Um, please note that electric shocks where the current path is through your chest CAN KILL YOU. If a big pulse of current hits your heart at just the right time, it will trigger a heart attack (the timing is only correct in maybe one chance out of a few hundred random attempts.) Holding hands in a chain is a great way to create a lethal current path. Also, if one person in the chain has an undiscovered heart condition, the chain-shock can expose this problem… by stopping their heart. Great party trick.
Lethality aside, I figure that you’d need around 55 people to cut the shocking current by half, and you’d need an enormous number to eliminate the shock entirely.
I had the same “flyswatter” and measured the output at only 1200 volts DC. (I was hoping for more like 10KV).
If I’m typical, then the electrical resistance of human skin for small-area electrical contact is a few hundred ohms or a couple of thousand ohms at most. Touching the 1000V power supply against a couple 500-ohm fingertips gives you pulses of one ampere. That should be REALLY painful! Even 1/1000 ampere pulses makes your muscles twitch violently.
On the other hand, the average current produced by the flyswatter can’t be one ampere (one amp at 1000V is a kilowatt after all!) So, the current will depend on the internal limitations of the power supply inside the swatter. If the device is, say, 2 watts on battery power, then when connected to a 1000-ohm patch of human skin, the current through flesh will be 45/1000 amperes (45 milliamps, which should give a very painful shock with muscle spasms.)
How long a chain before you can’t feel the shock anymore? If you form a human chain, but if you all firmly hold hands, then the fairly large area of skin contact of hands will be different than when you touch the narrow flyswatter wires with a fingertip. Holding hands gives VERY good conductivity, so adding lots more people to the chain might not reduce the level of electric current going through your muscles. Why? It’s because most of the electrical resistance is from the fingertips touching the flyswatter wires, and this determines the current and also swamps out the effect of the added electrical resistance between vast numbers of sweaty palms in contact. If the fingertips contribute 500 ohms and the hand-holding surfaces each contribute ten times more conductivity or 50 ohms, then a one-person chain would feel 45 milliamps, but ten people in series would still get 37mA (still just as painful). To cut the current in half you’d need around FIFTY people. To bring it down below the threshold of feeling (of around 1/2 milliampere) you’d need, ahem, 160,000 victims.
Important note: we’re talking SIGNALS here, not energy. 50 milliamperes current in your flesh creates a nerve signal for major pain, even though the energy involved just slightly heats the skin in contact with the wires and doesn’t heat your muscles significantly. The skin presents most of the resistance and gets most of the heating. The people holding hands in the chain wouldn’t even feel the skin heat, but they’d suffer the same pain since their nerves “hear” the same 45mA signal which whispers to their muscles “experience agony now.”
PS Include some people with very dry palms and you’d need lots fewer in your chain.