demonstrations:diamagnetism_of_water
Diamagnetism of Water
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required
Categories: Magnetism
Alternative titles: Water and Magnetic Repulsion
Summary
Water is diamagnetic, meaning it creates a weak magnetic field opposite to an applied external magnetic field. This property can be demonstrated by the slight repulsion of water from a strong magnet.
Procedure
- Fill a glass with water and place it on a stable surface.
- Bring a very strong magnet (e.g., 12,200 gauss or stronger) close to the side of the glass.
- Observe carefully as the water is very weakly repelled, causing a small but detectable effect. Reflecting grid paper from the surface of the water can help to show this.
- Discuss how the induced magnetic field in the water opposes the applied field.
- Extend discussion to stronger field demonstrations: with magnetic fields greater than 10 Tesla, even small animals (like frogs) can levitate because their bodies are mostly water (lookup videos of this).
Links
REPELLING WATER - ENGLISH - Water is diagmatic and can be repelled by a magnet - Arvind Gupta:
Diamagnetism of Water - Ludic Science:
📄 The diamagnetism of water - auris: https://www.aurismagnetic.com/en/content/52-the-diamagnetism-of-water
Variations
- Try the experiment with other diamagnetic materials such as copper, zinc, bismuth, or glass and compare effects.
- Test paramagnetic materials (like aluminum) to observe how their behavior differs from diamagnetism.
- Use superconductors to demonstrate stronger diamagnetic levitation effects (the Meissner effect).
- Compare weak water repulsion with ferromagnetic attraction for contrast.
Safety Precautions
- Handle very strong magnets with care to avoid pinching injuries.
- Keep magnets away from electronic devices, bank cards, and medical implants.
- Do not attempt living-animal levitation demonstrations in a classroom, as they require extremely powerful magnets (over 10 Tesla) and specialized facilities.
Questions to Consider
- Why does water repel from a magnet instead of being attracted? (Because water is diamagnetic, it induces an opposing magnetic field.)
- Why is the effect so weak in everyday experiments? (Diamagnetism in water is very weak compared to ferromagnetism, requiring very strong fields to see noticeable effects.)
- Why can frogs be levitated in extremely strong magnetic fields? (Their bodies are mostly water, and the induced diamagnetism opposes gravity when the magnetic field is strong enough.)
- Why can’t we levitate humans with classroom magnets? (The required magnetic fields—tens of Tesla—are far beyond the strength of ordinary magnets and would need large laboratory setups.)
- How does diamagnetism differ from ferromagnetism? (Diamagnetism produces a weak repulsion in all materials, while ferromagnetism produces strong attraction in certain materials like iron, cobalt, and nickel.)