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From electrostatics, I learned that grounding an object will render it uncharged. However, by combining polarization and induction an object can have a net charge. This is because the electrons will move from a low potential to a high potential (towards the positive parts of the object). I understand why it happens - but then this charge is temporary. As soon as it comes into contact with another object the charges will balance out as there is an excess/shortage of electrons on that object. My question is why do most objects have a tendency to become uncharged? Is it really as simple as saying that electrons are the only moving charges and they will always move towards the positive charges meaning the net charge will become 0 as protons and electrons have the same charge magnitude? Is there a better “physics” way of explaining this tendency?

Thanks

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  • $\begingroup$ Because like charges repel each other? $\endgroup$
    – knzhou
    Commented Mar 2, 2020 at 20:11
  • $\begingroup$ What seems so "un-physics like" as a statement about the attraction/repulsion of opposite/like charges? To me that's the physics at work right there. $\endgroup$
    – Triatticus
    Commented Mar 2, 2020 at 20:18
  • $\begingroup$ It just seems weird; yes, like charges repel and opposites attract. But how do we go from here to the fact that most objects you encounter in everyday life are uncharged. Many people on this website are more experienced in this topic that I am, so if like charges repel and opposites attract is a sufficient answer then this question must be closed. $\endgroup$
    – Bandoo
    Commented Mar 2, 2020 at 23:59

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There are at least two reasons why things tend to be uncharged.

First, the atoms that make up solid matter like metal, glass or plastic are themselves uncharged, which means a large collection of them will also be uncharged. Also, in the case of ionic solids like table salt, the number of positive ions is exactly balanced by the number of negative ions in the crystal lattice and so a large chunk of that material will carry no net charge as well.

Second, although it is possible for charges to separate, move about, and accumulate via friction on the surfaces of insulators, those surfaces usually have some dirt and water molecules adsorbed onto them which render them just a tiny bit conductive. That tiny conductivity is enough to dissipate any accumulated charges.

The exception to these cases is when for example stray electric ("static") charges accumulate on an object which is electrically connected to a capacitor which is capable of storing electric charge for long periods of time without dissipation. A capacitor bank mounted in a trailer with rubber tires and left in the wind under low-humidity conditions can store enough charge to kill a human who touches the master "hot" terminal and the ground line at the same time. The RC time constant in such a system guarantees that the unfortunate human dies exponentially.

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