Thread: For the scientifically minded...

I was just wondering about this as I got a minor electric shock this morning while working on some wiring.

We all know electricity is defined as a flow of electrons. But what does that really mean and what would it take to completely reverse or stop that flow. Also, how would either AC or DC differ in those respects. C'mon I know we have some Physicists here.

Electricity is like running water. You have to have "flow" for it to work. If you stand on something insulated from ground, you will not get shocked because the electricity has no "path" to ground. Hope this makes sense. BTW DO NOT TRY THIS UNLESS YOU HAVE SOME EXPERIENCE. IF YOU DO NOT HAVE THE PROPER INSULATION YOU WILL GET SHOCKED!

Or you could do what i did and accidentally bridge 120V AC between your thumb and forefinger... then not be able to use your hand for the rest of the day.

AC - the current alternates polarity, so if you get shocked, you have positive and negative current flow very rapidly.
DC - the current is always the same polarity, so if you get shocked, its positive current flow only.

How bad a shock is depends - among other things - on where it is. my example of thumb to forefinger was not a bad shock. 120V DC would not be a bad shock in that circuit either. if that had been from thumb to thumb, I'd probably be pushing daisies.

You can survive a massive shock if the amperage is low enough. example: Tasers are something like 40,000V DC at a very low amperage(measured in miliamps) - they are rarely lethal. Conversely, if the amperage is high, a lesser shock can kill you. a car battery can kill you, but its only 12-15V DC. Car batteries produce anywhere from 300 -1000 Amps.

Confused yet, or should I mention wattage?

It generally stops if you don't pay the bill.

Originally Posted by 96firephoenix

You can survive a massive shock if the amperage is low enough. example: Tasers are something like 40,000V DC at a very low amperage(measured in miliamps) - they are rarely lethal. Conversely, if the amperage is high, a lesser shock can kill you. a car battery can kill you, but its only 12-15V DC. Car batteries produce anywhere from 300 -1000 Amps.

While it is true that current is the killer, current is a function of voltage & resistance.

Your body can be compared to a giant electrical resistance.

So the current that can flow in your body is DIRECTLY related to voltage being applied to you.

Here's a pretty well written article explaining the phenomenon better than I can.

Ohm's Law (again!) : ELECTRICAL SAFETY

Originally Posted by Glenn24

While it is true that current is the killer, current is a function of voltage & resistance.

Your body can be compared to a giant electrical resistance.

So the current that can flow in your body is DIRECTLY related to voltage being applied to you.

That is basically right.

To put this in easier language:
I can touch the Live and Neutral in a regular outlet. This will hurt, but represents little danger or damage to a healthy person. The reason is that you connect in paralell, and the resistance in your body is really high.
According to Ohm's law, it shows like this:
Voltage/(Apmps*resistance)
This closed circuit has very high resistance and therefore low current.

Now, the real danger is in a regular light switch.
Touching the two wires in one of those, with e.g. a bunch of lightning fixtures attached to it, is a real danger.
That will make a serial connection, and that means that all current in that closed circuit will pass thru you.

Believe you me, you do not wanna try that at home. I've lost 2 colleagues this way, a very nasty way to go...

A current as low as 30mA (that's 0,003A) could be potentially leathal, so beware

Originally Posted by thebigspendur

I was just wondering about this as I got a minor electric shock this morning while working on some wiring.

We all know electricity is defined as a flow of electrons. But what does that really mean and what would it take to completely reverse or stop that flow. Also, how would either AC or DC differ in those respects. C'mon I know we have some Physicists here.

In reply to Ohm's law from a former EE, resistance is futile!!!

Originally Posted by Birnando

That is basically right.

To put this in easier language:
I can touch the Live and Neutral in a regular outlet. This will hurt, but represents little danger or damage to a healthy person. The reason is that you connect in paralell, and the resistance in your body is really high.
According to Ohm's law, it shows like this:
Voltage/(Apmps*resistance)
This closed circuit has very high resistance and therefore low current.

Now, the real danger is in a regular light switch.
Touching the two wires in one of those, with e.g. a bunch of lightning fixtures attached to it, is a real danger.
That will make a serial connection, and that means that all current in that closed circuit will pass thru you.

Believe you me, you do not wanna try that at home. I've lost 2 colleagues this way, a very nasty way to go...

A current as low as 30mA (that's 0,003A) could be potentially leathal, so beware

Actually, you got that backwards my friend.

If you leap yourself onto the black and white lead (US standard) of an otherwise unhooked electrical circuit you have entered yourself into a series connection and have become the load. It's all you, baby! Ride the Tiger!

If those wires are connected to lighting circuits - or other circuits that are in use - you are hooked up parallel. You'll get the same ride as you would in series. Your load is just added- by about half in fact - to the load that's already in use, but you are just one component of the 'new' circuit. Ohm's law is a constant in the universe.

If however you decide to open up the return and jump into series with that Tiger... let's hope you wake up after you hit the walls.

I always tell my guys to beware of the white wire. That black one will bite, but if it's still hooked up the white one will clack your nuts together and tattoo their names on your forehead.

I suppose any voltage that hits home 'could' kill, but up to 277 you'll instinctively let go. You might have to wash your mouth out with soap, and add an extra bit to the wash to clear out those undie scars, but you will let go.

Higher voltages and you run the risk of having your motor functions altered. If you can't let go, that's a bad thing. Very bad.

Originally Posted by thebigspendur

what would it take to completely reverse or stop that flow.

Turn off the switch.

In your basement there should be a big grey panel. Go find it and open it. There should be a bunch of switches in there with a couple large ones at the top. Flip the large ones. Now the flow of electricity into your home has been stopped. If you want to reverse the flow you'll need your own source of electricity such as a generator or solar panels, to hook up and send out.