Thread: Which is more dangerous- shock due to ac or dc?

AC is a Alternating Current. It has positive half cycle
and one negative half cycle. At positive cycle it wll
atract human beings and negative half it will repels. But,
DC is a direct current. It has only positive cycle. The
shock will absorb human being and it will fully suck the
blood and then remove then only dc is dangerous

Any suggestions regarding this?

_________

ged test
Manager Education

Electricity does not attract or repel human beings. Both ac and dc are dangerous and can kill. Neither will suck your blood.

AC has the effect of contracting and releasing your muscles at a pretty high rate 50-60 hz normally. This release point makes it slightly easier to "let go". DC on the other hand will cause your muscles to contract and make it pretty much impossible to "let go". The burning of flesh follows. RF can be really nasty however.

Originally Posted by (In)Sanity

AC has the effect of contracting and releasing your muscles at a pretty high rate 50-60 hz normally. This release point makes it slightly easier to "let go". DC on the other hand will cause your muscles to contract and make it pretty much impossible to "let go". The burning of flesh follows. RF can be really nasty however.

It is kind of funny, but you can let go of standard AC current. Unless it is Arcing, and causing a higher frequency, and perhaps higher voltage. Then you cannot let go of the high frequency, high voltage, AC current. I have been stuck to high frequency AC current. Not a happy place.

DC can as you say send you flying, or lock your muscles. It has stood me straight up faster then my Gunny Marine Uncle could. And that is fast.

DC tends to only mess with you if you are wet. If you are dry you will be hard pressed to feel 400 volts across your finger. I know, I was sitting one day for a few minutes and the capacitor with over 400 volts did not discharge into my finger. I had my finger across the two poles of the charged capacitor. I was really worried because I thought the capacitor had discharged. I got the meter out, the capacitor was still at 400 volts DC. I put my finger on it nothing.

But wet, 12 volts DC is impressive. And at ARC welding voltage and amperage it is highly respectable.

My boat was sinking one day at a beech party I threw many years ago. I was sitting on the beach enjoying the day, and recovering from an emergency jump from the draw bridge. The draw bridge operator, had come out to chase us off the bridge. When I jumped to get away from him, I was kind of going to do a belly flop. So I was swinging my arms like a big bird trying to right myself.

I kind of hit the water doing a cannon ball entry. Wow, that is bad for a man, if you know what I mean. I just stayed at about fifteen feet deep, looking up at the light. Wondering how long it would take to float motionless to the surface. At one point I realized too long. So I was able to just kind of make this one handed weak dog paddle gesture, to help me move upwards. It was better to stay motionless then try to swim up. When I got to the surface, I just continued that gesture till I got to the beach. I laid there in the seaweed for 30 minutes, rather still. Then I went and laid somewhere else.
Well as I am enjoying the rest of my day, someone mentioned it looked like waves were coming in over the back of the boat. I got up ran to the boat. It was going under. The charter boats were just coming in, the draw bridge opens for them. One after the other.

I already knew I either killed the battery, or the bilge pump or automatic float switch had failed. On or near salt water this can happen one to ten times a season. A wire had corroded off inside a crimp on connector. So now I am kneeling hip deep in salt water to get to the battery. I touch the battery terminal, marked (+), and I feel it rather well. The boat is grounded with the (-) terminal.

I am not going to let this thing sink. So I take the wire that corroded off, and hold it onto the terminal. It feels very strange. As if you are running and using up all your energy.

I only had enough strength to hold it onto the terminal. I was losing all my strength. I was so tired. But I would not let that thing sink. The boat came back up, just as the next wave of boats were coming in. But it felt like I ran a Marathon.

This is a little off topic but it explains the problem of wiring in a speed boat.

What happens with the speed boats is that you are always pounding them. Sometimes you come out of the water as high as fifteen or twenty feet. When you come down, you are attempting to put the stern in hard to save the boat. You try to goose the motor as you are being thrown into the air by a large wave. To make the boat more vertical.

Basically you try to sink the stern and motor a bit, to absorb the shock of just stopping the hole boat at the surface. Sometimes, you just come down too flat. When you do the forces of gravity, yank the wiring. Creating new cracks for the salt water and moisture to get into. So it is never ending maintenance.

Sometimes you come down totally vertical. Then you hear the motor exhaust gurgle as it goes under. Hopefully you have the right rpm's not to fast or slow, to let the prop grab, and give you enough power to lift the boat. And hopefully you have just enough forward momentum left to knock the nose down. Usually we would move into the wind, to get the maximum effect and height. If the wind is strong enough and you are too vertical, you go over the wrong way.

This one time my friend was driving and he took it to the edge. We had time to look at each other, with a look of horror, because the wind was still taking us back. It seemed like a minute and a half, Ha-ha. But it probably was about three seconds. We just kind of sat there moving forward at about ten miles an hour, totally vertical. And watching the motor go completely under.
At one point, I felt the wind die. And the boat just fell kind of forward and to one side. We just went home slowly after that. Ha-ha. Had a lot more respect for the water.

It was in the bay behind Fire Island we were going out to visit someone that tended the lighthouse. And the winds are fierce out there at certain times of the year.



Sincerely,


William McCormick

Originally Posted by William McCormick

DC tends to only mess with you if you are wet. If you are dry you will be hard pressed to feel 400 volts across your finger. I know, I was sitting one day for a few minutes and the capacitor with over 400 volts did not discharge into my finger. I had my finger across the two poles of the charged capacitor.

I take it either you have a prosthetic hand or experienced these 400 volts one at a time?

I cannot give you an answer, only a fun little historical factoid.

In the early days of commercial use of electricity there was a struggle between Westinghouse/Tesla who promoted AC and Edison who promoted DC. Edison, in order to gain an advantage, claimed that AC was dangerous and demonstrated it by electrocuting several animals. This in turn led to the development of the electric chair as a means of executions.

However from an engineering perspective AC and DC are both equally dangerous because both can theoretically deliver the same amount of power. You might want to post your question to the medical or biology forums where they could give you better answers on the differences (if any) in the effects on the human body produced by AC and DC electrical shocks.

I'm guessing ac due to the speculation that a dc current will take one path to the ground which could by-pass the heart. An ac charge would change with every cycle increasing the probability of going through any major pulmonary area. However, the question does not take into account the amount of voltage or amperage which also makes a difference. Anyway, working with household level electronics, I would still rather a shock from a phone line then an outlet.

In my experience, both household AC and DC pose about the same danger at the same voltage. Keep in mind, it's the current that damages or kills you, not the voltage.

What is more dangerous?

AC at Short Wave radio frequencies starting at maybe 50 watts or more. The body starts acting like an antenna. You don't need to be grounded to receive a shock large enough to kill.

Suppose your rating is 100v d.c and a.c. The dc delivers a max voltage of 100V into your body(say @ 100mA).Whereas a.c will deliver 1.414*100V as the max voltage. This is since rating for ac is rms. But whatever the voltage its realy the current which gets you. A few amps of current even at low voltage con give you quite a shock.

Originally Posted by newton

A few amps of current even at low voltage con give you quite a shock.

A few amps ???
I worked in nuclear physics for many years at particle beam accelerators and I can tell you that as little as 10 milliamps can kill you. That is 0.01 amps.
And it is the energy delivered to your flesh as measured in joules that kills you.

Additionally, there is something called an RF burn when you get energy from a higher frequecy source like a power supply. It burns you inside and your skin bubbles. It hurts like hell and it did happen to me one time when I got across a 400 volt supply. Threw me back ten feet and the burn hurt for a week.
I was lucky not to have been killed either by knocking my head in the fall or too much energy.

Professionals in high voltage areas are never allowed to work alone. Always must have a buddy system in effect. And 50 volts is considered high voltage.