[annie123 (OP)]

On a (BBC equivalent) radio show someone from a local golf course was interviewed because he was using magnets to affect the flow of water when he watered the course. He said that applying the magnet to the water flow made it spread more easily and further and this was saving him many dollars. The device at an inch long cost $500 and only worked with a small amount of water, but a larger magnet - costing $10 000- was applied to the hose of his sprinkler and somehow this made the water spread further and cover more ground significantly. The interviewer asked how a magnet could affect water like this but the man said he didn't know  - all he knew was it has saved water and money. I have looked n line to find an explanation but without success. It isn't April 1 and this station isn't known for silly interviews, so I would like to know if there is actually an explanation.Thanks.

[evan_au]

If the water were conductive, a magnet adjacent to the flowing water would produce an electric field across the width of the hose. A voltage on the water droplets could conceivably have some effect on how the water droplets spread out in the air. However, the voltage is lost as soon as the water leaves the immediate vicinity of the magnet, and fresh water is not conductive.

In an MRI machine, magnetic fields are used to align the magnetic fields of hydrogen atoms in your body - but this requires very strong magnets (usually superconducting), and the effect only lasts for at most 200ms. It takes a very sensitive radio receiver to detect the signal, and I doubt it could overcome the surface tension of water.

So I think the greenkeeper has fallen for a very expensive scam. He could have done much better by using a different nozzle on his sprinkler.

On the other hand, if he wants to make use of his expensive hose magnets, and save even more money on his water bill, he could water the greens with sea-water, which is electrically conductive. [Don't try this on your lawns at home!]

[PmbPhy]

If the water were conductive, a magnet adjacent to the flowing water would produce an electric field across the width of the hose.

I don't understand. Why is that? Since water molecules consists of charges and there are charges moving through a magnetic field have a magnetic exerted on them. Does it have something to do with that?

[RD]

A strong magnet can repel water , but the effect is minute ...

[PmbPhy]

A strong magnet can repel water , but the effect is minute ...

Oh man! I hate watching YouTube videos.

[jccc]

A strong magnet can repel water , but the effect is minute ...

Awesome video!

Force over mater without contact.

[evan_au]

If the water were conductive, a magnet adjacent to the flowing water would produce an electric field across the width of the hose.

Why is that?

This is the basis of the MagnetoHyroDynamic generator (MHD): A conductive fluid (like salt water, molten salt or a hot plasma) passing through a magnetic field will tend to have the positive and negative ions deflected in opposite directions.

The separation of positive and negative charges across the flow represents a voltage difference that could (in principle) be used to generate electricity. In practice, turbines combined with rotating generators have been much more popular up to the present time.

[Bored chemist]

Just for the record, water is a conductor, albeit not a very good one.
Tap water will be much more conductive- say a hundred to ten thousand times more so.

[annie123 (OP)]

Thanks for the replies - but I'm not much the wiser and although I have asked the radio people to explore this and tell me what they find I haven't had any success yet. I will try and get hte golf course person to tell me which company is supplying him with this supposedly scientific cost reducer.

[JP]

It sounds like a scam working off peoples' desire to conserve water.  The effects discussed above will be tiny compared to mechanical effects such as hose/sprinkler design and water temperature.  There's also the fact that unless you carefully measure the water flow pre- and post-magnet, your mind can fudge things to make it seem as if the $10,000 device you got is actually working.  My guess is that they're just trying to conserve water more carefully now that they've installed it and that they could have gotten the same level of conservation pre-magnet.

Aside from this, magnets have a history of being applied to do all sorts of things to water.  Some are plausible, but many are fantasy.  We've had threads on magnetic water softeners (which don't seem to work reliably, but may do something in some cases) before.  You can find a lot more here: http://www.chem1.com/CQ/magscams.html