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In high school (and almost all the youtube videos), we are often taught that charging by induction (with grounding) requires us to first bring a positively-charged rod near a neutral conductor, and then touch the OPPOSITE side of the conductor with a ground wire. Removing the ground wire and then the charged rod will cause the conductor to be negatively-charged.

The explanation for why this works hinges on the fact that we need to touch the OPPOSITE side of the conductor so that electrons will be attracted from the ground up to that side of the conductor to make that side neutral.

By this explanation, it would mean that if we were to attach the ground wire on the SAME side as the charged rod, electrons will flow down to the ground. But in actual case, where exactly the ground wire touches the conductor does not matter and electrons will still flow up regardless.

I don't really need an explanation as to why this is the case because I understand that it has something to do with electric potential; instead, I hope to know if there is any way to reconcile these two seemingly contradictory explanations. If not, can I get some sort of confirmation that any reasoning that appeals to neutralizing the OPPOSITE side of the conductor is flat out wrong?

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    $\begingroup$ Youtube is probably not a great place to learn physics. At least in my opinion, it is so much faster and easier just to read a textbook. Video is not always the ideal medium. $\endgroup$
    – hft
    Commented Dec 16, 2022 at 18:54
  • $\begingroup$ A pretty well-regarded textbook "University Physics with Modern Physics by Young & Freedman" was also alluding to this in Chapter 21.2. But either way, you are simply missing the point of my question. $\endgroup$
    – Tham
    Commented Dec 16, 2022 at 19:04
  • $\begingroup$ "Lacks clarity"? The question seems crystal clear to me – and an excellent conceptual question! $\endgroup$ Commented Dec 16, 2022 at 20:00
  • $\begingroup$ The question seems to be: "I hope to know if there is any way to reconcile these two seemingly contradictory explanations. If not, can I get some sort of confirmation that any reasoning that appeals to neutralizing the OPPOSITE side of the conductor is flat out wrong?" If that is clear to you then vote to reopen, @PhilipWood $\endgroup$
    – hft
    Commented Dec 16, 2022 at 21:16
  • $\begingroup$ OP, does the answer provided by @PhilipWood address your question? $\endgroup$
    – hft
    Commented Dec 16, 2022 at 21:19

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The explanation that it is positive charge on the far side of the conductor that makes electrons flow up the ground wire is wrong because it ignores other charges in the set-up. In particular it ignores the prime mover, namely the positively charged rod. This will drag electrons up from the ground wherever on the conducting object the ground wire touches. The elegant way to see this is to realise that the rod raises the potential of the conducting body – which you understand.

[The displaced charges on the conducting body before the wire is applied do have a role. They move until the resultant of their fields and the rod's field is zero everywhere in the conducting body, so the free electrons stop moving. The potential of the body is therefore the same throughout.]

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  • $\begingroup$ Thank you, sir. The confirmation in your answer cuts right at the heart of what I was unsure about. $\endgroup$
    – Tham
    Commented Dec 17, 2022 at 5:36

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