Re: Electrify Vehicle Body?

Would a spark plug's voltage (~20kV) kill you if its duration were sufficiently long?

In other words, is spark plug voltage non-lethal /only/ because it's present for just a few milliseconds?

Let me rephrase that.

In other words, does a spark plug's voltage have little likelihood of causing injury solely due to its short duration?

There are several factors in this case. Yes, the duration is reasonably short, second the spark is actually of an oscillatory nature (high frequency AC), and third, there is resistance built into the circuit. If we are talking about the spark plug itself, with no human present, the resistance in the system is not a factor while the voltage is building up across the gap, only after the spark fires. If a human touches the terminal, the resistance to ground is very much less than across the gap, so the resistance in the wires draws down the voltage quickly, so the initial pulse is a very high voltage only for a very short time, then falls to a considerably lower value.

What I do not know is whether this resistance and capacitance to ground through the human is sufficiently low to damp the oscillations in the circuit. That is, when it flows through a human, is the current sufficiently damped that it is not oscillatory? If it is still oscillatory, the HF nature exhibits a skin effect, and does not penetrate conducting bodies very well.

BTW, the oscillatory nature of the spark, in the HF range, is why we get ignition interference in AM radios.

Its non-lethal because its extremely low CURRENT. Current flow through the heart muscle is what kills, the voltage merely pushes the current along. IF the voltage is low enough, skin is a good enough insulator that no current will flow through the body, even if the current source can provide a ton of current (example: a car battery can easily supply several hundred amps, but the 12 volts can't overcome the resistance of your skin so you can handle it all day). Conversely, you can also be exposed to huge voltages without harm PROVIDED that the source is limited to tiny, tiny currents (example: scuffing your feet on the carpet and then touching a doorknob, ignition coils, toy Van de Graaf generators, etc.) Things get deadly when there is sufficient voltage to push current across the skin barrier, AND the source can deliver enough current to cause harm.

Duration does matter. You can survive a very short pulse of a voltage and current that would be deadly if sustained, because nerve cells require a finite amount of time to polarize or de-polarize since it is a chemical process at work (controlled ion diffusion across the cell membrane). If a short pulse of current flows through a nerve or heart muscle and is sufficiently short that the nerve and muscle tissue can't respond, nothing happens. However, short pulses can still cause burn injuries at the site where you're exposed to the source.

not true. You can create electron flow by simply changing the shape of your surface.

What do you think happens when your drag your feet on the carpet and touch the door know. What are you calling the circuit in this case?

I can't believe you have an EE degree. Impossible.

Lg

Yes. Also, the technique used to increase the voltage from 12 to thousands is only capable of delivering a small burst of current. Of course it does hurt, so I'd hardly want to experience more than one hit.

Now I know for sure you don't know what you are talking about. You do not have any science or engineering degrees. My part of the conversation has ended.

I actually have two, one is a masters. But I don't have any in teaching...

You part has been increasingly to attack my education as opposed to my information. Can't say you contributed much to the conversation outside of that.

People seem anxious to throw dirt on folks and demean them in this group. When you and other folks don't understand what I am talking about you start attacking my education?

Even the EE that disagreed with me had to insult me.

I in fact have 2 degrees, 1 in electrical engineering and 1 in computer engineering, but unfortunately none in teaching.

This whole topic Gauss law. However, the mathematics is quite complicated. I thought I could relay the concept through simple examples.

I ask simple question but nobody answers.

Please explain where you think the circuit path is when you drag your feet across a carpet and touch a door knob?

What happens to the surface charges when two like-charged balloons are brought in close proximity to each other?

If you understand Gauss law, then you should understand that you can change the surface of a charged object and the charges will _redistribute_. Surface charge distribution on sphere is different from a cube is different from a pole, etc. When charges move what do we call that?