A dangerous pencil hack 4


Youtube suggested I should watch this video – I couldn’t resist.

Having touched a live 240V wire by mistake was a memorable experience (I still remember it even though it was twenty years ago), so I am not too keen on trying this pencil hack out and I suggest you don’t either.

The idea is interesting, though. An explanation how this works would be nice.

Again, I don’t suggest that you try this at home (or at work, or while out and about).


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4 thoughts on “A dangerous pencil hack

  • Sapphire

    At this voltage the carbon in the pencil core is a very good conductor. Without the lamp or another resistor the short circuit formed between the live and neutral lines would just trip the circuit breaker.
    Or it just might cause a fire!
    There will be a degree of arcing as the pencil almost touches the knife blade. It seems as if it will be enough to weld the carbon into the steel, though I’m not in a hurry to try it. The point of the pencil would certainly get hot enough to melt the wax in the core but that would not make the marks permanent I would tend to go with the arc weld theory.

  • Klaus aus B.

    I agree with Sapphire’s approach: Due to the oscillating vertical movement arcs are produced. The resulting temperature – even though effective only in a tiny zone – heats up the blade’s surface in the contact area. The rapid cooling process creates carbon inclusions on the surface.
    The bulb limits the current. The results actually depend on the “dipping”-speed of the pencil point. The faster you do it the fainter it gets due to the fact that a hot bulb has a much higher resistance than a cold one.
    For reasons of safety it is not recommended to do it like in the clip. If you can’t ensure by use of a measurement device that the clamp is on N-potential you should keep your hands away from all conductive materials. At least you are supposed to use isolated pliers to hold the pencil.

  • Matthias Post author

    Thank you very much for expanding on the explanation.
    I’d love to try it out, but won’t do it as I don’t trust my clumsiness.