# Build an Electromagnet

Urban and Civil

Nov 16, 2013 (4 years and 5 months ago)

115 views

Build an Electromagnet

Purpose

To learn how to construct and use an electromagnet. To learn that electromagnets are temporary
magnets and work only when electricity passes through the coil of wire.

Context

People use the power of magnets in many ways. Magnetism and electricity are closely related. In
an electric generator, an electric current is set up in a coil of wire that moves through a magnetic
field. An electric current moving through a wire coil wrapp
ed around an iron core produces
magnetism. The close interrelationship between magnetism and electricity has many
applications.

By exploring magnets, students are indirectly introduced to the idea that there are forces that
occur on earth which cannot be

seen. This idea can then be developed into an understanding that
objects, such as the earth or electrically charged objects, can pull on other objects. It is important
that students get a sense of electric and magnetic force fields (as well as of gravity)

and of some
simple relations between magnetic and electric currents. (
Benchmarks for Science Literacy
,
p.
93
4
.) This lesson continues the exploration of magnetism beg
un in Science NetLinks lessons
Magnets 1: Magnetic Pickups
5
,
Magnets
2: How Strong is Your Magnet?
6
, and
Exploring
Magnetic Fields
7
. Before doing this activity, students should have built simple electric circuits
with batteries and flashlight

bulbs.

In this lesson, students will make a simple electromagnet by wrapping a wire around a nail and
attaching the ends of the wire to a battery to make an electric circuit. As current flows through
the coil, a magnetic field is produced and the nail i
s magnetized. Lessons such as this help to
build a foundation upon which students can develop their ideas about gravitational force and how
electric currents and magnets can exert a force as well.

Planning Ahead

Materials:

Electromagnets
8

student E
-
Sheet

Build an Electromagnet
9

student sheet

To build the electromagnet, you will need:

Wir
e cutter

22
-
gauge insulated wire, cut into 24” long strips

Per Group:

3” long iron or steel bolt

24" long 22
-
gauge insulated wire strip

2 D
-
cell batteries

2
-
3 alligator clips or tape

20 paper clips & other magnetic objects

Scissors to strip the wir
e

Motivation

Begin with a brief discussion in which students can review concepts about magnetism, using
questions such as these:

What is a magnet?

What is a magnetic field?

Can you make a magnet?

If students' responses indicate that they need to review magnetism, you can refer them to
A
Regular Magnet
10

for a brief refresher.

Then say to students, “Electromagnets are temporary magnet
s that let us turn magnetic fields on
and off so we can control the magnetic energy.” Then ask students to speculate on why it is
advantageous to turn the fields on and off. Tell students that they will conduct an activity to
explore how electromagnetic fi
elds work.

Development

Pass out the
Build an Electromagnet
9

student sheet and have students do the activity in pairs.
Students will build an electromagnet and test its strength. To save time, you can pre
-
strip the
ends of the wire for each pair of students. You can use a wire stripper, scissors, or a sharp knife
t
o remove the insulation.

Before students begin to work on their own, make sure that each group has the needed materials
to build their electromagnet. To help students, you can ask questions such as the following
before they begin:

Do you think an electr
omagnet will be attracted to the same things as a regular magnet?

Will it be attracted to all metal things?

Will it be attracted to other magnets?

As students are building the electromagnet, walk around the class to make sure that they are on
track. Ask

questions such as:

What happens to the electromagnet if you disconnect one of the wires from the battery?

How many turns of the wire does it take to pick up a paper clip?

Are more turns better?

After students have built their electromagnet and tested
it, you could ask questions such as the
following to extend their ideas:

What happens if you build another electromagnet using a different size battery?

How many paper clips will this new electromagnet pick up?

Does using a different size battery (“A” versus “C”) make a difference?

What things are attracted to a permanent magnet, such as a refrigerator magnet? Are
these the same things that are attracted to the electromagnet?

Are there any differences between w
hat the permanent magnet and the electromagnet can
do?

After students have completed the activity, discuss the questions on their student sheets:

What is traveling through the wires? Where does the electricity come from?

Is an electromagnet a temporary
magnet or a permanent magnet? Why is it a temporary
magnet?

How can you measure the strength of your electromagnet? How can you make your
electromagnet stronger?

Do not dismantle the electromagnets until you are finished with electromagnet activities, bu
t be
sure they are disconnected from the batteries at the end of your class.

When you are finished with electromagnet activities, unwrap the wires and be sure the
electromagnets are not connected to the batteries. Students can label their electromagnets
with
tape and use them over and over.

Next, using the
Electromagnets
8

student E
-
Sheet, students will explore
Using Electromagnets
11
.
After students have explored the site, review how electromagnets are used in each of these items:

speaker

electric bell

relay

electric motor

Assessment

To assess student understanding, instruct your students to write several paragraphs to summarize
some of the uses of electromagnets described in the Web resource. They should explain the
function of the electromagnet in the devices described. They also sho
uld discuss how the
electromagnets in those devices are like the ones they built.

After doing the activity and exploring the website, students should understand that when an
electric current flows through a wire, a magnetic field is produced around it. T
his concentrates
the magnetic field, especially if we put an iron bar in the center of the field. They also should
generally understand that there are two ways to increase the strength of an electromagnet. One is
by adding more length to the wire (more coi
ls). The other is by increasing the amount of
electricity going through the wire. By increasing these two things, engineers have developed
very powerful electromagnets such as the enormous ones used in junkyards to lift large piles of
metal.

Extensions

More detailed information about magnets and electromagnets can be found at
Magnetic Fields
12

or
Magnetics
Tutorial
13
.

More activities to try with electromagnets can be found at
How Electromagnets Work:
Experiments to Try
14
. Also from How Stuff Works, students can learn how to
Make an Electric
Motor
15
.

Created :06/10/2005

© Copyright AAAS 2006. All rights reserved.

Links

1.

http://sciencenetlinks.net/benchmark_sub.php?BenchmarkID=4&Grade=6
-
8#7

2.

http://www.sciencenetlinks.com/resources_individual.cfm?DocID=116&Grade=6
-
8&Benchmark=4

3.

http://www.sciencenetlinks.com/resources_individual.cfm?DocID=382&Grade=6
-
8&Benchmark=4

4.

http://ww
w.project2061.org/tools/benchol/ch4/ch4.htm#ForcesOfNature

5.

http://www.sciencenetlinks.com/lessons.cfm?Grade=3
-
5&BenchmarkID=4&DocID=175

6.

http://www.sciencenetlinks.com/lessons.cfm?Grade=3
-
5&BenchmarkID=4&DocID=159

7.

http://www.sciencenetlinks.com/lessons.cfm?
BenchmarkID=4&DocID=266

8.

http://www.sciencenetlinks.com/Esheet.cfm?DocID=125

9.

http://www.sciencenetlinks.com/pdfs/build_actsheet.pdf

10.

http://www.howstuffworks.com/electromagnet1.htm

11.

http://www.nelsonthornes.com/secondary/science/scinet/scinet/electric/magnets
/uses.htm

12.

http://www
-
spof.gsfc.nasa.gov/Education/wmfield.html

13.

http://www.ocean.washington.edu/people/grads/mpruis/magnetics/

14.

http://science.howstuffworks.com/electromagnet3.htm

15.

http://www.howstuffworks.com/framed.htm?parent=electromagnet.htm&url=http://ww
w.
eas.asu.edu/~holbert/wise/electromagnetism.htm