Can I jump in with a slightly OT question? If I was sitting in the bath and the hair dryer (which is plugged in, fell into the bath. Would I get a shock if I didn’t touch the dryer?
It doesn’t take much current to feel a shock. You can detect currents as small as about 0.5 mA or so (0.0005 amps). Around 5 to 10 mA (0.005 to 0.010 amps) your muscles start to involuntarily contract due to the current. Most safety standards in the U.S. are built around a 5 mA threshold. Currents below that level generally will not throw your heart into fibrillation. Between 5 and 50 mA, the chance of fibrillation increases fairly dramatically, and between 50 and 500 mA the chance of fibrillation is fairly high.
Your heart has kind of a funny design in that if you can throw it into the fibrillation state, it will happily stay there. Instead of beating, your heart just kinda shakes and doesn’t pump blood. You pass out within a few seconds and die shortly after that (unless someone happens to be standing next to you with a portable defibrillator, and even then your chances aren’t all that great). Even at currents of 100 to 500 mA, fibrillation is still a bit of a hit and miss kind of thing. Some of it depends on exactly when you get shocked, as your heart’s rhythm is more sensitive to disruptions during certain parts of its cycle than others.
Above an amp or so, instead of going into fibrillation, the heart muscles tends to just clamp. At that point your heart isn’t pumping blood, so if someone doesn’t remove the source of current pretty quickly you’re in a whole world of hurt. However, once the current is removed, the heart will usually start beating again on its own. So oddly, the fatality rate starts to drop as the current increases around a half an amp to a couple of amps.
Once you get above a few amps, though, then burn damage starts to occur, and this is less hit and miss than fibrillation. This is how the electric chair kills you, it literally cooks you to death, and it’s not very hit and miss. It’s pretty much fatal all the time.
So basically, you start out with a tiny shock that you can barely feel, and then the risk of death increases, decreases, then increases again.
In a modern house, as soon as the hair dryer hit the water and the current from the motor and heating coils started to flow through the water, the GFCI would detect that not all of the current was coming back through the neutral and would shut the circuit off before you received much of a shock.
In an older house that doesn’t have a GCFCI, it’s not really like Hollywood where the entire water becomes magically electrified. You will end up with voltage gradients through the water as the current basically spreads out through it. How much of a shock you’ll get depends on exactly where your body is with respect to these varying voltage levels, but most likely you’ll just feel a slight tingle at worst.
Depending on how exactly you move around and whether or not you touch the hair dryer, you could end up with either very little of the current flowing through your body or most of the current flowing through your body (which could easily be fatal). So this isn’t exactly a safe experiment to try at home.
In an AC system, the resistance to ground can be infinite and it’s *still *possible for you to receive a shock. This is due to capacitance; if your capacitance to ground is high, you could feel a shock even if the resistance were very high. If your capacitance to ground is 10 μF, for example, your impedance to ground would only be 265 Ω (assuming f = 60 Hz). With a peak voltage of 170 V, you’ll feel it.
This is what I was thinking of, that AC and DC work differently regarding their “shockablity”. The other thing I have heard of is that DC is more dangerous because it cause you muscles to contact and stay contacted so you tend to end being unable to release what is shocking you.
So I assume that if I had a DC source of 1000V with the negative bolted to the dry cement floor and I touched the positive while standing on the floor 1m away with my bare feet I would probably feel nothing while if it was 1000V AC it would be quite a different story.
I think some of the confusion in this thread is WHERE the neutral is grounded. Although I am not a licensed electrician, I think it is grounded at only one location, ideally, near the service entrance, not at multiple locations. If a voltage potential of sufficient magnitude occurs somewhere else in the system, it indicates a possibly dangerous fault. That’s the whole point of the ground wire, to provide safety.
This is right - the safety ground and neutral should be bonded in exactly one place, generally the main panel or the meter, and nowhere else. Even subpanels are supposed to keep neutral and ground separated. That ensures that there is only one neutral return path for current and that the ground wire never carries current unless there’s a fault. Say you had a subpanel and you forgot to isolate the neutral bussbar from the chassis, and the neutral wire between the subpanel and main panel broke. Now all your return current from the subpanel would travel to the main panel via the ground wire, because ground and neutral were connected at the subpanel. That’s very bad! If ground and neutral are separated, then a broken neutral would cause the subpanel to stop working in an obvious way and it could be fixed.
you would find your neutral attached to a ground rod (buried below your electric meter) or a metallic water service entrance if you have city water. which method would be appropriate for the time period.
the utility will put a ground rod in at the meter which the neutral connects to.
in a typical house you might have more than one grounding rod (for a safety ground), if needed or desired, separated by 6 feet or less. this is effectively a single grounding location
if you had locations like a detached garage or shed more than 50 feet away you would put in another safety ground (using a ground rod).
there is an electrical code and good electrical practices filled with much detail. there are all kinds of special cases and exceptions. doing it right takes considerable know how and experience. the electrical code in the USA is a really big complicated book.
Which is how a defibrillator works. You have a heart in fibrillation, you give it a big enough shock to stop it, and then you hope that it re-starts in pumping mode like it’s supposed to.
Short answer: Assume you will get a shock.
Long answer: You might get a shock, but sometimes not.
Some previous talk seems DANGEROUS, eg saying that the -ve is ground… Grounds fail … Grounds can be floating. Assume that you will get a shock, as 100 to 200 V DC is quite strong and deadly depending on circumstances