Mapping a Magnetic Field*

Teacher Version(.doc)

Student Version(.doc)

• Grade Level(s):  6th, 7th, and 8th
• Primary Focus: Science; NC Standard Course of Study Areas: 6th: 5.03; 8th: 4.04
  • (Key Concepts:  Magnetic fields and poles)
• Secondary Focus: Math; NC Standard Course of Study Areas: 6th: 1.01, 1.07, 5.04; 7th:4.01; 8th: 1.02, 4.01
  • (Key Concepts:  Rational numbers and graphical analysis)
• Computer/Technology Skills: Calculators, Probeware, Data Visualization; NC Standard Course of Study Areas: 6th: 3.01, 3.03, 3.06; 7th: 1.10, 3.01, 3.02; 8th: 2.06, 3.01
• Essential Question: How do magnets work? Why do you feel a magnet pull towards a metal object or another magnet when they are close together but not when they are far away?
• Summary of Activity: Students will create a magnetic field using a bar magnet ad then measure the strength of that field at increasing intervals using a Magnetic Field Sensor.
• Cognitive Teaching Strategies: Students will make predictions as to the effect of distance on the strength of the magnetic field. With this information, students will determine how the magnetic field changes and possibly the shape of the field.  It may help students to visualize the magnetic field by placing a white piece of paper with a sprinkling of iron fillings over a bar magnet.  
• Materials:
  • TI-83 Plus or TI-84 Plus graphing calculator
  • EasyData application
  • EasyLink data-collection interface
  • Vernier Magnetic Field Sensor
  • bar magnet
  • clear tape
  • ruler 
  

Procedure:

Figure 1

1. Using clear tape, tape a ruler to your desktop. Place a bar magnet beside the ruler. Position the S-pole end of the magnet at the 3 cm mark as shown in Figure 1. Tape the magnet to the tabletop.
2. Set up the Magnetic Field Sensor.
   1. Turn on the calculator.
   2. Set the Magnetic Field Sensor on the Low position.
   3. Connect the Magnetic Field Sensor, data-collection interface, and calculator.
3. Set up EasyData for data collection.
   1. Start the EasyData application, if it is not already running.
   2. Select  from the Main screen, and then select New to reset the application.
   3. Select  from the Main screen, and then select Events with Entry.
4. Zero the Magnetic Field Sensor. 
   1. Make sure the Magnetic Field Sensor is far away from the bar magnet.
   2. Hold the sensor so the white spot faces up and is parallel to the tabletop.
   3. Select  from the Main screen, and then select Zero…
   4. Select  to zero the Magnetic Field Sensor.
5. Select  to begin data collection.
6. Collect data at the 0 cm distance. 
   1. Place the Magnetic Field Sensor perpendicular to the bar magnet as shown in Figure 1. Center the white spot at the 0 cm mark of the ruler. Rotate the Magnetic Field Sensor so the white spot faces up and is parallel to the tabletop. Keep the white spot parallel to the tabletop throughout the experiment. When the reading has stabilized, select .
   2. Type 0 (for 0 cm) and select .
7. Move the sensor, and repeat the Step-6 procedure at 1 cm intervals until you have reached a point 3 cm beyond the N-pole end of the bar magnet.
8. Select  to end data collection.
9. Record the magnetic field strength values.
   1. When data collection ends, a graph of magnetic field strength vs. distance will be displayed. Use  to examine data points along the curve. As you move the cursor right or left, the distance (X) and magnetic field strength (Y) values of each data point are displayed above the graph.
   2. Record the magnetic field strength values.
10. Sketch or print the graph as directed by your teacher.

Instructional Strategies:

Magnetic fields are a very difficult concept for students because they cannot see them.  It may be helpful to first discuss other concepts that relate to “invisible” phenomena.  Friction, force, even electricity are things that students can see the effects of but are “invisble”.

Additional Resources for this lesson:

The “HowStuffWorks” website has great information on magnets and magnetic fields.  www.howstuffworks.com

Re-Teaching and Enrichment Strategies:

Introduce students to electromagnets.  Take a nail, wrap a copper wire around the nail multiple times and then connect the wires to a battery.  Have students discuss the differences between magnets and electromagnets.

Data Collection and Analysis:

HYPOTHESIS:

DATA:

Distance (cm)	Magnetic field (mT)	Distance (cm)	Magnetic field (mT)	Distance (cm)	Magnetic field (mT)
0		9		18
1		10		19
2		11		20
3		12		21
4		13		22
5		14		23
6		15		24
7		16		25
8		17		26

QUESTIONS:

1. Where on the bar magnet was the largest positive magnetic field strength reading observed? 
2. Where on the bar magnet was the most negative magnetic field strength reading observed? 
3. At what centimeter distance does your graph have a zero value magnetic field strength value? At what point is this on the bar magnet? 
4. Why does the graph have both positive and negative magnetic field strength values? 

Extension:

1. Test the strengths of different magnet types at the same distance from the sensor. Which magnet types are strongest? Weakest? 

DISCUSSION:

How do magnets work? Why do you feel a magnet pull towards a metal object or another magnet when they are close together but not when they are far away?

 

*Adapted from: Volz, D., & Sapatka, S. (2000). Middle School Science with Calculators. Beaverton, OR: Vernier Software & Technology. s