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It seems to me that every time there happens an electric shock through the contact with the ground, it happens because there is a difference of potentials between the contact point and the ground (for example touching a live (hot) wire,) and also because the body completes the circuit with a grounding rod to which the neutral (or ground) wire is connected. It seems that if there was no rod in the ground (no grounding) there wouldn't be a way for this current to have a complete circuit. Thus, you can touch wires of an isolated circuit and never get an electric shock because the current will never find a way back to the circuit.

Do we need to bother then to ground isolated circuits? For example, a car is not grounded, and you don't get a shock from touching a single battery terminal. Of course a car battery of 12V will not kill you anyways. If it had a potentially dangerous voltage would people try to ground things like cars?

Does the grounding have something to do with things connected to the common electrical grid (like power stations) where the electric energy has to be shared with everybody?

JRE
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CHILLQQ
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  • It's because earth ground is 0V and it's like an infinite sink because the earth is so big. If you touch something at ground you will also be 0V, if you get shocked it's because you were not 0V. – Voltage Spike Jun 13 '22 at 15:34

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If you ever got ESD-zapped by a car, you’ll wish it had a functioning grounding strap or conductive tires.

Grounding is there, among other things, to get rid of the possibility that something you touch is not at a ground potential. For example, I can be tossing electrically charged spheres to you. Literally metal balls. Each time you catch one, you get zapped. If you picked them up from the ground instead, they’d be equipotential to ground and thus safely discharged.

Ungrounded metal poles and towers are bad news due to potential for atmospheric discharges – if the tower is not grounded, you become the grounding conductor when you touch it. Same goes for a possibility of overhead power lines coming into contact with the ungrounded structure.

Grounding for safety is done any time there’s a reasonable likelihood that the conductive objects you come into contact with may be at a dangerous potential relative to earth due to either galvanic connection only charge accumulation.

Kuba hasn't forgotten Monica
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  • Grounding the car to earth makes little difference, if your shoes isolate you from earth, and your clothes charge you up. The charges still equalize with a zap when you touch the car. – Justme Jun 13 '22 at 09:27
  • Thank you for your answer. Curious about the spheres part: if I hold a charged sphere there is certainly a potential difference so the current would flow if there was a path to complete that circuit, but there isn't really. So why would I get zapped ? I am thinking about electrical fence for instance. It is under a noticeable voltage, and yet it relies on metal rods stuck into the ground in order to complete the circuit and give one a shock. Stay on an insulating chair and you can touch this fence all you want. (rather good illustration https://www.youtube.com/watch?v=hQKqXNkf4Fo) – CHILLQQ Jun 13 '22 at 13:16
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The main reason we ground stuff is earlier fault detection. Meaning if something is wrong with your appliance and its frame goes live it triggers whatever safety mechanism you have locally wihtout you needing to touch it.

Yes if you are isolated AND you touch an isolated circuit not much will happen. However in reality you will almost never be well isolated and rarely be in reach of only one appliance at once. Hence why things need to be grounded to a common level. Just walking barefood in your kitchen can make you conductive enough to receive a very real shock from mains.

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