ferromagnetic fluid: Liquid that get attracted to magnet!
This activity will help you to learn about magnetism in a fun way.
What you need:
1) Laser printer toner
2) Neodymium magnet
3) cooking oil (vegetable oil)
4) Mixing bowl and stick
5) Balloon
6) glass plate
7) A bottle filled with water (3/4)
Instructions:
1) Pour the toner into the mixing bowl and add a small amount of vegetable oil. Stir up the mixture with the stick. The oil should be added carefully to get the correct concentration for your solution that should not be too diluted. Your ferromagnetic fluid is now ready and it's time to do some tricks :)
2) Pour some of the mixture into the glass plate. Place the Neodymium magnet beneath the plate and move it around. Your fluid will move as you move the magnet. It follows the magnetic field created by the magnet.
3) You can also move your magnet directly above the fluid and collect some of it on your magnet. However, if you do not want it on your magnet, place the magnet into a balloon and swirl it above your fluid. The mixture will get attracted to the magnet inside the balloon and some of it will stick to the outside of the balloon. To remove what got stuck to the balloon, just remove the magnet from the balloon and collect the mixture back into the plate.
4) Pour a small amount of your fluid into a bottle filled with water (3/4), put the lid back on the bottle and bring your magnet close to it. You will observe how your fluid still follows the motion of the Neodymium magnet.
Explanation:
The toner powder used in laser printers contains ferromagnetic nanoparticles (fine iron oxide dust). These particles are responsible for making the mixture (toner powder + oil) ferromagnetic and cause it to get attracted to the Neodymium magnet.
Check this youtube video for visualization
http://www.youtube.com/watch?v=sYEhOjCWp-k