I understand the bird on a wire thing. But why do i not get shocked when there is a ground probe but the fish would get shocked with a groubd probe? Doesnt make sense.
Stray voltage and grounding probes
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redfishbluefish
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My guess....a paper cut feels like you're getting zapped....but it's just the salt doing it's thing on a cut.
Try using a multimeter to see if you actually have voltage. The only issue is that it can't discriminate between actual leakage and induced voltage.
Try using a multimeter to see if you actually have voltage. The only issue is that it can't discriminate between actual leakage and induced voltage.
OP
OP
Well this is the theory not what ive experienced. The theory that a fish will get electrocuted with a ground probe and without one wont because your providing a path to electricity to ground. But then the contradiction is that i wont get electrocuted with a ground so its safe for me but not for the fish. Wow confused.
scriptmonkey
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@Brew12 school us please.
My understanding... It's all about the path to ground. If there is no path to ground the fish are fine because they are part of the circuit and there is no difference in voltage (potential energy) once you add a path to ground the current flows through the water like a wire (kinetic energy). The ground probe protects you because it's the better path to ground so it chooses that instead of you. Without the probe you become the path to ground and you are now the wire. Like you mentioned, same as a bird on a wire or high voltage line worker can touch the wire as long as there is no path to ground. Voltage is the "difference" between 2 wires and it wants them to be the same so it tries to even out the electrons between the two.
OP
OP
So the fish become like a resistor in the path of electrons, heating up and slowing the flow of electrons maybe? But what about me? I wouldnt act as one?
OP
OP
Okay another thought, what would happen if a fish ate some activated carbon with amperage in the water? Since activated carbon is an excellent conductor of electricity wouldnt a fish get electrocuted without a ground probe even?
OP
OP
Lol i hope not. Mass has resistance. Resistance has density. Density would slow electrons. This is my thinking about a fish that ate carbon while amperage was present.
chinw76
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Carbon actually has a high resistance. It is used in resistors to resist electricity in an electrical circuit board. I work with 480V AC and 600V DC all the time at work. I can can touch anything that is not grounded while touching a live wire. I personally use a grounding rod in all my tanks. Yes it is to protect me, since I will have more resistance to ground. It will not bake the fish if there is a short. The fish would not be in a path of the current in the water. That is why I made the joke of putting the grounding rod in the fishes mouth. If the fish has its back half in the water with electricity, and the top half is out of the water with the grounding probe shoved down its throat, then yes, it will get zapped that way. The fish is then directly in the path of electricity, it would flow through the fish to the grounding probe. That fish would then be fried, but all the others would be ok. The reason being that the fish are not in the direct path of the electrical current.
Take the bird on the electrical wire. The bird is fine standing there, but if you shove a grounding probe in its mouth, it is fried. Now lets say that bird is still on that wire, and a few house down from the bird the line breaks and touches the ground. That line is now grounded, it will be jumping all over the place when it touches the ground. The bird will still be safe because it is not between the electrical current and ground.
Take the bird on the electrical wire. The bird is fine standing there, but if you shove a grounding probe in its mouth, it is fried. Now lets say that bird is still on that wire, and a few house down from the bird the line breaks and touches the ground. That line is now grounded, it will be jumping all over the place when it touches the ground. The bird will still be safe because it is not between the electrical current and ground.
OP
OP
Yes that makes sense. Good we got an expert here. This is my thought, a fish is not on the wire its like as if it were in the wire. no? Does that make a difference?
Ok another thought. When you work on high power lines, you cannot have any metal on you at all or youll be hurt no? Wouldnt carbon act like this inside a fish?
erk
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chinw76 explains it well.
This is also why if you need to touch a live circuit, whatever the reason may be, you use your right hand versus your left. If you use your left, the current will go thru your heart and kill you. Right, it will just mess you up, but less likely to kill you. A grounding probe is still a good idea. It gives current a direct path, where as no probe means the second a ground connection is made, all current goes thru it.
When I walk onto the manufacturing floor at work or go into the lab, I have to ground myself prior to touching any ESD sensitive equipment. This doesn't protect me from shock, but it protects the sensitive hardware from being destroyed. All depends on what you are trying to protect.
erk
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It's all about the path to ground. Where does the path lie? Just because you have metal on yourself doesn't mean you will conduct electricity. That current has to have somewhere to go.
In terms of the fish, the grounding probe helps to provide a direct path to ground besides you. The fish are at risk if they are in the path. That's why you place the probe in the sump, close to the equipment. Not in the display. When you touch the water, you are providing a parallel path for current. This means some current is going thru you, but because your resistance is higher than that of the grounding probe, majority of the current is passing thru the grounding probe. It all follows Ohm's law.
V=IR
If the grounding probe has a large resistance placed on it, then you touch the water, the current will split between you and the grounding probe as shown in a current divider. You still have current passing thru you with a grounding probe, but the ratio favors the probe, not you.
https://en.wikipedia.org/wiki/Current_divider
Remember though that the water is all a conductor and certain objects in the water have higher and lower resistance. If a fish has more resistance than the water surrounding it, then the current will pass around it. If the fish is lower, then current will pass thru/across it.
erk
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Think of it also like the water in your aquarium. You have a return pump with piping/tubing to the display. The pump is like a battery, it creates pressure, and the fluid moves from regions of high pressure to low pressure, i.e. your display tank. Pressure is like voltage, flow rate is like current. If you crack the pipe, then you create a grounding point, i.e. you have a region of lower pressure that the fluid will travel to.
It is all conservation of energy.
Kinetic Energy + Potential Energy = 0
It is all conservation of energy.
Kinetic Energy + Potential Energy = 0
chinw76
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So the bird on the wire thing. If you cut the wire, and put one end of the wire to one side of the bird and the other wire to the other side, then the bird is fried because all the power is flowing threw the bird.
When I am touching live power, I can have rings on ect. I can touch anything that is not grounded. So let say I am holding 480 Vac in my hand and I touch cardboard boxes, I am fine. The my friend Joey comes by and has his hand touching a grounded electrical panel and at the same time shakes my hand. Now that 480 Vac travels through my hand, through my body, out my other hand, then through Joey's hand, through his body and out the other hand that is touching the grounded electrical cabinet. We became the wire to ground, same thing goes with the bird.
When the fish is in the water, the fish has voltage all around him. Tanks that are not grounded have around 30-40 Vac in the water. This comes from leakage, or magnetic fields given off by pump motors. This voltage may cause health issues over the long term, this is a debated subject. When you add a grounding probe, all that voltage goes right to ground. The fish is not the single point of contact to the ground, so the fish would be safe.
scriptmonkey
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Hmm... going to grab my meter and check for voltage. I have a probe, never used it.
Keepswiming
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Why is your fish eating activated carbon? Long night on the reef ehh?
Brew12
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Hey guys, sorry for getting here late. Looks like a lot of interesting discussion!
But... since we are talking about it... imagine a rubber ball inside the wire strands. Energize the wire to 120V with no load on it. Almost no current flows through the rubber ball. Now put a 10A load on the wire. Still, almost no current flows through the rubber ball. Why? The vast majority of current flows around the rubber ball because the rubber ball has a much higher resistance than the wire.
Our aquariums are much the same. The salt water is much more conductive than the fish so most current will flow around the fish. If you think about your aquarium as a block of copper with a few insulators in it, can you ever get the insulators in the direct path of current flow? Absolutely not. Our fish are the same way.
And then there is the issue that voltage itself only has meaning when compared to a reference. To get current to flow you need a difference in voltage and voltage can't really be felt. We only feel current. If you are wearing rubber shoes and touch a 120V wire your body will become 120V but you won't feel it. I've been energized to 35,000V in an insulated bucket truck before and it feels no different than working on something de-energized. Since fish live inside a conductor they can never experience a meaningful difference in potential.
This is one of the better analogies that I have seen. I don't particularly like any of the analogies involving a bird on a wire but this one doesn't make me cringe like most others.
But... since we are talking about it... imagine a rubber ball inside the wire strands. Energize the wire to 120V with no load on it. Almost no current flows through the rubber ball. Now put a 10A load on the wire. Still, almost no current flows through the rubber ball. Why? The vast majority of current flows around the rubber ball because the rubber ball has a much higher resistance than the wire.
Our aquariums are much the same. The salt water is much more conductive than the fish so most current will flow around the fish. If you think about your aquarium as a block of copper with a few insulators in it, can you ever get the insulators in the direct path of current flow? Absolutely not. Our fish are the same way.
And then there is the issue that voltage itself only has meaning when compared to a reference. To get current to flow you need a difference in voltage and voltage can't really be felt. We only feel current. If you are wearing rubber shoes and touch a 120V wire your body will become 120V but you won't feel it. I've been energized to 35,000V in an insulated bucket truck before and it feels no different than working on something de-energized. Since fish live inside a conductor they can never experience a meaningful difference in potential.
