Download 39. A Simple Motor

iv
act ity
39
A Simple Motor
BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN
Grade 4—Quarter 4
Activity 39
SC.C.2.2.1
The student recognizes that forces of gravity, magnetism, and electricity operate simple
machines.
SC.H.1.2.2
The student knows that a successful method to explore the natural world is to observe and
record, and then analyze and communicate the results.
SC.H.1.2.3
The student knows that to work collaboratively, all team members should be free to reach,
explain, and justify their own individual conclusions.
SC.H.1.2.4
The student knows that to compare and contrast observations and results is an essential
skill in science.
SC.H.1.2.5
The student knows that a model of something is different from the real thing, but can be
used to learn something about the real thing.
© Delta Education. Photocopying and distribution prohibited.
ACTIVITY ASSESSMENT OPPORTUNITIES
The following suggestions are intended to help identify major concepts covered in the activity
that may need extra reinforcement. The goal is to provide opportunities to assess student
progress without creating the need for a separate, formal assessment session (or activity) for
each of the 40 hands-on activities at this grade level.
1. Remind students that they were again acting as engineers in this activity. Ask, What do
engineers do? (They solve problems by designing and building devices.) Remind students
that they were given a chance to try out new engineering ideas in Step 8. Tell them to
make a list with three columns labeled, “What we tried,” “What we expected,” and “What
we noticed.” For each engineering idea or change they made, have students complete a
row in their chart. (Answers will vary based on the materials available, time allotted, and
inventiveness of the students.)
2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the
activity.
In addition to the above assessment suggestions, the questions in bold and tasks that
students perform throughout the activity provide opportunities to identify areas that may
require additional review before proceeding further with the activity.
broward county hands-on science Quarter 4
423
424
© Delta Education. Photocopying and distribution prohibited.
activity 39 A Simple Motor
iv
act ity
39
A Simple Motor
4
1 pc
OBJECTIVES
Students apply their knowledge of electric
current and electromagnetism to construct a
simple motor.
For the class
8
16
16
1
1 roll
1 roll
1 roll
16 pcs
1 pair
The students
construct a simple motor
describe the relationship between electric
current and magnetism in a simple motor
trace the path of electric current in a
simple motor
SCHEDULE
rubber grommet spacers
wire, plastic-insulated, 25-cm
batteries, D-cell
electrical clips
magnets, rubberized
ruler, metric
tape, masking
wire, enamel-coated
wire, plastic-insulated
wire, plastic-insulated, 15-cm
wire cutters
*provided by the teacher
About 1 hour
VOCABULARY
armature
mechanical energy
motor
permanent magnet
PREPARATION
1
Make a copy of Activity Sheet 39 for each
student.
2
From the roll of plastic-insulated wire, cut
two 10-cm (4-in.) pieces for each team.
Use the wire cutters to strip the insulation
off the entire length of each wire. Also cut
one additional 25-cm (10-in.) piece of wire
for each team and strip just the ends of
these pieces. From the roll of enamelcoated wire, cut one piece 30 cm (about
1 ft) in length for each team.
3
Each team of four will need a plastic base,
one battery, two electrical clips, one piece
of emery cloth, four rubber spacers, two
Fahnestock clips, one rubberized magnet,
four paper fasteners, two bare 10-cm
wires, one 30-cm piece of enamel-coated
wire, a piece of masking tape, and two
25-cm pieces of plastic-insulated wire.
4
Have extra batteries, electrical clips,
rubberized magnets, and 15-cm (6-in.)
© Delta Education. Photocopying and distribution prohibited.
MATERIALS
For each student
1
Activity Sheet 39
1 pair
safety goggles*
For each team of four
1
1
2
1
2
1
4
battery, D-cell
Delta CircuitworksTM base
electrical clips
emery cloth
Fahnestock clips
magnet, rubberized
paper fasteners
broward county hands-on science Quarter 4
425
BACKGROUND INFORMATION
A motor is a device that transforms any kind
of energy into mechanical energy. A motor in
its simplest form is merely a single coil of wire
(an armature) that, when connected to an
electrical energy source, creates an
electromagnetic field. When the
electromagnetic field of the coil interacts with
the magnetic field of a permanent magnet,
the attraction and repulsion between the two
fields causes the coil of wire to rotate. In this
activity, students will observe what happens
when the magnetic fields of an electromagnet
and a permanent magnet interact.
lengths of wire available for those
students who wish to vary their
experiments.
Activity Sheet 39
A Simple Motor
1. Use the paper fasteners and
rubber spacers to hold the ends
of the wire supports and the two
Fahnestock clips to the base. The
wires should be positioned so that
they form inverted “U”s. Position
the armature into the looped
supports. Tape a rubberized
magnet flat under the coil.
2. Insert the battery and electrical clips
into the base. Use the 25-cm pieces of
plastic-insulated wire to connect the
battery to the Fahnestock clips on the
armature supports. The armature may
need a slight tap to start it moving.
3. Experiment by adding more rubberized magnets and batteries to the setup.
What did you observe when you increased the number of rubberized magnets?
The armature spun faster.
What did you observe when you increased the number of batteries?
The armature spun faster.
4. Optional Activity Pair up with another team and pool your materials. Replace
your team’s rubberized magnet with the other team’s coil. Tape the coil in
position and connect it to its own battery source. What happens?
The armature spun.
1
Write the words motor and electromagnet on
the board. Tell the students that they are
going to apply what they have learned about
the effects of electromagnetism in the
previous activity to build a simple motor.
2
Write the word armature on the board.
Explain that an armature is a coil of wire in a
motor. When electric current passes through
the wire coil it creates a magnetic field that
interacts with the magnetic field of the
permanent magnets in the motor. This
interaction causes the armature to move.
Explain that a permanent magnet, unlike a
temporary magnet, retains or keeps its
magnetism for a long time.
426
activity 39 A Simple Motor
Additional Information
The simple motor constructed in this activity
illustrates how continuous motion is possible
when the magnetic fields of an electromagnet and a permanent magnet interact.
In Activity 40, students will construct a more
complex motor—one that functions more like
a real motor.
© Delta Education. Photocopying and distribution prohibited.
Guiding the Activity
Guiding the Activity
Additional Information
Demonstrate for the class how to construct
the armature by wrapping the 30-cm (about
1-ft) piece of enamel-coated wire around a
rubberized magnet. Slide the coil off the
rubberized magnet and loop each end of the
wire around the coil two times to hold it
together (see Figure 39-1). Gently sand the
enamel coating off the entire length of each
end of wire, being careful not to deform the
coil. This is done so that later, when the
armature is inserted into the supports, bare
wire will be touching bare wire.
3
© Delta Education. Photocopying and distribution prohibited.
4
Figure 39-1. The armature.
Figure 39-2. Supports for the armature.
Demonstrate for the class how to make a
loop in the middle of a 10-cm (4-in.) piece of
bare wire by wrapping it once around a
pencil. Two such wires will become the
supports for the armature (see Figure 39-2).
Distribute to each team a rubberized magnet,
two 10-cm (4-in.) pieces of bare wire, a piece
of emery cloth, and the 30-cm piece of
enamel-coated wire. If needed, assist the
students in the construction of the armature
and supports.
broward county hands-on science Quarter 4
427
Guiding the Activity
5
Additional Information
Distribute Activity Sheet 39 to each student,
and a base, battery, two electrical clips, two
Fahnestock clips, four rubber spacers, four
paper fasteners, a piece of masking tape, and
the two 25-cm (10-in.) pieces of wire to each
team. Have them complete steps 1 and 2 on
the activity sheet. Assist students, as needed,
in the construction of their simple motors
(see Figure 39-3).
As necessary, explain that motors are
devices that change any kind of energy into
mechanical energy, or the energy to make an
object move.
6
In the event that a motor does not work, ask,
Why do you think your motor doesn’t work
well? What would you change to improve
how it functions?
7
After students have gotten their motors
running, ask, Why does the armature rotate?
428
activity 39 A Simple Motor
Figure 39-3. A simple motor.
Have the student teams work together to
review their setups and compare them with
the diagram on the activity sheet. Give the
students these tips:
a. Make sure that both ends of the armature
have been sanded bare and that these
bare ends are making contact with the
loops of the bare wire supports.
b. Check that the paper fasteners are tight
enough against the rubber spacers so that
the Fahnestock clips make good contact
with the bare wire supports.
c. Check that the battery is fresh.
Remind students that magnets can repel or
attract each other. Help students understand
that the armature rotates when the magnetic
field of the temporary magnet (the wire coil)
interacts with the magnetic field of the
permanent magnet taped below it.
© Delta Education. Photocopying and distribution prohibited.
Guiding the Activity
Why doesn’t the permanent magnet simply
attract or repel the armature?
8
By bouncing in the loops, the armature is
constantly making and breaking electrical
contact. This electrical “on and off ” produces
intermittent electromagnetism in the
armature. This is what causes the armature
to rotate.
Encourage the students to experiment with
their motors. Provide whatever additional
materials, such as magnets and batteries,
they might need.
REINFORCEMENT
Have the students trace the path of electric
current in a simple motor from the negative
end of the battery, through each circuit
element, back to the battery. Be sure that the
path they trace takes into account the
interaction between the electromagnetic field
of the armature and the magnetic field of the
permanent magnet and that this interaction
is what causes the armature to rotate.
SCIENCE JOURNALS
Have students place their completed activity
sheets in their science journals.
© Delta Education. Photocopying and distribution prohibited.
Additional Information
CLEANUP
Tell the students to disassemble their
simple motors and to return the materials
to the kit.
SCIENCE AT HOME
Ask the students to identify some of the
small electric motors that are used in the
home and to imagine how the tasks would
have been performed before the motor was
invented. Students may choose hair dryers,
blenders, can openers, vacuum cleaners,
and so forth.
broward county hands-on science Quarter 4
429
Science Challenge
Science, Technology, and Society
If you or your students have access to small
electric motors—such as motors that run toy
race cars—that no longer work, let students
take them apart. Guide them as needed to
identify the parts of the motors that
correspond to the parts of the simple motor
they built. Store each disassembled motor in
a separate container for use in the next
Science Challenge.
The miniaturization of electric motors has
had an impact on scientific research. For
example, small, lightweight motors assist
in space and undersea exploration.
Encourage interested students to
investigate how miniaturized motors
are used.
A transformer increases or decreases the
voltage, or “strength,” of an electric
current flowing from a power source to an
electrical device. Transformers usually
incorporate a square loop of iron with two
coils of wire on opposite sides of the loop.
An electric current flows from a power
source into one coil, causing the iron loop
to become an electromagnet. The
electromagnetism causes electrons to flow
in the second coil. If the second coil has
more turns of wire than the first coil, the
voltage going out of the transformer and to
the electrical device is increased; this type
of transformer is called a step-up
transformer. If the second coil has fewer
turns of wire than the first coil, the voltage
going out is decreased; this type of
transformer is called a step-down
transformer. Step-down transformers are
commonly used to decrease the voltage for
home appliances and toys such as electric
trains and slot-car sets.
Science Extension
Ask students to describe the change in
forms of energy that they observed with
their simple motor. The chemical energy in
the battery is changed to electrical energy,
which is changed to mechanical energy—
the energy of motion—in the rotation of
the armature.
Ask students to suggest other forms of
energy besides electrical energy that are
used to produce motion, and have them
give specific examples of such motors. For
example, converting chemical energy to
mechanical energy (automobiles, lawn
mowers, and chain saws).
Science and Social Studies
Prompt students to try to imagine what
everyday life was like before electricity and
devices that run on electric motors were
available to everyone. What daily tasks
would have been more difficult, more timeconsuming, or perhaps even impossible?
Have student volunteers role-play the preand post-electricity ways of performing a
task.
430
activity 39 A Simple Motor
Ask students to identify toys, games, and
other devices in their homes that require a
transformer to operate correctly. Why is a
transformer needed for each device?
Encourage students to research how
transformers work and the types that are
used. How are transformers used in the
electric power industry?
© Delta Education. Photocopying and distribution prohibited.
Connections