Tap, Tap, Reveal! The Mysterious Patterns of Magnetic Field Lines (Observing Magnetic Fields)
I’m Ken Kuwako, a Science Trainer. Every day is an experiment.
The “magnetic field” that forms around magnets and electric currents is an invisible concept, which can make it difficult for students to visualize. In class, I explain things like, “Magnetic field lines run from the north pole to the south pole,” and “The direction of a magnetic field is the direction in which the north pole of a compass points.” But I often feel that it is hard to completely clear up the students’ feeling of, “I kind of get it, but what is actually happening?”
I had assumed that students had already experienced an experiment using iron filings to visualize magnetic fields in elementary school. Apparently, that’s not the case. They may have collected iron filings in elementary school, but they haven’t actually used them to explore magnetic fields.
In that case, we definitely need to make sure they get a proper hands-on experience with it!
When using iron filings
Science Recipe: What You’ll Need
- Magnets: Prepare several types, such as bar magnets and horseshoe magnets. This allows students to observe a variety of magnetic field patterns.
- Clear plastic file folder
- Compass: Used to check the direction of the magnetic field. Having several compasses available for each group makes the activity more efficient.
- Magnetic chips: You can use commercially available iron filings or similar materials from a hardware store. However, iron filings can be dangerous if they get into the eyes, so I recommend using Mag Chips instead. They are easy to reuse, too!
Experiment Procedure (Including Tips for Giving Instructions to Students!)
Take a look at the video below.
1. Place the magnet on the desk.
2. Put the magnet inside the clear plastic file folder. This is the key point!
3. Sprinkle the Mag Chips over it like you’re seasoning food with pepper.
4. Gently tap the clear file folder.
5. Use a compass to check the direction of the magnetic field.
6. Return the Mag Chips to their container or another suitable case.
Through this experiment, students can visually see the presence of an invisible “magnetic field” and get a real feel for its properties.
With a bar magnet, you should see curved lines running from the north pole to the south pole. When two north poles are brought close together, you should see curved patterns that bend away from each other, reflecting their mutual repulsion. This helps students understand that magnetic field lines represent not only the shape of a magnetic field but also its direction, and that the magnetic force is stronger where the field lines are more densely packed, such as near the magnetic poles.
Just as when two north poles are brought close together, students can observe how the magnetic fields of multiple magnets interact with one another, producing a combined magnetic field pattern.
This suggests that magnetic fields do not exist in isolation. Instead, they can overlap and combine with other magnetic fields, helping students develop a deeper understanding of how magnetic fields work.
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