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Magnetic Field Viewing Bottle
- William BeatyWhen you expose small steel fibers to a very strong magnetic field, they will align with the field, making it visible. You can demonstrate this phenomenon with this easy-to-make viewing bottle.
______
|| ||
||____||
___----- -----___
/ | \
| _ \ |
| --__ \ |
| \ \ |
| - \ |
| __ ---___ | ________________
| __ | - 1/2"-1" - / \ MAGNET
| ___-- --- | space \________________/
| __-- / |
| _ / |
| / / |
| / |
| | | | The floating fibers make the
| | | magnetic field visible
\__________________/
BOTTLE
Materials:
- bar magnet*
- extra-fine steel wool** (type 000 or 0000) from a hardware store
- plastic bottle full of baby oil with paper label on only one side, or a removable label if on both sides
- scissors
Optional:
- rubbing alcohol to remove label
- pan or shallow dish for the alcohol
- white spray-paint (optional)
*If you have difficulty finding a bar magnet, try Radio Shack stores. They sell small disk magnets, which can be stacked up to form bar magnets. A few dollars' worth of their 1-inch "donut" disk magnets is enough to make several big stacks that you can also use in future science projects.
**Steel wool looks like a rolled-up wad of grey hair, NOT the coppery coarse net used for scrubbing dishes. Any grade of steel wool will work, but extra-fine wool will settle more slowly, so you won't have to shake the bottle so often.
Don't forget: Keep magnets away from credit cards, computer disks and videotapes to avoid damage to these items. Also keep them away from color TV and computer screens, since they can create permanent color blotches, which can only be removed with specialized tools.
Procedure
Remove the Label
- If your oil bottle has labels on both sides, peel the label from one side by picking at it with your fingernails while running it under warm water.
- An easier way to remove the label is to soak one side of the bottle in a shallow dish of rubbing alcohol for about 10 or 15 minutes, and then peel the label off.
- Use a bit of alcohol and a paper towel to clean off the remaining glue.
- You can improve your bottle by removing all labels and painting one side of the bottle with white spray paint. This gives you a smooth white background against which to view the floating dark fibers.
Make the Steel Fibers
- Find one end of the steel-wool roll, and partially unroll it.
- Use the scissors to trim the wool straight across to remove the frayed fibers, then repeatedly cut across the wool to make many very narrow strips.
- Cut strips narrower than 1/8", as small as 1/16" if you can. This will give you thousands of short steel fibers.
- Use a teaspoon to measure how much you have cut, being careful not to pack the fibers down excessively.
- You will need a heaping teaspoon of fibers, or about one square inch of unrolled steel wool. If you use a really tiny bottle of baby oil, use less than a teaspoon of fibers.
Note: If you use too many fibers, the fibers will clump and settle to the bottom of the bottle too fast. If you use too few, the fibers will be difficult to see.
Mix the Fibers into the Oil
- Gently wad up the fibers.
- Drop the wad into the bottle of baby oil.
Experiment with Your 3D Magnetic Field Viewer
- Hint: It helps to hold the bottle in bright light so you can see the tiny fibers against the white label or paint on the back of the clear bottle.
- Cap the bottle securely and shake it until the wad of fibers is spread evenly throughout the oil.
Note: It's best to shake the bottle with a violent rotating wrist motion rather than just shaking straight up and down. Up-and-down shaking only works if there is a large bubble. - While the fibers are still mixed into the oil, hold your magnet sideways (as shown above) about 1/2" to 1" away from one side of the bottle. You'll see the tiny fibers align themselves and reveal the three-dimensional magnetic field pattern.
Note: If the fibers clump against the magnet, then you are holding the magnet too close to the bottle. - As the fibers start to settle to the bottom (every 10 or 15 seconds), shake the bottle to continue experimenting.
Different things to try (see diagrams below)
- Hold the magnet up and down.
- Hold the same magnet pole near each side of the bottle; i.e., an "N" pole facing an "N" pole (the poles that repel each other).
- Hold opposite magnet poles near each side of the bottle; i.e., an "N" pole facing an "S" pole (the poles which attract).
______
|| ||
||____||
___----- -----___
/ \
| |
| |
| | __
| | / \
| | | |
| What will | | |
| you see? | | |
| | - 1/2"-1" - | |
| | space | |
| | | |
| | | |
| | \__/
| | MAGNET
| |
| |
\__________________/
BOTTLE
______ || || ||____|| ___----- -----___ / \ | | | | | | | | S N | | N S ____________ | What will | _____________ / \ | you see? | / \ \____________/ | | \_____________/ MAGNET | | MAGNET | | Also try turning this | | magnet so the "S" pole | | faces the "N" pole | | on the other magnet \__________________/ BOTTLE
Used by permission of Bill Beaty.
For more field-viewing fun, try the 3D Electric Field Viewing Bottle project.
Be sure to check out our Science Fair Project Books and Kits too. You'll find plenty of exciting projects and ideas for budding young scientists.
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