Electromagnitism Applications
NASA’s Mini AERCam
Lesson Plan
Subject:
Physics
Author:
Objective: Describe the relationship between magnetism and electricity
Introduction:
A strong field can be produced if an insulated wire is wrapped around a soft iron
core and a current passed through the wire. The strength of the magnetic field
produced by such an electromagnet depends on the number of coils of wire, the
magnitude of the current, and the magnetic permeability of the core material; a
strong field can be produced from a small current if a large number of turns of wire
are used. Unlike the materials from which permanent magnets are made, the soft
iron in the core of an electromagnet retains little of the magnetism induced in it by
the current after the current has been turned off. Electromagnets are used to lift
large masses of magnetic materials, such as scrap iron. They are essential to the
design of the electric generator and electric motor and are also employed in
doorbells, circuit breakers, television receivers, loudspeakers, atomic particle
accelerators,
and
electromagnetic
brakes
and
clutches.
Electromagnetic propulsion systems can provide motive power for spacecraft.
Electromagnets are also essential to magnetic levitation systems.
NASA has developed a free-floating camera that will be used by astronauts in
space. The camera will allow the astronauts 'extra eyes' that they can use while
working on and/or making repairs to the International Space Station (ISS). They
need a way to attach the camera to the ISS so that it can have a place to remain
when not in use. The teacher should elicit ideas from the students to solve this
problem, and then ask them to think in terms of electricity and magnetism. The
teacher should then show the MIni-AERCam Power Point presentation. During
the slide show the teacher will clarify terminology and field questions from
students (see notes pages of slides for clarification). The teacher will then
introduce the lab activity and ask the students how what they are about to do is
related to the work that the researchers at the Spacecraft Technology Center in
College Station, TX.
Concept Development:
Students will conduct the Vernier Physical Science with Calculators-Electromagnets: Winding Things Up using the TI-83 Graphing calculator and a
magnetic field sensor.
 Pre-Lab
1. Demagnetize the iron nails beforehand by striking them on something
firm, such as a ring stand base.
2. Use rubber or plastic-covered copper wire 22 or 24 gauge. This is
sometimes called bell wire. Cut the wire in 80-cm lengths and remove
about 1 cm of covering at each end. Single strand wire works best.
3. For good results, the batteries must have a strong charge before this
experiment. We suggest that you test all batteries using a 21-wind nail
prior to use, and reject those giving less than a 1.5-mT reading.
4. Be sure to tape sensors to table top as they are breakable.
 Lab
o Have students experiment with the placement of the magnetic source
prior to the lab experiment. You may use regular magnets and/or the
electromagnets. Students should notice that the magnetic field
readings approach zero as the magnet is placed parallel to the detector.
As the magnet is moved around the detector, the readings will
increase and max out when the magnet is exactly perpendicular to the
detector. The readings will be negative if placed perpendicular on the
opposite side. Emphasize the importance of consistent magnet
placement perpendicular to the detector through the course of the
experiment.
 Post-Lab
o A direct relationship exists between the number of winds and the
magnetic field strength. The graph of magnetic field vs. number of
coils is linear.
o The students can predict the magnetic field strength for various
numbers of winds by interpolating from the graph or by multiplying
the slope by the number of coils. Students could perform an
experiment to confirm their predictions.
 Ask students the following:
o What might happen if a battery of a higher voltage was used?
 You may choose to demonstrate the difference or allow
students to investigate if time permits.
 Increased voltage results in increased magnetic strength.
o What might happen if a different core material was used for the
electromagnet?
 Student could also investigate the effects of different
electromagnetic cores including plastic (pen tube) or aluminum
(rolled-up foil).
 Core must be a good conductor of electricity.
o What might happen if the docking station on the ISS used too much
electricity to attract the Mini-AER Cam?
 Too much electricity could lead to a ‘wreck.’
o What might happen to the Mini AERCam if the ISS were to lose
power?
 Loss of power could result in the loss of the Mini-AERCam as
it would no longer be magnetically attracted to the ISS.
Student Practice:
 Day One:
o Electromagnets—Winding
Things
Up
(Instruction-driven
investigation)
 Determine how electromagnetic field strength varies with
number of coils around an iron nail.
 Day Two:
o Electromagnetism-- Design Your Own Lab
(Inquiry-based
investigation)
 Design an experiment to determine quantitatively how the
electromagnetic field strength varies with distance using the
following equipment: electromagnetic field sensor, centimeter
ruler, iron nail, insulated copper wire, a D-cell battery.
Assessment:
 Lab write-ups are checked for accuracy.
 Design your own lab write-up graded with rubric.
o Be sure to present students with rubric prior to assignment.
 Performance assessment could be used for laboratory technique.
Closure:
 Day One Exit Ticket:
o How does the number of coils affect the magnetic field of an
electromagnet?
o What application does NASA have planned for electromagnets on the
international space station?
 Day Two Exit Ticket:
o What is the relationship between magnetic field strength and distance?
o How does the space environment complicate experimental design for
engineers?
Notes to Teacher:
Run through lab exercise with Vernier equipment prior to student use.
Resources:
Mini-AERCam :
http://aercam.jsc.nasa.gov/index.htm
previous AERCam Sprint that flew in 1997:
http://vesuvius.jsc.nasa.gov/er_er/html/sprint/index.htm
Vernier Lab:
http://www2.vernier.com/sample_labs/calculator/physical_science/electromagnets.pdf
NASA--Building a Droid for the ISS:
http://science.nasa.gov/headlines/y2001/ast23jul_1.htm
Electromagnet Information:
http://science.howstuffworks.com/electromagnet.htm
Elementary Electromagnets
http://www.lbl.gov/MicroWorlds/teachers/movingelectrons.pdf
Additional activity—Inverse Cube Law of Magnetic Forces
http://image.gsfc.nasa.gov/poetry/activity/l23.pdf