Magneto Hydro Dynamics Demonstration




Introduction: Magneto Hydro Dynamics Demonstration

About: I'm a total gearhead. I love working on cars, airplanes, rockets, sailboats, whatever. Cars i've owned and/or rebuilt: 1966 Pontiac Grand Prix, 1977 Lotus Esprit, 1979 Fiat X1/9 & Strada, 1970 Ford Bronco...

With a few readily available household items anyone can create this experiment in 5 - 10 minutes, demonstrating magneto hydro dynamics.  Basically, when electricity moves through a conductive fluid in a magnetic field, a force, called the Lorentz Force, is imparted on the fluid, causing it to move.
More can be read about it here:

Step 1: Household Materials

1 small circular magnet (can be purchased cheap at any hardware store)
1 small white cap
2 nails
1 9 volt battery

Step 2: Mix a Dash of Salt Into Some Water

Water is not a very good conductor of electricity so we'll need to add some salt to make it conductive.
Fill up the white cap with water and mix in a pinch of salt.

Step 3: Lightly Sprinkle Some Pepper Onto the Saltwater Mix

 The pepper is used for visualizing the circular motion of the water. 

Step 4: Place the Cap With the Saltwater/pepper Mixture on the Magnet

The water will flow clockwise or counterclockwise depending on the orientation of the magnet.   Feel free to flip the magnet and watch the water switch directions. 

Step 5: Attach a Small Nail to the Battery

The 9 volt battery was perfect for holding in one of the nails.  You can tape or hold with your fingers the other nail against the other battery connector (terminal).

Step 6: Insert One Nail Into Center of Cap and the Other on the Outside Rim

You will see the pepper start flowing around the center nail.   Basically when electricity flows thru a conductive fluid in a magnetic field, a force is imparted on the fluid making it spin.  

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    6 Discussions


    I followed the instructions, but didn't get any results other than splitting the water molecules.


    Reply 10 years ago on Introduction

    Did u put enough salt in the water? Was your magnet strong enough? Sounds like your battery had juice since u were seeing some electrolysis. There are alot of good examples at


    10 years ago on Introduction

    Your next challenge is to build a silent submarine...


    Reply 10 years ago on Introduction

    Just make sure it doesn't sound like magma displacement.  ;)