Science Technology
What Hurts More, AC or DC?

Everyone’s favorite engineer Mehdi Sadaghdar is back with a tongue curling look at what current hurts more…

Remember kids, always make sure to check the voltage before subjecting yourself to pain like this. Or better yet, leave it to the professionals.

32 thoughts on “What Hurts More, AC or DC?

  1. “Remember kids, always make sure to check the voltage before subjecting yourself to pain like this.”
    Current is the killer – anything over 70 MA going directly through the heart can cause de-fibrillation and possibly death
    I would not recommend doing this at home with an ordinary hobbyist power supply – the power supplies in the above video probably have adjustable current limitation. Your average hobbyist supply doesn’t have current limiting other than a fuse or circuit breaker.

    1. It absolutely is, but remember that you are also a giant resistor. And since voltage, current, and resistance are all intimately related, “check the voltage before subjecting yourself to pain like this” is still valid.

      1. The relation is

        Current = Potential Difference / Resistance (http://en.wikipedia.org/wiki/Ohm's_law)

        But that is still not all of the story, because every power source has a limit on how much current it can actually provide. Which is why you see in your laptop’s power adaptor a statement of how much current it can actually serve.

        For instance, if you short a single 9V battery, the voltage is going to go down very quickly, simply because the battery itself cannot provide as much current as the short would ask for (if a short circuit approaches near zero resistance, it would ask for near infinity current). In the video he power transformers attached to the outlet, which are most likely capable of getting something in the range of 10A.

        That’s why his experiment is *way* more dangerous than taking two 9V batteries in series and putting in your tongue.

    2. The problem isn’t that the current causes defibrillation, it’s that it cause fibrillation. Defibrillation is a whole ‘nother complicated topic. Be careful with either, but go take that CPR course from the fire department and learn how to use an automatic defibrillator. You never know when you might have the opportunity to discharge a very big capacitor into someone’s chest–and have him or her thank you for it later!–David Kazdan, MD

  2. When I used to repair CRTs, the old guys would tell you to put one hand behind your back when you discharged the tube. The idea was to keep from the current from going through your heart.

    1. Another trick I heard was to touch things with the back of your hand so if you got shocked, your muscles would contract and pull your hand away from the circuit.

      1. I whacked myself in the face trying to find a cold solder joint by tapping the backlight inverter on a laptop one time. The solder joint was hot and burned through the mylar “warning high voltage” protector. But the few times I’ve got bit really bad, my arm pulled away from the circuit. I’ve seen people’s muscles lock up from high voltage (not pretty) so I the back of the hand thing makes sense, if only for the insulating properties of fingernails.

  3. This guy is delightful! (right down to the political quips) sometimes acting dumb is the best safety warning/example …and it’s funny, so it’s memorable. he deserves his own Make(zine) “tag”.

  4. I’ve been hit with 200 – 300 volts AC & DC and can tell you it doesn’t matter, they both hurt. It’s happened at least 10 times over the past 10 years.

  5. Besides DC and line AC power, you should add RF shocks. Try touching a CB or ham antenna in the right place when they’re transmitting. The RF energy travels is and confined to the surface of your skin, where all the pain receptors are. Nerve cells generate pulses, i.e. AC signals, to boot. The RF super-stimulates them. The pain is so intense it makes licking a power cord feel like drinking a nice cup of hot chocolate.

  6. RF burns HURT!! I found out the hard way while working inside the tailboom of a helicopter on an antenna mount when another tech thought he would play a joke on me. Lemme tell you, there is nothing like being inside what amounted to a sardine can, with nowhere to go and feeling the intense heat in your hand. Because of the close quarters, I couldn’t have let go if I wanted to!

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