Summary:

Magnetic Muscle; is set of quantitative guided inquiry activities where you will use
a number of techniques to characterize the strength of magnets.

Learning Goals / Objectives:

1.) Students will gain a hands on understanding of many properties of permanent magnets. In particular they will learn

• About magnetic poles and their interactions with each other
• How to visualize and measure magnetic fields
• What materials are magnetic and what materials are not magnetic
• How to characterize the field strength of a permanent magnet

Background

Anticipatory Set:

Driving Questions
1.) How do magnets work?
2.) How does a compass work?
3.) How can we “see” magnetic fields?

Instructions / Activities:

In this series of activities we are going to quantify the strength of our magnets using:

• Attraction (Magnet balance made from blocks and a ruler and A hanging magnetic basket.)
• Repulsion (Floating magnet set.)

Block Scale
Make sure you have access to the following:

• A few magnets to test. (One should be a ring magnet from the floating magnet set.)
• Blocks
• Ruler with cup
• Washers of various sizes
•  Paper tape
• Cardboard spacers
• Paper clips
• Velcro

A. Direct contact:
1.) Construct a block balance using blocks and a ruler with a cup (sample depicted above). Note, the ruler has a piece of magnetic metal attached to its underside (the opposite end from the cup). Before moving on, prove to yourself that the metal will attach itself to one of your test magnets.

2.) Use Velcro or paper tape to attach a “test” magnet to your magnet stand.

3.) Carefully add washers to the cup until the metal detaches itself from the magnet. Record the number and type of washers required to detach the metal.

4.) Repeat this measurement with the same test magnet a few times. Is the measurement reproducible? What tweaks need to be made to make it more reproducible? Record your measurements in your notebook.

5.) Repeat for each of your test magnets. Test 4 magnets 2 times each. It may be interesting to have at least 2 of the 4 test magnets be identical. Record your measurements in your notebook.

Follow up questions:
1.) Which magnet is the strongest? The weakest?
2.) Any surprises?
3.) How robust do you think this measurement technique is?

B. With spacers:
1.) Pick your strongest test magnet.

2.) Re-measure the number of washers required to detach the metal from the magnet.

3.) Place a cardboard spacer above your test magnet, and repeat the measurement. Will it take fewer or more washers to detach the metal from the magnet? Record your observations.

4.) Repeat measurement with a second, third, etc spacer until the metal is no longer held by the test magnet. Note: you may need to readjust the height of the test magnet stand and/or the block balance to accommodate the height of the spacers.

Follow up questions:

1.) Can you make a general rule about the strength of a magnet as a function of distance?

2.) Were the changes you saw linear? (you may want to think about a graph for this).

3.) Any surprises?

4.) How robust do you think this measurement technique is?

Gondola Hanger
Make sure you have access to the following:
• A few magnets to test
• Stand
• Cup with string
• Washers of various sizes
• Cardboard spacers
• Paper clips

1.) Pick a few (~4) test magnets.

2.) Construct a gondola hanger with one of the test magnets. Two potential configurations above.

• In configuration A, the cup is directly attached to the stand, the test magnet is in the cup, and washers will hang from the paperclip below the magnet.
• In configuration B, the magnet is directly attached to the stand, the paperclip below the magnet is attached to the cup and washers can be placed in the cup.

3.) Carefully add washers to the clip or cup until the clip detaches itself from the magnet. Record the number and type of washers required to detach the metal.

4.) Repeat this measurement with the same test magnet a few times. Is the measurement reproducible? What tweaks need to be made to make it more reproducible? Record your measurements in your notebook.

5.) Repeat for each of your test magnets. Test 4 magnets 2 times each. It may be interesting to have at least 2 of the 4 test magnets be identical. Record your measurements in your notebook.

Follow up questions:
1.) Which magnet is the strongest? The weakest?
2.) Any surprises?
3.) How robust do you think this measurement technique is?

Hoverer
Make sure you have access to the following:
• Floating Magnet Set
• Ceramic ring magnets (if you have one).
• Washers of various sizes
• Ruler

In this activity we will estimate the strength of the magnetic field using repulsion.

1.) Start with your floating magnet set. Place two ring magnets on the floating magnet stand with their North poles facing each other (see diagram above). What do you see?

2.) Measure the distance between the two magnets.

3.) Place a washer on top of the upper most magnet. Record the height.

4.) Repeat, adding one washer at a time and recording the height until the magnets touch.

5.) Take the washers off and repeat the experiment with the South poles facing each other. Did you obtain a similar result? Are your results reproducible?

Follow up questions:
1.) How does this data compare to the spacer data you collected using the block scale?
2.) Any surprises?
3.) How robust do you think this measurement technique is?

 

Assessment:

Teacher’s Discretion

Wrap-up / Closure:

General follow up questions for Magnetic Muscles
1.) Which technique for estimating magnetic field was:

• Most robust?
• Most reproducible?
• Most quantifiable?

Justify your answers.

2.) From your data, can you think of a common unit you might Use to describe field strength? Explain.

Attachments:

These materials are contained in a kit in our Library!