Why am I not dead after repeatedly touching a high-voltage source?

Question

While playing with mosquito racket in my home, I unscrewed the racket and touched the 2 wires with my hands. I felt that my bones were dislocated, I got shocked, but I am not dead.

My calculations say that I should die:

the output voltage is 5 kV to 10 kV, my body resistance is approx. 50 kΩ, the current through my body is 0.1 A if 5 kV to 0.2 A if 10 kV.

According to the table at https://www.physics.ohio-state.edu/~p616/safety/fatal_current.html I should die; I tried this many times but I am still alive.

I think my interpretation regarding current, voltage and my body resistance is wrong (if right I would be dead by now) - please tell me why I am not dead?

Answer 1

The circuit is not quite as you have described. As stated in the comments (amongst the sea of humor), is that a bug zapper is not an ideal voltage source. It can't deliver very much power, even though the voltage is high.

You can consider the circuit more like this:

^{simulate this circuit – Schematic created using CircuitLab}

(values are guestimates).

The net result is you will get an initial current spike of maybe a few 10's of milliamps, but only for a few microseconds. After that the bug zapper simply cannot sustain the current, and so the terminal voltage will drop, and the current will most likely end up being less than a milliamp.

It's not the peak current that kills you, but a current sustained long enough to deliver enough energy to kill you.

As to why it kills the bugs, that is simply a case of bugs being smaller than you. It will take far less energy to cook a small bug than it will to stop a human heart.

Answer 2

• Passing the current through a finger is relatively safe, as there is not enough current to burn you, and it's far from your heart.

• Passing the current from hand to hand puts the heart somewhere "in the middle" of the path, but clearly not in direct series. Plus your skin can still present a large resistance.

• If you pass the current across your chest, the chance of death is higher.

• If you had probes that went deep into your chest, and passed the current through the probes, you'd dramatically increase the risk.

As others have stated: The bug zapper has a very limited amount of power that it can deliver. There is enough energy to fibrillate a bare heart, but yours is protected in your body.

Answer 3

To put this more like an electrical engineer would put it: this high-voltage source has a high internal resistance, and understanding what that means answers your question.

Answer 4

It is not only current and voltage that matter, but duration. 10kV at 1A for a microsecond is about 10 microjoules. You might feel a shock, but it is not enough to actually tense all your heart muscles into paralysis long enough to make you unconscious, or even cause physical damage from heating or muscle contraction.

On the other hand, IF you have a bad heart it might be enough to upset the rhythm and send you heart into fibrillation, which can be fatal. Maybe you are just lucky

Answer 5

Death from electrocution occurs mainly in two situations and is not directly correlated with the actual current/voltage values:

1) Enough current and energy passed through your body to actually burn you inside out 2) A voltage passed through your heart and put you into a fibrillation state.

Both can come into play at the same time!

The first is mainly caused by excessive current into your body. Once the skin is penetrated, it is easy to pass a surprisingly high current into your body. This is why wet + electricity is so bad. It reduce drastically your skin resistance.

Before venturing into the 2nd part, you need also to understand that electricity will have an entry point and an exit point. You can often see a burnt mark at those points when it occurs (in hard situation).

Directly related to that: if the current pass through your heart with a voltage high enough or with some weird frequency, it can put your heart into fibrillation: desync it. When this occurs, you need to reset your heart using a defibrillator like in all poorly written medical drama. A shock does not so much when the heart is flat-lining, but help fibrillation cases.

As for your question, you didn't die because the current entered finger and exited through your finger. It didn't pass through your heart. Also, the current in play we're not enough to cause any significant burns. Specific injuries prediction is on a case by case basis.

In a nutshell, your heart either fail or you burn to death when you die from an electric shock...you might also survive and be severely burnt or maimed by the aftermath. Losing limb is unfortunately not so uncommon.

If you want to know more, the wikipedia article is well written.

Answer 6

Another aspect to consider is frequency. Mosquito zappers are DC, but they don't supply constant DC. After the voltage is stepped up from 3-6 VDC from the batteries through a voltage multiplier, it comes out in rapid pulses. As soon as voltage is applied and your body begins to take the energy, the current is stopped. I don't know exactly at what frequency mosquito zappers operate, but at high enough frequencies, the human body can simply absorb the shock in the skin before it reaches deeper into the nervous system and your heart. That's why you're able to be shocked by a tesla coil without dying. You still feel it, but it doesn't penetrate far before the pulse ends and simply dissipates before the next pulse comes along.