Highly Confused

[kelly528]

In electrofishing the fish are not electrocuted... simply drawn to a current running between 2 forks (anode and cathode), then netted, I believe.

Nope, they get electrocuted and paralysed as a result.

You need to check your facts, I think. They are attracted th the electric current, then stunned when they swim in between the anode and the cathode, I believe. Here is where I am getting my facts: http/www.salishsea.ca/resources/Inventor...ctrofishing.htm

Not when everything's hooked up to a power bar! Actually, most of them come with a switch that cuts the power, but I am so scaredy that I unplug it anyways.

Everything is hooked up to a power bar, but I don't want to have to unplug multiple timers connected to lights, solenoids on CO2 units, HOB's, externals etc. All the timers would have to be re-adjusted every single time, and some of the HOB's need help to get started again. Meanwhile I would have multiple tanks in the dark with no circulation, and gunk from all the filters would shoot out into the tanks, which I dont mind too much on my planted tanks, but not on marine tanks...

Also at work I cant go downstairs and unplug the main marine system pump and everything else just to catch a fish, or wipe a bit of algae, or climb behind cabinets ad navigate a sea of cables to get to the freshwater equipment.

I'll just risk death, thank you very much .

True that. I am just speaking for myself, and... well... you've seen my signature lol!

 

[three-fingers]

Just to add it is a bit like the electrical appliance in the bath killing you myth... Why would electricity rather flow throughout the whole bath than the cm or so between the electrical conductors?

I don't think thats a myth, I think it's a myth that it's a myth .

The reason it would travel throughout the whole bath and kill the person is because water isnt like a piece wire. The whole body of water gets electrified, the space between the metal contacts is part of the whole body of water. The person in the bath is essentially part of the body of water, given that the body is 60% water and is soaked in with it, blood is 95% water and the heart is controlled by electrical impulses sooo...I cant see anyone surviving dropping a toaster in the bath.

Remember messing around with the Van de Graaff generator in physics class back in high school? The more you turn the belt, the higher the potential difference between the electrodes and the further away they static shock could get you from.

I would imagine it being like that in the water. Lighting strikes in the sea and if not everything dies, but I wouldent want o be in the water anywhere near to the strike.

In electrofishing the fish are not electrocuted... simply drawn to a current running between 2 forks (anode and cathode), then netted, I believe.

Nope, they get electrocuted and paralysed as a result.

You need to check your facts, I think. They are attracted th the electric current, then stunned when they swim in between the anode and the cathode, I believe. Here is where I am getting my facts: [URL="http/www.salishsea.ca/resources/Inventor...ctrofishing.htm"]http/www.salishsea.ca/resources/Inventor...ctrofishing.htm[/URL]

The voltage between the electrodes shocks* the fish, which results is muscle spasms making them swim in the direction of the electrodes, and then paralysed when they are close enough. How close hey need to be appears to depend on the voltage.

*I did need to check my facts, not on electrofishing, but on my usage of the word "electrocute".

From Wikipedia:

Electrocution is also frequently used to refer to any electric shock received but is technically incorrect. This choice in definition varies from dictionary to dictionary.

In my post above, I should have said "shocked and paralysed as a result", because that actually makes sense lol.

But other than that, I believe my facts are right.

 

[keenonfish]

I can see what you are saying, and while I agree water isn't like a wire it will still partially conduct due to impurities. Now, as it is primarily current that kills us not voltage and the current that flows through us is directly proportional to voltage divided by (skin) resistance, for the appliance to pose any threat to someone in the body of water would require that the water between body and the appliance provide a favourable path for the flow of current, i.e. a very low resistance. I am sure water has quite a high resistance out the tap, maybe a couple hundred kohms, This resistance in itself would mean a maximum current will be limited to harmless levels. Even if the resistance was low enough, why would there be a large enough potential difference at two points of our body to create a substantial flow of current? I just can't see it happening!

Now sit between appliance and an earthed drain, or bare earthed iron bath and that would be a different story! But I cannot see a problem with modern plastic baths and waste systems tbh.

Anyway, I ain't gonna try it so I guess this one will have to go on the 'fairly certain but not quite sure' shelf for now

Just to add it is a bit like the electrical appliance in the bath killing you myth... Why would electricity rather flow throughout the whole bath than the cm or so between the electrical conductors?

I don't think thats a myth, I think it's a myth that it's a myth .

The reason it would travel throughout the whole bath and kill the person is because water isnt like a piece wire. The whole body of water gets electrified, the space between the metal contacts is part of the whole body of water. The person in the bath is essentially part of the body of water, given that the body is 60% water and is soaked in with it, blood is 95% water and the heart is controlled by electrical impulses sooo...I cant see anyone surviving dropping a toaster in the bath.

Remember messing around with the Van de Graaff generator in physics class back in high school? The more you turn the belt, the higher the potential difference between the electrodes and the further away they static shock could get you from.

I would imagine it being like that in the water. Lighting strikes in the sea and if not everything dies, but I wouldent want o be in the water anywhere near to the strike.

In electrofishing the fish are not electrocuted... simply drawn to a current running between 2 forks (anode and cathode), then netted, I believe.

Nope, they get electrocuted and paralysed as a result.

You need to check your facts, I think. They are attracted th the electric current, then stunned when they swim in between the anode and the cathode, I believe. Here is where I am getting my facts: <a href="http/www.salishsea.ca/resources/Inventor...ctrofishing.htm" target="_blank">http/www.salishsea.ca/resources/Inventor...ctrofishing.htm</a>

The voltage between the electrodes shocks* the fish, which results is muscle spasms making them swim in the direction of the electrodes, and then paralysed when they are close enough. How close hey need to be appears to depend on the voltage.

*I did need to check my facts, not on electrofishing, but on my usage of the word "electrocute".

From Wikipedia:

Electrocution is also frequently used to refer to any electric shock received but is technically incorrect. This choice in definition varies from dictionary to dictionary.

In my post above, I should have said "shocked and paralysed as a result", because that actually makes sense lol.

But other than that, I believe my facts are right.

 

[kelly528]

Is morbid that I have a burning desire to further explore the dynamics of electric currents in water with respect to risk of injury?

PS. I think at least some of all this stuff is legit because it is actually a warning in some of the instructions that came with one of my aquariums... either that or I read it in an aquarium book.

 

[three-fingers]

I can see what you are saying, and while I agree water isn't like a wire it will still partially conduct due to impurities. Now, as it is primarily current that kills us not voltage and the current that flows through us is directly proportional to voltage divided by (skin) resistance,

Bear in mind that the skin would be soaked with water, so would have less resistance than usual too. And there are other, more sensitive areas exposed in a bath that have less resistance...and once the current finds its way to the bloodstream in any way, even less resistance there.

for the appliance to pose any threat to someone in the body of water would require that the water between body and the appliance provide a favourable path for the flow of current, i.e. a very low resistance.I am sure water has quite a high resistance out the tap, maybe a couple hundred kohms, This resistance in itself would mean a maximum current will be limited to harmless levels. Even if the resistance was low enough, why would there be a large enough potential difference at two points of our body to create a substantial flow of current? I just can't see it happening!

You have to take into account the volume of water anyway, but regardless, this is easy to measure . Waters conductivity is frequently measured - in fact, even the new Fluval G filters do it.

Conductivity (k) is the inverse of resistivity ( r ): k=1/r

So : r=1/k.

The more salts and certain impurities in the water, the higher the conductivity.

Sea water has a conductivity of 4.8 siemens per metre, drinking water anywhere between 0.0005 siemens per metre and 0.05 siemens per metre.

Bath water is only ever going to have a higher conductivity, due to stuff from our skin, any bath salts/minerals or other additives. But lets say for bath water r=1/0.05. So the resistivity is 20 ohm metres, and when your soaked in a bath, all the low resistance parts are exposed.

Resistance of 300L of bath water using 0.05 siemens per metre:

R (resistance) = r length/area of material.

In this case 300L of water, so 20 ohm metres x 0.3 metres /1 metre squared.

20 x 0.3 / 1 = 6 Ohms.

So using Ohm's law V=IR , I=V/R , I=230/6 = ~ 38 amps.

Drop a toaster into a bath with 300L of tap water and your looking at 38 amps going through your body.

From wiki: Death can occur from any shock that carries enough amperage. Small amperages (40 mA - 700 mA) usually trigger fibrillation in the heart which is reversible via defibrillator, but large amperages (> 1 A) cause permanent damage via burns, and cellular damage.

Now sit between appliance and an earthed drain, or bare earthed iron bath and that would be a different story! But I cannot see a problem with modern plastic baths and waste systems tbh.

Most electrical appliances are earthed...and if you drop one in the water...it doesnt matter if the bath is earthed.

Anyway, I ain't gonna try it so I guess this one will have to go on the 'fairly certain but not quite sure' shelf for now

I'd place it on the "not going to be toasting anything while enjoying a bath " shelf .