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Since electromagnetic induction (faraday's law) is described as inducing a current why then would you need to be grounded to receive an electric shock? Since current is already present?

If say (use your imagination) a giant copper coil being spun in a magnetic field (an AC generator) was floating in the air, and had small copper lead attached also floating in the air, and then you were holding onto this (you are also floating) would you not get fried by the induced current? If the magnetic field and spin were fast and strong enough?

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It is technically true that very intense magnetic fields can do awful things to a human brain, but what you're asking about is current flow. In your example there is no return path for current flow, the circuit is not complete, and you are safe. If there was a second lead that could complete the circuit, then current could flow.

Of course, I should point out that if your example creates an extreme voltage, the path could possibly complete itself, through the air, in the form of an arc. Also, don't go thinking you can just put on thick rubber shoes and grab a high voltage line - the rubber forms a kind of capacitance, through which a lethal AC current can still flow to ground.

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  • \$\begingroup\$ That was pretty much my realm of thinking. By completing the circuit then you mean if the person was touching the lead and was footed to the earth? \$\endgroup\$ – user40262 May 10 '14 at 2:35
  • \$\begingroup\$ It has to have a complete circuit, from out of the high potential, through you, to ground, then back to the generator. In a real life situation, generators are already grounded on their wye point, making it easy. Some installations aren't grounded, but it will go through the conductor insulation, similar to the shoes example I used. There is no inherent danger in being charged up to a voltage, just when charge flows. \$\endgroup\$ – Sean Boddy May 10 '14 at 2:40
  • \$\begingroup\$ In practice, ground need not be involved at all. If you touch both ends of an ungrounded high voltage supply, you will get a shock (or worse). Ground does get involved in most shock/electrocution incidents because one side of the AC power distribution system is grounded, so touching a live wire and ground will complete a circuit. \$\endgroup\$ – Peter Bennett May 10 '14 at 6:42
  • \$\begingroup\$ The AC distribution system is grounded I presume so that the current flows to the lowest potential while making it's way around the distribution grid? \$\endgroup\$ – user40262 May 10 '14 at 15:11
  • \$\begingroup\$ Nope. Grounding provides a discharge path for lightning strikes and DC voltages created by other phenomena, and simplifies the detection and clearing of shorted lines. \$\endgroup\$ – Sean Boddy May 10 '14 at 15:43

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