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Electromagnets
Tanya English
8435 Constance
Chicago IL 60617
(312) 734-1301
O'Keeffe Elementary School
6940 South Merrill Avenue
Chicago IL 60649
(312) 535-0600
Objectives:
Grade Level: 3-4
The students will make an electromagnet that will attract a metal
object.
The students will increase the strength of an electromagnet so that it
will
attract an increased number of metal objects.
The students will compare the properties of magnets and electromagnets.
Materials Needed:
For 20 students.
10--20 inch strips of insulated copper wire, 1/2 exposed on each end
10--40 inch strips of insulated copper wire, 1/2 exposed on each end
15--size "D" batteries
1--battery holder for 2 "D" batteries
10--compasses
25--iron nails, 4" long
1--box of paper clips, approx. 300
masking or transparent tape
iron filings
5" x 7" index card or clear transparency
Strategies/Activities:
Activity #1:
Give each pair of students one battery, iron nail, 40" copper wire, and
about 30
paper clips. Have them, using only the nail, try to pick up as many
paper clips
as possible. Discuss methods and results. Then instruct them to wrap
the
copper wire around the nail ten times leaving 5-6 inches of wire free
on each
end of the nail. Attach one end of the wire to the negative pole of
the
battery. Tape securely and then touch the other end of the wire to the
positive
pole of the battery while their partner uses the nail to pick up paper
clips.
Then release the wire from the positive pole of the battery. Discuss
methods
and results. Record the number of paper clips picked up by the
magnetized nail
by each group.
Concept: Electric current flowing through a wire creates a magnetic
field which
caused the iron nail to become a temporary magnet. When the electric
current is
cut off, the nails loses its magnetic property and the paper clips fall
off.
Activity #2:
Elicit ideas and suggestions from students on how they can make the
nail pick up
more paper clips. Possible ideas are to: 1) use more wire; 2) use more
batteries; 3) use more nails. Break students into groups of four and
let one
group test the idea of using more batteries; another group using 2-3
nails; a
third group using more wire, wrapping the nail 15-20 times; and another
group
wrapping the nail 30-40 times. Reconnect the circuit and pick up as
many nails
as possible. Record the results of each group and discuss results.
Concepts: The strength of an electromagnet can be increased by using
more
batteries and/or more wires. Using more nails will increase the
electromagnet's
capacity to hold more paper clips, without necessarily increasing the
magnetic
force.
Activity #3:
Have students work in pairs. Give each student a 20" length of wire
and a
compass in addition to their battery. Have them secure one end of the
copper
wire to the negative pole of the battery. Have their partner hold the
looped
center of the wire over the compass and they are to observe what
happens to the
compass needle when the other end of the wire makes contact with the
positive
pole of the battery. Repeat this process, but with a slight variation:
attach
the wire to the positive pole of the battery first, then, holding the
looped end
of the wire over the compass, complete the circuit touching the other
end of the
wire to the negative pole of the battery. Observe how the compass
needle
reacts. Discuss observations. Repeat if necessary.
Concept: Electromagnets have poles which can be reversed when the path
of
electricity is reversed. This is not a characteristic of regular
magnets.
Activity #4:
This is a teacher demonstration in which the students will observe what
happens
when iron filings are sprinkled over an electromagnet. Place two
batteries in a
battery holder and connect the end wires to the end wires of an
electromagnet
(nail wrapped with copper wire). Place them on the overhead projector
and place
the clear transparency over the electromagnet. Slowly sprinkle iron
filings
over the transparency and observe what happens to the iron filings.
Discuss
observations.
Concept:
Electromagnets have lines of force.
Assessments:
At the conclusion of the mini-teach, the students will be able to
answer thee
following questions:
Name 3 ways in which magnets and electromagnets are alike.
(Have poles, attract metals, have lines of force)
Name 3 ways electromagnets differ from magnets.
(Electromagnets need electricity to work, the poles of electromagnets
can be
reversed, the strength of electromagnets can be increased)
List 2 ways to increase the strength of electromagnets.
(more batteries, more wire)
References:
Physical Science Activities for Grades 2-8,
Science Curriculum Activities Library
Tolman, Marvin N. and Morton, James O.
Parker Publishing Company, Inc.
West Nyack, NY, 1986
Magnetism and Electricity
Koch, Dallas
Milliken Publishing Co., 1985
Return to Physics Index
Electromagnets
Shirley Porter-Cesair
2004 So. 13th Ave.
Broadview Il 60153
(708) 344-8917
Objective:
Charles R. Henderson
5650 So. Wolcott
Chicago Il 60636
(312) 535-9080
The students will make an electromagnet and determine the strength of
the
electromagnet.
Materials Needed:
Small Compasses
Three feet of insulated copper wire per person
Six-volt battery
Size D batteries
Battery Holders
Pieces of Cardboard
Nails (3 inches or longer)
Paper clips, tacks, pins, or other small magnetic objects
Iron filings
Salad oil
Glass or plastic cylinder (100 ml)
Wrought iron stand
Strategy:
Activity 1
Students will work in pairs. Each pair of students will receive a
baggie
containing materials needed. Allow the students ten or fifteen minutes
to
explore and manipulate the materials. Have one student from each group
connect
their compass with wire through the holes in the cardboard. Insert the
wire
through the Fahnestock clips on both ends. Place the wire over the
compass.
What happens and why?
Concept:
The electrical current flowing through a wire will create a magnetic
field.
This magnetic field causes the needle to turn at a right angle to the
wire.
Reverse the connections to the battery, thus reversing the direction of
the
current flow, and the needle will point in the opposite direction.
Activity 2
Using the same bag of materials, the pairs of students will begin
wrapping the
wire around the nail in the same direction until a foot of wire is left
at both
ends. Insert the end wires into the Fahnstock clips. Hold the
electromagnet
over a small pile of paper clips, tacks or other small metal objects.
How many
objects does your electromagnet attract? Take the wire off the battery
terminal, and the tacks will immediately fall off.
Concept:
The current passing through the wire produces an invisible magnetic
field. When
the current is cut off, the magnetic field disappears, then the
molecules of
the iron return to their helter-skelter position and the nail loses
most, but
not all, of its magnetism.
Performance Assessment:
As a result of the electromagnet mini-teach, the sixth grade students
will be
able to describe the characteristics of a magnet and an electromagnet.
Both
attract metal and have magnetic fields; the electromagnet needs an
electrical
current.
The students will be able to make an electromagnet with a wire, a
battery, and
a nail.
The students will be able to test the strength of the electromagnet by
using
more coiled wire and additional batteries and nails.
Conclusions:
In activity 1 we found that electricity can produce magnetism and
magnetism can
produce electricity. The opposite ends or poles of magnets are
attracted to
each other and like ends repel.
In activity 2 we found that current through a wire produces an
invisible
magnetic field. When the current is cut off, the magnetic field
disappears,
then the molecules of the iron return to their helter-skelter position
and the
piece loses most, but not all, of its magnetism.
References:
Safe and Simple Electrical Experiments. Rudolf F. Graf.
Publications,
Inc.,N.Y., 1964. pps. 86-88 and 93-94.
Be a Kid Physicist. William R. Wellnitz, Ph.D.,
Hill, Inc.,
Blue Ridge Summit, PA. 1993. p, 82.
Dover
Tab Books.
McGraw-
Science Projects About Electricity and Magnets.
Enslow
Publishers, Inc., N.J., 1994. pps. 72-82.
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Robert Gardner.