I was watching a fascinating video about the people who work on live power lines- they are lifted to them by helicopter and wear metal-fabric jumpsuits in order to create a Faraday cage around their bodies so they can work on the live wires without getting shocked. But then I started thinking about voltage in general- do they really need to wear the suit? All of the simplified examples that are used to explain current talk about the grounding effect- a current is created between a voltage source and the ground since the ground has a voltage of 0V. But if the worker accesses it by helicopter, he doesn't have that voltage difference, so a current shouldn't run through him anyways (bird on a wire don't need a metal jumpsuit!) But then, what is the voltage of a person who approaches a live wire (or a van der graaff generator, or a socket, or anything with charge?) The demos always show that a person who is insulated from the ground can touch the charged object (at least for the examples I've seen when it doesn't have a huge amount of charge- like a Van der Graaff generator) - but the person must have SOME voltage difference, or else we would be walking around holding 20,000V! But it's not 0V, because as long as the person is insulated they don't get shocked, the charges just collect around them (the typical hair standing on end.) So my questions: Is the faraday suit really necessary? And what is the voltage of a person insulated from the ground?