Can Electricity Kill You?

Well duh! But not all electricity is harmful, or is it?!

Well, I guess it could hurt even when it is not too dangerous, so be careful!

But how can electricity be harmful? In low levels, if it passed through your heart or your brain, it can leave damage or death. They say 5mA of current through the heart can cause a cardiac arrest. In high levels, it can badly burn the body inside and out and then possibly cause death.

So electricity is dangerous, but not always. When something is capable of delivering many amps of current, it doesn’t necessarily mean that it will hurt you. Remember:

Short Circuit Sparks
Voltage = Current x Resistance

So you need high voltage to generate high current. For DC currents, the body resistance through dry skin is usually pretty high, in orders of 100 kilo Ohms. So to create 5mA of current, you will need somewhere over 500VDC. And even then, you need to touch the voltage in a way that the current actually passes through your sensitive parts, I mean your heart for example. You can barley feel a 100V DC through dry skin.

Of course when the skin is wet the resistance drops significantly and lower voltage can hurt too. The tong is a low resistance part of the body. Have you ever put a 9V battery on your tong and see how that hurts? No?? Then you should try it! Don’t worry, this one is safe!

It is very different for an AC current. Human body has a capacitive property, which means as the frequency goes higher it shows smaller resistance towards current and more flows with less voltage amplitude. While you don’t feel anything for a 50VDC voltage, you can badly hurt with a 50VAC, 50 Hertz.

As a crazy engineer, I have touched many different kind of electricity, of course not for fun, but in the line of duty! Please don’t try it yourself and just go with my experience.

– I once made a DC voltage generator and raised its voltage up to 600V slowly and held the wires. It is unbearable at around 300V!

– I have touched 220VAC (European standard, 50Hz) and 110VAC (North American standard, 60Hz) many times and I should say they both hurt pretty much the same. I am guessing 110VAC hurts the same as 220VAC because of its slightly higher frequency. Of course I can’t say I am an accurate hurting scale.

– I have been zapped many times with ESD (Electrostatic Discharge) voltages of between 0V to 25KV. The 25KV stings badly.

– I have touched the ringing voltage on the phone lines. If memory serves right it is 90VAC at 25Hz. It hurts a bit.

Here’s my favorite frame of the video when sparks are hitting my face!

Short Circuit Sparks

8 thoughts on “Can Electricity Kill You?

  1. What is your opinion about these mad-crazed race events which now advertise obstacles with 10,000 V? I assume the source involves a DC based capacitance discharge (extremely short). You hear many people saying that it is current that kills, but obviously they are insane. Thoughts on this? How does time relate to this equation?

    • if the high voltage is present for very short time, less than micro seconds, then it is relatively safe. You know, when you touch a door knob and zap yourself, the voltage could be anywhere between 8kV to 12kV. When you slide down plexiglass slides held by metal screws, you can zap your butt with 25kV! The current is still huge, but the time duration is very small and so the energy is very limited and can’t make a damage.

  2. First of all, thank you! You make excellent points, and you’re very funny doing it – always a great combination. Safety instruction never seems to stick unless you actually see what can go wrong, going wrong… I have to say that watching your videos (especially the exploding capacitor) makes me cringe because you’re not wearing eye protection. Please don’t maim yourself for our enjoyment!

    On the subject of 9 volt batteries: you can definitely kill yourself with one, if you go out of your way to be stupid!

    Please don’t make a video demonstrating this.

    • Thanks for the comment. I agree with what you say. The only issue is that just re,moving your skin and putting a 9V on it won’t hurt the heart. Your 9V line must go on the sides of the heart so that the current flows through the heart. If the probes go that deep, you already have other issues too! The human tong is much lower resistance too, and if you put the 9V battery on it you will definitely feel it (I’ve done it before). But it is not going to kill your brain as the current doesn’t get there.
      And don’t worry, I’m not going to hurt myself on purpose!

      • My understanding was that – since current follows the path of least resistance – when he pierced his thumbs, the current path was up the inside of each arm and across the chest. The resulting shock probably didn’t stop his heart: it didn’t need to. All of the chambers of the heart have to work in fairly close synchronization to pump blood, otherwise it’s just wasted motion; the timing signals that keep things in sync are very low voltage and extremely low current; the shock probably bumped him out of sinus rhythm into fibrillation.

        As for the tongue, I have to admit that not only have I never considered it particularly harmful – it’s my standard check (if I don’t have a battery tester handy) to see whether a 9V is still good. If I feel nothing, or if it just barely prickles, I toss the battery; if it hurts like hell, the battery is good.

  3. Thanks for blowing your self up for our amusement! I hope you don’t end up on the airplane watch list. Be safe and more importantly… be funny (you are, thanks)!

  4. Pingback: Don’t worry, it’s just ESD! (Electrostatic Discharge) « adafruit industries blog

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