When a 12 volt auto battery is totally submerged in water, it retains its charge. Why doesn’t the water, a good conductor, cause it to go dead?
I have no idea.
I remember a condutance demonstration - Teacher put his finger into a container of recently-distilled water and put in a live wire (with a low-tolerance circuit breaker so he wouldn’t kill himself even if he touched it directly). Nothing. Pulled out his finger, put in a second wire which led to a light bulb, which led back to the box, supposedly making a circuit. Nothing.
Teacher pours in a little salt. Light glows. A little more salt and light gains full intensity.
Pure water is incapable of carrying charge. Charged particles can carry charge just fine.
I learned in a later lesson that water is never pure, but a solution of itself - a few H and OH ions were in that container. So perhaps a small amount of current was passing, but not enough to pose a danger or light the bulb. It wasn’t until salt dissociated into the water that there was enough ion to carry the electricity.
IANAElectrical Engineer, but my WAG is that the voltage isn’t high enough to overcome the resistance of the water. Contrary to popular belief, water is non-conductive. Dissolved materials will make it conductive, but I’d imagine that the conductivity would vary widely depending on how pure the water is. Most electrocutions you hear about occur via house current, which is 120VAC. Hopefully someone more well informed than I am can give you a real answer.
Add some salt to the water and then try your experiment. The battery will probably heat right up.
I wonder what purity water you are putting your battery into.
I somehow think that tapwater would have plenty of sh… stuff dissolved in it. Mine does. You should see the stuff first time you turn it on in the spring on the outside faucet! Of course, that must bne the pipes rusting. Still dirty.
Thanks. It’s not really an experiment, though. The bilge pump on my little skiff went kaput during a hard rain, and the battery well filled up with water. It was several days before I got an opportunity to pump the water out and fix the bilge pump. I had assumed the batteries (there were two of them), being totally submerged for several days, would be completely discharged. But they checked out as fully charged.
While it was mostly rainwater, the open boat certainly wasn’t clean. I was a bit mystified about why the batteries were still hot.
Yeah, I’m still guessing that the voltage wasn’t high enough to overcome the resistance the water posed.
I happen to be an electrical engineer. Water, despite hollywood hype to the contrary, is actually a fairly poor conductor. It gets to be a better conductor when certain impurities are added to it, but even then it never really becomes a “good” conductor like copper or other metals. Rain water is fairly pure, and as you discovered it doesn’t conduct well enough to kill your battery.
The reason electricity is so deadly to humans is because house voltage is fairly high, and your body is very sensitive to very small amounts of currents. A lot of voltage applied through a very poor conductor gives you a little shock, but that’s enough. A shock that you are barely capable of feeling is more than capable of throwing your heartbeat out of whack, and the design of your heart is such that once it gets out of whack it tends to stay out of whack. If someone is standing next to you with a portable defib machine you’ll probably be ok, otherwise it’s time to make funeral arrangements.
Thanks, e_c_g. I guess I forgot what little high school physics I may have learned. And that was a really loooong time ago. I confess to not knowing that pure water is a poor conductor, but now I emerge from the ignorance, and understand why the batteries weren’t dead.
A friend commented recently on having had the same experience with his boat batteries. I’m looking forward to the opportunity to casually flaunt my new-found knowledge.