large group discussion should cover results and conclusions drawn from the data collected.
Invention:
Objective: Students will classify common household liquids as conductors or nonconductors.
Materials: Liquid soap
Ketchup
Cola
Mustard
Syrup
4 beakers/cups
Electric conductivity tester
Paper towels
Plastic
spoon
Procedure:
A. Place students in cooperative groups and assign roles: materials manager, experimenter, observer, and recorder.
B. Teacher discussion: An electrolyte is a substance that conducts electricity when it is dissolved in water. A battery contains an electrolyte in either a liquid or paste solution. When an electrolyte dissolves, it releases equal numbers of positive and negative ions. These ions move through the solution and carry electric charges (current) between the electrodes immersed in the solution. The electrodes in your electric conductivity tester are the dangling wires.
C. Instruct students to test the liquids with the conductivity tester and record their results in their notebook. The group recorder should write results for the group on the board or overhead. Focus questions: Does the bulb light the same in each solution? Which liquids conducted electricity? Which liquids were strong conductors of electricity (strong electrolytes) and which were weak conductors of electricity (weak electrolytes)? How did you decide? Which liquids did not conduct electricity at all? How did you decide?
Closure: Explain to students that strong electrolytes release many ions and conduct electricity well. These electrolytes include strong acids and bases and most salts. Weak electrolytes do not conduct electricity as well and do not release as many ions. Sugar is a nonconductor because it does not form ions.
Evaluation: Student predictions, notebook entries, completion of tasks and group participation should be used to assess the students' performance.
Expansion:
Objective: Students will continue to test various objects for conductivity.
Procedure:
A. Place students in groups of four and assign roles: materials manager, reader, observe, and recorder.
B. Set up stations around the room and outline the procedure for moving from one station to another. Place on the board the order in which groups will rotate from one station to another. Set a time limit on each station.
Station 1: A battery contains an electrolyte in either a liquid or paste solution. Using the materials at the station, make a circuit that will light the bulb. Draw a picture of your circuit. Place the picture in your notebook. The recorder will make a copy of the picture to place on the bulletin board.
Materials: 2 bell wires (25 cm with ends stripped)
1 bulb holder
D-cell battery
Masking tape
Station 2: Classify the following mixtures as either an electrolyte or a nonelectrolyte. Describe your procedure for finding which is an electrolyte or nonelectrolyte. Draw a diagram of your circuit in your notebook. Make a data table in your notebook to record your results. The recorder should make a copy of the data on the board/overhead.
Materials: milk
orange juice
lemon juice
honey
cups
(Hint for teacher: Place the solutions in cups and label. This will reduce clean-up time.)
Station 3: You have learned an electrolyte is a substance that conducts electricity when it is dissolved in water. When something allows electricity to pass through, it is called a conductor. Use your electric conductivity tester to find out which of the solid objects at this station conduct electricity. Make a data table of your results in your notebook. The recorder will make a copy of the results on the board/overhead.
Materials: coin key
glass bobby pin
marble button
screw pencil (unsharpened)
nail pencil (one sharpened)
bar magnet pencil (both ends sharpened)
balloon pen
rubber ball eraser
Closure: Discuss the results of the stations' activities in a large teacher led discussion. Summarize key concepts of electrolytes, nonelectrolytes, batteries, conductors, and nonconductors.
Evaluation: Ask students to define and give examples of electrolytes and nonelectrolytes. Ask students to define and give examples of conductors and nonconductors. Ask students to define a battery and to draw a circuit that will light a bulb.
[Back to Table of Contents]
Conductors, Insulators, and Semiconductors
Sample Lesson for Grades 6-12
Dennis W. Sunal
The University of Alabama
Tuscaloosa, Alabama
Student
Alternative Conceptions (Misconceptions) Addressed by the Lesson:
1. A conductive material always conducts electricity.
2. Conductors cannot change their
conductivity.
2. Lights can only by turned off and on with a switch.
3. Only incandescent bulbs produce light in an electrical circuit.
Lesson Goal:
Students will investigate the differences in conductivity of materials,
design a variety of complete circuits, and observe the differences between the
manner in which light is produced in an incandescent
light bulb, and an LED.
Prerequisites: Students are familiar with the concepts of an electric circuit, metal and nonmetal, charged particle, and solution. Students should be able to light a bulb using a battery, and a wire.
Content Accommodations: State Standards: Grade 6:
#26-28,46-49, 51, 52; Grade 7: #38-41, 56-60, 62, Grade 9: #43-45, 61-64, HS
Physics: #25-34, 55-58 (from Alabama
Course of Study- Science). No additional areas need to be added.
Safety Accommodations: Students should be warned about touching wires that are
warm (short circuit) and not to taste any substance.
Exploration :
Objectives:
Students will make predictions and then test them regarding conductivity in solids and liquids.
Students will make conductivity predictions of the various materials (solid or liquid), design a conductivity test, and record observations of the results.
Students will describe differences in properties between conductors and semiconductors.
Materials: For each group:
one 9-volt battery
one 12-volt light bulb with pig tails
one 14-volt LED with leads
samples of conductors
samples of insulators
samples of semiconductors from kit (optional)
separate beakers containing:
distilled water
distilled water + salt
distilled water + sugar
paper towels
beaker of distilled water for rinsing connectors
paper for recording results
Procedure:
A.
Place the students in groups of four and assign roles: materials manager, observers (two),
and a data recorder.
B. 1. Describe the materials and instructions
needed for the groups to carry out the activity
of testing the conductivity
of various materials in C and D below.
2. Distribute batteries, bulbs, and wires to the groups.
3. Have the students light the bulb in a simple circuit.
C. 1.
State the key questions: “What solids
allow the bulb to light?” “Can liquids
allow the
bulb to light?” Can you find a
way to guess, or predict, why some of the materials
allowed the bulb to light, and
some did not?” Use the same questions
concerning an
LED.
2. Decide predictions and write them down. Then, begin the group activity
D. Ask the groups to do the following activity and write down what they find. The data could be recorded in a data table.
1. Begin by asking the question: “Can you construct a circuit so that the bulb
can be lit
and use this circuit to test which
materials are conductors, and which are insulators?”
2. Test a variety of materials by
placing them in the circuit (make sure that the rest of the
circuit remains intact). You might begin with a penny, and then
replace the penny with
a variety of materials. Rate the conductivity as good, poor, or
none.
3. Next, using the beakers of liquid, test to see which solutions allow the bulb to light .
In each test, the probes in the solution should be kept the same
distance apart. After
each test, be sure to rinse the
probe wires in the plain non-testing distilled water and
dry them. Remember, the solutions are to be placed in the same position as
the solid
materials were in the circuit. Once again, record the conductivity as good,
poor, or
none.
E. Continue with the following activity in the groups: Ask them to;
1. Construct a simple circuit with
the battery, LED, and connectors. Make
sure
the LED lights.
2. Reverse the poles connecting to the LED.
3. Record the results.
4. End with the question: “Why did the conductor (LED) only light when
the
leads were connected in one way?”
F. Ask each group to
discuss the results of Activity D and E, and the questions from
Activity C.1. and E.2.
above.
Evaluation: Each group of students will have completed all predictions for the Exploration activities. Their predictions should be evaluated for their prior knowledge and you should monitor their participation in the group by observing if the groups stay together while working, and each person performed their assigned role in the activity.
Invention :
Objective: The students will use their concept of semiconductive materials to demonstrate how diodes work in a simple circuit and in testing conductivity.
Materials: To be given to each member of the class:
Diagram of a diode
Handout covering semiconductive materials and diode construction
For each group:
one 9-volt battery
one 14-volt LED with leads
samples of conductors
samples of insulators
samples of semiconductors from kit (optional)
separate beakers containing:
distilled water
distilled water + salt
distilled water + sugar
paper towels
beaker of distilled water for rinsing connectors
paper for recording results
Procedure:
A. Place the students in groups of four as was done in the exploration
B.
Have the groups present their answers to the questions posed in the
Exploration.
C.
Discuss the various answers as a whole class, writing the responses on
the
board, if so desired. Ask students for their ideas as to why the
diodes worked
only part of the time.
D.
Discuss operational definitions of conductors and non-conductors;
include the
direction of electron flow in a DC circuit.
E.
Hand out the diode diagrams and the semiconductor fact sheet. Discuss these
with the whole class. Describe the properties of semiconductors
with the class.
Allow the groups to work on the
questions located on the diode diagrams.
F.
Ask the class the following thought questions: “Why did the distilled water not
work as a conductor, but the
distilled water + salt worked well?”
“Which lead
of a LED represents the n
region, and which one represents the p
region?”
G. Repeat this
activity: Describe for the students the materials and instructions
needed for student groups to carry-out
the activity of connecting the power
source to a light bulb and an
LED.
1. State the key question: “Are the properties of a light bulb and an
LED the same
in terms of circuit requirements?”
2.
Here is the problem: If you
connect the battery to the light bulb, does it matter
which poles of the battery are used? What about the LED? Make a prediction
of the outcome.
3.
Ask the students to follow these directions. Try out your guess using the 9-volt
battery, the 12-volt bulb with
pigtails, and the 14-volt LED with leads.
If your
guess didn’t work, try to decide why
based on your knowledge of conductors,
insulators, and semiconductors. Record all work.
4. End with the question: “Why did the LED only light when the leads
were
connected in one way?” Have the groups discuss their answers. Refer to the
hand outs.
H. Repeat the
procedures from Activities C and D in the Exploration using the LED
instead of the bulb.(note:
reversing the lead of a diode will cause the LED not to light,
even with a conductor in the
circuit). Ask the groups to do the
following activity and
write down what they find. The data could be recorded in a data table.
1. Begin by asking the question:
“Can you construct a circuit so that the LED can be lit
and use this circuit to test which materials are conductors, and
which are insulators?”
2. Test a variety of materials by placing them in the circuit (make sure
that the rest of
the circuit remains intact). You might begin with a penny, and then
replace the penny
with a variety of materials. Rate the conductivity as good, poor, or
none.
3. Next, using the beakers of liquid, test to see which solutions allow the LED to light .
In each test, the probes in the solution should be kept the same
distance apart.
After each test, be sure to rinse
the probe wires in the plain non-testing
distilled water and dry them. Remember, the solutions are to be placed in the
same position as the solid
materials were in the circuit. Once
again, record the
conductivity as good, poor, or
none. Have the groups discuss their answers.
Closure: See student handouts 1 and 2.
Expansion :
Objective: The students will apply their knowledge of conductors, insulators and semiconductors to construct circuits using an LED and a light bulb and describe how these ideas are used in everyday life.
Material: For each group:
one 9-volt battery
one 12-volt bulb with pigtails
one 14-volt LED with connecting leads
Procedure:
A.
Place the students in groups of four and assign roles: materials manager,
observers (two students), and a
recorder.
B. Describe for the students the
materials and instructions needed for student
groups to carry-out the activity of
connecting the power source to the light
bulbs and LED’s. Ask the students to
construct one series and one parallel
circuit using both the bulb, and the
LED.
Ask them to construct a series/parallel circuit of their own
design. They should
diagram and explain how
each circuit performed.
C. Student groups should also
discuss and describe how semiconductors can be
used in everyday electronic
devices.
D. Discuss the results of the
groups with the whole class. The teacher
can
summarize the results on
the board.
E.
Summarize the results by stating that at the beginning of the
activities, the
students may not have known the
real difference between a conductor,
insulator, and a semiconductor. By making circuits with different
materials,
they should be able to apply these
terms to everyday objects. They should
also
be able to able to describe how
semiconductors can be used in everyday
electronic devices.
Evaluation: Have the students work in their groups to come up with an answer to the following question: “How can semiconductors be used as switches in a computer?” Have the groups write down their answers to turn in.
Student Handout #1
Semiconductor
Fact Sheet
Semiconductors
A semiconductor is composed of
substances such as silicon or germanium that have electrical conductivity
capabilities in between that of an insulator
and a conductor. They can either resist or easily pass the
flow of electric current. One area of a
piece of silicon can be chemically treated with phosphorus, arsenic, or
antimony to make a region which has extra electrons, called n type.
However, if we treat silicon with boron, indium, or aluminum, it has a
lack of electrons, and is called p
type.
The
Semiconductor Diode
The semiconductor diode is a two
terminal device. In one direction,
through the device from the p to the n region, the diode conducts readily,
presenting low resistance to current flow.
In the opposite direction the semiconductor diode presents a high
resistance to current flow.
A pn diode consists of a single block of semiconductive material to
which two leads are connected. One of
the leads is connected to the n
material, in which there are numerous electrons which carry current. The second lead is connected to the p material easily by the motion of
electrons through it.
The plane separating the p material from the n material inside the diode is called the pn junction. When voltage
is added to the system, there is a flow of current into and out of the
junction.
Student Handout #2
THE SEMICONDUCTIVE DIODE
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