Posted By Alan Hoskins The potential for a shock would depend on the resistance of the person's body. Even at lower voltages, if the body resistance is low enough (usually because the skin is wet) a shock could occur. (nine volt battery on the tongue produces an electric shock, though not harmful, and there are urban myths surrounding this practice). Whether such a shock would be damaging or even fatal would depend on the circumstances, but remember that when a person receives a shock they might jump back and be injured from another source. Alan

Posted By Garry Homer DC is more difficult to let go but contact with a conductor at 70V does not describe the situation in sufficient detail for anyone to provide a substantial answer. Is the dc source referenced to earth by some connection? How many conductors can you touch simultaneously? What is their separation? What is the source of the dc? What limits the current to 100A? Garry

Posted By Jason Touraine The effect of coming into contact with a live conductor depends on how much current flows through the body and for how long. Is the 70 V conductor referenced to earth or to another conductor? If the former, then we would normally be looking at a flow of current through the feet to earth; if the latter from say a hand touching one conductor to hand touching the other conductor. To work out how much current we need to go back to ohms law. The current depends on the voltage divided by the resistance. The resistance of human bodies varies considerably between individuals and indeed during the day for an individual. The resistance of a person with dry hands might be about 10,000 ohms (although it could be much higher) but with sweaty hands it would probably be about 1000 ohms. The IEE suggest using 500 ohms to be used as a sensible worst-case). So with a 70 volt source we could expect a current of 7 mA with dry hands and 70 mA with wet (or 140 mA using the worst-case suggested by IEE). The so-called "let go" current for DC is about 70 or 80 mA for a 70 kg person (for AC it is much lower -- around 15 mA). (It should be noted that these figures are not universally accepted and some suggest much lower currents and it does depend on a number of factors such as body weight). Of course, if the current flow is through the feet to earth it would not be normal to have bare feet in the workplace so the resistance would be considerably higher with normal footwear and possibly high resistance flooring material. A DC current of 7 mA would probably be perceived by most people. Ventricular fibrillation would normally require several hundred volts DC (much lower with AC) but is strongly dependent on duration and some suggest much lower figures are used.

Posted By Jason Touraine Yes, it doesn't to very high voltage either. I still remember sticking a paper clip in a landrover 12 volt power supply on the dash board when I was about 10! Mainly because of the reaction of the driver!