Analysis of current flow and EM fields in seawater?

[vwrobc]

Hi, I have a few queries regarding the flow of electric current through (sea)water...

In general, can the flow of electricity through seawater be treated the same as through a metal conductor?

I am wondering whether the fact that it is ions rather than electrons that carry the charge has any affect?

If a current flows between two point source electrodes, what would the field patterns look like? I'm assuming the field strengths decay exponentially (as per skin effect) in the plane perpendicular to the direction of current flow. Is this correct?

Thanks for any guidance you can offer!
Rob

 

[AJ Bentley]

The quick answer would be yes and no.

The flow of electricity in matter isn't a simple thing - even in conductors there are complicated things going on. When you add in the tendency of liquids to slosh around and the complication of the ionic currents that could form, it tends towards chaotic.

From the point of view of Physics, it isn't a terribly interesting question. (Complicated, chaotic systems are just not worth bothering with - they give no insight into the basic mechanisms behind phenomena.)

To an Engineer, it might well be, but then you would have to be very specific about which liquid and under what conditions.

 

[alxm]

It's similar in some ways and dissimilar in others, you have to be a bit specific. The fields definitely decay rapidly - water has a high dielectric constant.

There's no limit to how deep you can delve into this question, since we're talking about the whole field of electrochemistry basically. Direct current or alternating current? With alternating current you end up with a very high impedance, so it's not really feasible to lead commercial power lines through seawater.

But it is for DC, and there's a good number of underwater HVDC transmission systems that lead the return current through the water, meaning you only need one submarine cable. (for instance the http://en.wikipedia.org/wiki/Baltic_Cable" connecting Germany and Sweden)