Here is how to build a simple little boat that moves through salt water at a snails pace via MHD propulsion.
The craft is not designed for performance; it’s designed to demonstrate a functional MHD craft made with inexpensive, easily available materials. While it may move slowly, hey, it moves, and you can make it in about five minutes.
9V batteries. Plural, because they will get used up very quickly. Rechargables would be nice.
Two quarters (or similar coins)
Two short cables with alligator clips on the ends
A sturdy foam tray, like the kind that meat or vegetables are sometimes packed in
a strong neodymium magnet (I suggest one about an inch in diameter by half an inch thick)
Regular transparent tape.
Tools: a small knife.
Optional: Double-sided tape.
Since your vehicle requires salt water to run, you will also need to provide that. Grab some salt, water, and a nonmagnetic basin that’s at least several times as wide as your craft. A plastic storage bin or kiddie pool works well. If your bathtub is nonmagnetic (check it!) you can use that. While the craft could (in principle) run in the ocean, wind and water currents will make it hard to see the small propulsion effect.
First step: Wrap the outside of your magnet with a single layer of tape to electrically insulate it. Electrical tape, packing tape, or other types of insulating tape will also work for this job.
In the photo, you can see that my half-inch thick “magnet” is actually a stack of two 1/4″ thick magnets.
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