Need advice on electro magnetic boat

[monrosm@shrewsb]

I need help with a question that has been puzzling me.
It probably has a name, but there is a propulsion sytem that uses a copper bar which is fixed under a boat, a large current is passed through it which causes an electromagnet to produce a vertical magnetic field. Using flemmings right hand rule (first finger field, second finger current and thumb as thrust or force) this should propel the vessel through the water. However it doesnt work. Im trying to answer an A level advanced physics question which asks me why this does not work? Any ideas....have a hunch that it could be to do with water only having a small charge. But i could be way out....any suggestions are helpfull as i have none.
Once again any suggestions helpfull.
Thakyou
Stef

[alan white]

Induction? There are electric automobile charging systems that work on that principle. Something similar should be found in googling water valve that have no mechanical connection from inside to outside the water vessel----- if water didn't interfere.
Another question, would distilled water work best and saline worst?

Alan

[messabout]

Explain the apparatus more thoroughly. You have mentioned copper bar, large current, electromagnet, and magnetic field.

The electromagnet is presumably some sort of coil wound over a ferromagnetic core, Applying a current to the coil will produce a magnetic field. That field could induce a current in the copper bar which would produce a local magnetic field around the bar (mutual induction). If the current in the electromagnet is DC then a field will develope, but induced current will occur only while the primary current is rising or falling. If applied current is AC then there will be an alternating reversal in the part that has recieved the mutual induction. If any of that resulted in the generation of a force, then the reversing, north/south poles would cancel one another in terms of a force vector.

The electromagnet and the copper bar need to be close together to minimze the affect of the inverse square rule (Coulombs Law).

Even if we could get some kind of directional force to be produced by the copper bar, then we'd need something to react with that force in order to produce propulsion. (Newtons first)

This scenario sounds like the examiners have thrown in a "low ball" question just to mess with your head.

[tom28571]

Originally Posted by messabout

Explain the apparatus more thoroughly. You have mentioned copper bar, large current, electromagnet, and magnetic field.

This scenario sounds like the examiners have thrown in a "low ball" question just to mess with your head.

Sounds about right.

[Guillermo]

Stef,
Are you talking about magnetohydrodynamic propulsion?
Here an small and easy experiment: http://www.evilmadscientist.com/article.php/SimpleMHD

[RatliffFranklin]

Originally Posted by monrosm@shrewsb

I need help with a question that has been puzzling me.
It probably has a name, but there is a propulsion sytem that uses a copper bar which is fixed under a boat, a large current is passed through it which causes an electromagnet to produce a vertical magnetic field. Using flemmings right hand rule (first finger field, second finger current and thumb as thrust or force) this should propel the vessel through the water. However it doesnt work. Im trying to answer an A level advanced physics question which asks me why this does not work? Any ideas....have a hunch that it could be to do with water only having a small charge. But i could be way out....any suggestions are helpfull as i have none.
Once again any suggestions helpfull.
Thakyou
Stef

The magnetic field has to make saltwater flow from the bow of the boat toward the stern to generate forward thrust.

[juiceclark]

I saw a show about this on the History Channel once. An experiement was done at a university with a canoe sized craft powered electromagnetically. It worked! But the darn thing just barely crawled along. I can't find the video online anywhere...will look again.

Tony

[eponodyne]

So you want the whole lash-up to dissolve into a pile of rust in six months? What kind of efficiency does that bring, other than a tax write-off?

[messabout]

Check out Guillermos' suggested site. There is great fun there, especially for those who do not have enough to think about.

Guillermo; How is it that you are a fountainhead of information and references? Not just on this thread but on many others and many subjects. Thanks for all that neat input.

[Guillermo]

Hi, messabout! I suppose I just google around very efficiently..

Cheers.

[messabout]

The October 2007 issue of Scientific American has an article about portable micro labs. A flash drive sized unit that is able to diagnose anthrax, HIV, E-coli, influenza, and a lot of other things. The diagnosis chip takes maybe 10 minutes to arrive at conclusions that takes hours in the normal fixed laboratory. Wait a minute guys, I'm getting to the part about boats.

The device takes a droplet of fluid from the individul and squeezes it through a bunch of extremely tiny channels and valves where it is mixed with various reagents, Ultimately delivering a diagnosis. Fluid does not like to go through those tiny channels and some motive power must be introduced. The original experimenters at Univ. of Michigan used air pressure to push the fluid. The method had some drawbacks because of size constraints for the air supply element. Some gee whiz people at MIT rigged up an electrical motivator. The process is called electroosmotic flow. they make the fluid move, despite the resistance of the constrictions. Not only that but they have found that they can persuade the fluid to move with AC current better than with DC. Right; this is mass movement on a nano scale but the science is apparently there. How long it takes to apply the principle to boat propulsion remains to be seen.

No doubt the examiner, the one that I impudently accused in a previous posting, knows more than me. He is demanding much of his student but perhaps that is a way to engender brilliance.

[CDK]

Here's another exotic way to power a boat:
Spray the bow area with a water repellent like wax or silicone and clean the stern with a scotchbrite pad.. The water surface will curve downward towards the bow, while at the stern it will curve upward. The water level at the stern will be higher than at the bow so the boat (according to Archimedes) will move forward. No fuel, no electricity, no noise!