Electrical shock

[luggem]

Is the severity of a shock ever depend on the load?
I beleive according to Ohm's law, that it is only a matter of the voltage and the body's resistance from hot to ground. My co-worker says no, its a matter of how much load is on the circuit. Please tell me who is right.

 

[roger]

You are both saying the same thing, the resistance of the body is the load.

If the body is dry the resistance is higher than if the body was sweaty, and in the latter the resistance would be lower (a greater load) and the shock more severe.

Roger

 

[nakulak]

I believe what your friend is indicating is that there is already current flowing when a circuit has a load on it, rather than a circuit which has no load. I am not knowledgleable enough to know if there is a difference. However, if the voltage on the circuit is greater than 30 volts it can kill you, so whether or not its under load is, in my thinking, irrelevant. As long as there is a potential of 30 volts or more, and the ckt can deliver more than 6 milliamps, it can kill you.

(and as the guy above me said - once you complete the ckt you are the load)

 

[zog]

You are right, your friend is wrong if he is saying you would get a more severe shock from a 480V system with 1000A load than a 480V system with a 100A load, in that sense load makes no difference.

 

[charlie b]

The person getting shocked is essentially a resistor in parallel with the load. Both the load's resistance and the person's resistance will have the same voltage applied. Therefore, the amount of current going through the person's body will not have anything to do with the amount of current going through the load. The current in any one of two parallel resistors depends only on the value of its resistance and the value of the applied voltage.

In the discussion above, I have disregarded the very, very small change that takes place inside the voltage source, each time new load is added to the circuit. That change is a reduction in the output voltage of the source, and takes place because of internal resistance within the source. The higher the original load current (i.e., prior to the person getting shocked), the higher the current will be through the source, and thus the greater the voltage drop internal to the source, the lower the value of voltage at the terminals at the source, and the lower the voltage will be when the person touches the circuit. Therefore, if you take into account small changes inside the source, your friend's statement is correct (i.e., the shock does vary with the amount of the original load). However, the difference will not be enough of a reduction to change the person's chances of survival.

 

[hivoltage]

The load has no difference in the shock....unless you are in series with it. For Instance, you have a load disconnected and you grab both wires. In that case you dont even have to be grounded, you are like the element in a light bulb...part of the load if I am thinking right.

 

[ELA]

Is the severity of a shock ever depend on the load?

No, but the severity of the shock can influence the size of the load

 

[nakulak]

actually, I can see where the load could actually be beneficial (lessening) the shock if the resistance on the load was very small, but this is probably unlikely.

 

[infinity]

I remember old timers saying "don't get hung up on the neutral because the shock is worse since it's going through a load." This is false. If I'm splicing a neutral for a fixture ballast with the hot already connected and I were to get between the ballast neutral and ground the shock would be related to two loads in series (ballasts load and human body). If the ballast had a load of .2 amps the shock current would be much lower given the bodies' resistance when compared to being hung up between the hot leg and ground. Simple ohms law proves this.

 

[crossman]

I agree that a load does not increase the severity of the shock, and that is whether we are in parallel or in series with it. But as mentioned, it is a common misconception amongst electricians.

Many years ago, I was working for my EC at a small facility that had their own maintenance electrician. A particular piece of equipment that normally used about 100 amps had blown some fuses. I took my Wiggie and started doing a normal test of energized fuses by checking top of one to bottom of other, and then by going in parallel with each fuse. When I started to do the parallel check, the maint. electrician beat a retreat backwards yelling "DON"T DO IT! DON'T DO IT!"

I stepped back and said "don't do what?"

Answer was "if you go in parallel around the fuse that blew, your wiggie will complete the path for that 100 amp load, there will be 100 amps in your wiggie, and it will blow up in your hand"

I pulled him aside and taught him a bit about Ohm's Law.

 

[iwire]

I remember old timers saying "don't get hung up on the neutral because the shock is worse since it's going through a load."

I still hear that. :-?

This is false.

I agree.

If I'm splicing a neutral for a fixture ballast with the hot already connected and I were to get between the ballast neutral and ground the shock would be related to two loads in series (ballasts load and human body). If the ballast had a load of .2 amps the shock current would be much lower given the bodies' resistance when compared to being hung up between the hot leg and ground. Simple ohms law proves this.

Nice explanation. :smile:

 

[ELA]

If I'm splicing a neutral for a fixture ballast with the hot already connected and I were to get between the ballast neutral and ground the shock would be related to two loads in series (ballasts load and human body). If the ballast had a load of .2 amps the shock current would be much lower given the bodies' resistance when compared to being hung up between the hot leg and ground. Simple ohms law proves this.

Simple ohms law?
Things can always get more complicated. It is true that if the series resistance (compared to the bodys) is high enough it will limit the current.
I am not so sure the ballast or transformer primary in series with a body is the best example.
If you had 120v/0.2A = 600 ohms in series with your body it would limit the current. But is the transformer primary 600 ohms at the instant it is energized?

The transformer primary may carry 0.2 amps due to the secondary loading, but isn't the primary coil impedance likely to be much lower than 600 ohms when first energized and thus not so likely to limit the current as much if your body was in series with it?

Think about inrush when a transformer is first energized. The impedance is much lower for a short while.

Seems to me an inductive load in series with your body may be a little more complex than it may first seem to be.

 

[iwire]

No matter how complicated we want to make it, a shock through another load will be less intense then a shock without the other load.

 

[ELA]

Its not a matter of wanting to make it more complicated. Simply stating that "it is" more complicated and It can be dangerous to over simplify things.
I find no comfort in having an undefined impedance in series with my body.