Download Electromagnets - Stout Middle School

Electricity and Magnetism
Electromagnets
Purpose
To construct an electromagnet and change its strength
by manipulating different variables.
Process Skills
Observe, measure, form a hypothesis, collect data,
interpret data, identify and control variables,
communicate, draw conclusions
Background
Magnetism is an invisible force caused by moving
electrons. Magnets form when those electrons line up,
creating magnetic force at opposite (north and south)
poles. An object that has been magnetized will attract
ferrous metals (such as iron, cobalt, and nickel).
Materials
q data sheet
q 2 non-galvanized steel
nails, 10 cm (4 in.)
q 2 non-galvanized steel
nails, 5 cm (2 in.)
q 2 lengths of thinly
insulated, 20-gauge wire,
30 cm (1 ft.)
q 2 lengths of thinly
insulated, 20-gauge wire,
60 cm (2 ft.)
q wire strippers or scissors
q 2 new D-cell batteries
q 30 folded staples
q electrical tape
Permanent magnets, such as the ones on your
refrigerator, keep their magnetism for a long time.
Temporary magnets do not keep their magnetic properties over an extended period
of time. One type of temporary magnet is an electromagnet. When it is properly
connected to an electric current, the electrons within the electromagnet line up,
creating a magnetic field. The magnetic field
of an electromagnet can be turned on and off,
depending on whether or not it is connected
to an electric current. In this exploration, you
+
will make an electromagnet and determine
how different variables can affect its strength.
Safety: Electromagnets can become hot very
quickly. Use caution when touching your
electromagnet! Use cloth gloves if available.
Disconnect wires from batteries at all times
when they are not in use.
Time – About 1 hour
Grouping – Small groups and individuals
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Electricity and Magnetism—Electromagnets
Procedure
Making Electromagnets
1.Your teacher may choose to remove the
insulation from the wire ends ahead of
time. If not, do so very carefully. Use the
wire strippers or scissors to carefully
remove about 2 cm (1 in.) of insulation
from each end of all four wires. The
exposed ends of each wire will later be
connected to the batteries.
2.Wrap one of the 30 cm pieces of wire
around a 5 cm nail 10 times. Wrap the
wire tightly and neatly (see Figure A),
and make sure that it is coiled in a
single direction. Be sure the coils do
not overlap. Leave some loose wire
at each end of the nail.
5 cm nail with 10 wire coils
10 cm nail with 10 wire coils
5 cm nail with 20 wire coils
10 cm nail with 20 wire coils
Hypothesis: In this activity, you will
conduct tests to find out how many
staples different electromagnets can pick
up. You will use three variables to make
electromagnets: length of nail (5 cm or 10 cm),
number of wire coils around the nail (10 or
20), and number of D-cell batteries (1 or 2).
With your group, discuss which of the eight
possible combinations of variables you
predict will pick up the most and the fewest
staples, and why. Then complete the
hypotheses on your own data sheet.
Test 1: Electromagnets with One Battery
steel nail
exposed wire
insulated wire
1.Pile 30 folded staples in your
work area.
2.Pick up the 5 cm nail that has 10 wire
coils. Tape one end of the exposed
wire to each end of one D-cell battery
(see Figure B). The tape must be strong
enough to hold onto the nail in midair.
Your nail is now an electromagnet!
Figure A
3.Repeat Step 2, using your other 30 cm
piece of wire, but using a 10 cm nail
instead. Wrap the wire in 10 coils.
D-cell battery
4.Now repeat Step 2, but wrap a 60 cm
piece of wire around each of the
remaining 5 cm and 10 cm nails. This
time, wrap the wire in 20 coils. Once
again, leave some loose wire at each
end of the nail. You should now have
the following nail-wire combinations:
tape
+
steel nail
insulated wire
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2
-
exposed wire
Figure B
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Electricity and Magnetism—Electromagnets
Test 2: Electromagnets with Two Batteries
3.Hold onto the battery, letting the
coiled nail hang below it. Slowly move
the nail around in the pile of staples
for 5 seconds and then raise it above
the pile. In a nearby area, remove
the staples from your electromagnet.
[Note: Immediately after removing the
staples, disconnect one end of the wire
from the battery. The longer you leave
it connected, the hotter the wire will
become!] Count the number of staples
your electromagnet picked up. Record
this number in the first table on your
data sheet, on the appropriate row,
under Trial 1.
1.Now you will repeat the entire
exploration, but use two D-cell
batteries instead of one. Pick up the
5 cm nail that has 10 wire coils. Tape
one end of the exposed wire to one
of the battery’s positive ends (the end
with the + sign). Tape the other end
of the exposed wire to the second
battery’s negative end (the end with
the – sign). Hold onto both batteries
so that the first battery’s negative end
touches the second battery’s positive
end (see Figure C). You now have a
new type of electromagnet.
4.Repeat this test two more times
with the same electromagnet. [Note:
Remember to disconnect one end of
the wire from the battery as soon as you
have removed the staples each time!]
Record the results under Trial 2 and
Trial 3 for this type of electromagnet.
+
-
+
-
exposed wire
5.Add together the number of staples the
electromagnet picked up in Trials 1, 2,
and 3. Divide the total by 3. Record this
number as the Average on the correct
row of the data table.
steel nail
6.Repeat Steps 1–5 using the 10 cm nail
with 10 coils, then the 5 cm nail with
20 coils, and finally the 10 cm nail
with 20 coils. [Note: Remember to
disconnect one end of the wire from
the battery as soon as you have removed
the staples each time!]
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tape
D-cell battery
3
Figure C
insulated wire
2.Repeat Test 1, but this time use the two
connected batteries as you test each of
your four coiled nails. Complete three
trials with each electromagnet, and
record all data in the second table on
your data sheet.
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Electricity and Magnetism—Electromagnets Data Sheet
Name________________________________________ Date_____________
Hypotheses: Consider all the variable combinations in this activity (5 cm or 10 cm nail
length, 10 or 20 wire coils, 1 or 2 batteries) and then complete each hypothesis.
1. Which combination of variables will pick up the most staples? Why do you think this
will be so?
2. W
hich combination of variables will pick up the fewest staples? Why do you think this
will be so?
Collect Data
Test 1: Number of staples picked up when connected to one battery
Electromagnet
description
Trial 1
Trial 2
Trial 3
Average
5 cm nail with
10 coils
10 cm nail with
10 coils
5 cm nail with
20 coils
10 cm nail with
20 coils
Test 2: Number of staples picked up when connected to two batteries
Electromagnet
description
Trial 1
Trial 2
Trial 3
Average
5 cm nail with
10 coils
10 cm nail with
10 coils
5 cm nail with
20 coils
10 cm nail with
20 coils
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Electricity and Magnetism—Electromagnets Questions
Name________________________________________ Date_____________
Analyze Data
1. When your results were averaged, which combination of three variables made your
electromagnet pick up the most staples?
2. When your results were averaged, which combination of three variables made your
electromagnet pick up the fewest staples?
3. Which variable affected the results most—nail length, number of coils, or number
of batteries? Why do you think this variable was so important?
4. Which variable affected the results least—nail length, number of coils, or number
of batteries? Why do you think this variable was not as important as the others?
5. Why was it important to conduct three trials with each electromagnet and find the
average results?
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Electricity and Magnetism—Electromagnets Questions
Name________________________________________ Date_____________
Draw Conclusions
1. Would the electromagnets have worked if you had used a piece of wood or plastic
instead of a nail? Why or why not?
2. Why did the safety tips suggest disconnecting just one wire from the battery instead
of both wires?
3. How would you build an electromagnet that was stronger than any of the ones you
used in this activity?
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Electricity and Magnetism
Electromagnets
Teaching Tips
These process activities will help students understand the properties of electricity
and magnetism, and the relationship between these two forces. Electricity can be
observed in action both as static electricity and as an electric current. Magnetism
can be applied to many familiar objects, but many other objects are not magnetic.
Exploring and experimenting with variables will allow students to understand that
electricity and magnetism can each be used at differing strengths and in different
applications. When using electromagnetism, safety is extremely important.
Set-up and
procedures
efore students test the electromagnets, you may want to conduct your
B
own investigation so you will be able to judge whether students’ results
are accurate, given the available materials.
¢ Discuss the importance of wrapping the wire around the nails neatly
and in the same direction. If students change the direction of their
wrapping partway through, the electrons will not all align in the same direction. This will decrease the strength of the electromagnet.
¢ For increased safety during the experiment, you may wish to strip
the insulation off the ends of the wires beforehand. Use wire cutters to carefully pull about 2 cm (1 in.) of insulation from each end, creating
leads of exposed wire.
¢ It doesn’t matter which end of the wire is connected to the battery
in terms of magnetic strength. View the wire as neutral. What will vary is the polarity (north versus south pole) of the electromagnet and the flow of electric current.
¢ To avoid distraction and maximize lab safety, pass out materials
only after students have finished reading through their instructions and making their hypotheses.
¢
I f using cooperative groups, assign jobs for each student within
each group. Examples include getter, recorder, wire wrapper, staple counter, materials manager, and reporter.
¢ Reinforce relevant vocabulary terms (e.g., electromagnet, magnetic
field, electric current) throughout the experiment.
safety
¢
¢
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iscuss all safety rules prior to allowing students to begin the experiment.
D
Emphasize the importance of disconnecting the wires from the batteries
immediately after collection of data.
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materials
extensions and
variations
Electricity and Magnetism—Electromagnets
¢
The
best wire to use for this experiment is magnet wire, available
in electronics and hardware shops. Other types of wire, including standard electrical wire and telephone wire, will also work.
¢ Do not use galvanized nails.
¢ Have extra materials available in case of dead/weak batteries,
overly stripped wire, or other material faults.
¢ Different sizes of batteries, different lengths of wire, and different sizes
of nails can all be substituted in this experiment. Results will vary, and
student data sheets will need to be adjusted accordingly. Remember that if stronger batteries are used, the wires will heat up faster.
¢
Variation/Inquiry
¢
Research/Technology:
¢
¢
¢
¢
¢
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Science: Repeat the experiment, but this time provide
each group with different sizes of batteries, such as AAA, AA, C, and 9-volt. How do different sizes of batteries affect the results?
Have students research how magnets work
and the many uses of magnets, including electromagnets. Ask them to compile and present their research in a digital slideshow to share with other classes.
ESL/ELL: Have students create a dictionary or word wall in which key
vocabulary words are alphabetized, defined, and illustrated, such as:
magnetism, force, electrons, north pole, south pole, metal, iron, permanent,
temporary, electromagnet, electric current, and magnetic field.
Home Connection/Technology: Have students search and list everything
in their house that uses magnets. Compile all students’ lists into a class list. Then students can find or create images of each magnetic item to contribute to a class bulletin board or mural about magnets.
Guest: Invite a radiologist to visit the class to discuss how magnets
are used in medicine.
Field Trip: Visit a power plant or recycling center. Ask a technician
to explain the roles that magnets play.
Research: See Using the Internet in the Unit Guide for suggested websites
to extend the learning.
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Electricity and Magnetism—Electromagnets Data Sheet
Answer key
experiment
Electricity and Magnetism—Electromagnets Data Sheet
Name________________________________________ Date_____________
Hypotheses: Consider all the variable combinations in this activity (5 cm or 10 cm nail
length, 10 or 20 wire coils, 1 or 2 batteries) and then complete each hypothesis.
1. Which combination of variables will pick up the most staples? Why do you think this
will be so?
Hypotheses will vary and should be supported by logical reasoning.
2. W
hich combination of variables will pick up the fewest staples? Why do you think this
will be so?
Hypotheses will vary and should be supported by logical reasoning.
Collect Data
Test 1: Number of staples picked up when connected to one battery
Electromagnet
description
5 cm nail with
10 coils
10 cm nail with
10 coils
5 cm nail with
20 coils
10 cm nail with
20 coils
Trial 1
Trial 2
Trial 3
Results will vary, depending on the materials used.
The number of staples listed under each trial may vary
within each row but should be similar. In Test 1 (one
battery), the combination of variables that picks up the
greatest number of staples is likely to be the 10 cm nail
with 20 coils.
Average
Each response
should
accurately
calculate the
average of
Trials 1, 2, and
3 on each row.
Test 2: Number of staples picked up when connected to two batteries
Electromagnet
description
5 cm nail with
10 coils
10 cm nail with
10 coils
5 cm nail with
20 coils
10 cm nail with
20 coils
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Trial 1
Trial 2
Trial 3
Results will vary, depending on the materials used and
how well the batteries are connected. The number of
staples listed under each trial may vary within each row
but should be similar. In Test 2 (two batteries), the
combination of variables that picks up the greatest
number of staples should, in theory, be the 10 cm nail
with 20 coils because greater current should yield a
stronger electromagnet. But in practice, results may vary.
4
Average
Each response
should
accurately
calculate the
average of
Trials 1, 2, and
3 on each row.
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Electricity and Magnetism—Electromagnets Questions
Answer key and explanations
Analyze Data
1. W
hen your results were averaged, which combination of three variables made your
electromagnet pick up the most staples?
Results will vary but should accurately reflect an analysis of the recorded data.
2. W
hen your results were averaged, which combination of three variables made your
electromagnet pick up the fewest staples?
Results will vary but should accurately reflect an analysis of the recorded data.
3. W
hich variable affected the results most—nail length, number of coils, or number
of batteries? Why do you think this variable was so important?
Results will vary but should accurately reflect an analysis of the recorded data. The number of coils
may affect the results most. When more coils are added around the core of the electromagnet, more
electrons in the nail are polarized, resulting in a stronger magnet. The number of batteries might
have an even greater impact on the results, but the flow of current from one battery to the next can
be affected by how well they are held together during Test 2.
4. W
hich variable affected the results least—nail length, number of coils, or number
of batteries? Why do you think this variable was not as important as the others?
Results will vary but should accurately reflect an analysis of the recorded data. Nail length may
affect the results least. The number of coils and number of batteries have a greater impact on
the amount of electric current passing through the nail, resulting in a stronger magnet.
5. W
hy was it important to conduct three trials with each electromagnet and find the
average results?
Ideally, at least three trials should be conducted in a science investigation to ensure that results
are reliable. More trials reduce the chances of drawing conclusions based on quirks and errors,
and increase the potential accuracy of measurement.
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Electricity and Magnetism—Electromagnets Questions
answer key and explanations
Draw Conclusions
1. W
ould the electromagnets have worked if you had used a piece of wood or plastic instead
of a nail? Why or why not?
The electromagnets would not have worked. A ferrous metal—such as iron, cobalt, or nickel—
must be used to allow electric current to create a magnetic field around the core material.
2. W
hy did the safety tips suggest disconnecting just one wire from the battery instead
of both wires?
The electromagnet has a current running through it only when both wires are connected.
Disconnecting just one wire breaks the circuit and stops the flow of electricity, so disconnecting
both wires is not necessary.
3. H
ow would you build an electromagnet that was stronger than any of the ones you used
in this activity?
Answers will vary but may include: use stronger batteries, use more batteries, wrap the coil around
the nail more times, use a longer nail, use a thicker nail, or use a thinner nail. (These responses may
be a good starting point for further inquiry into building electromagnets. However, always monitor
the introduction of new variables for safety!)
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