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If there is a charge in the center of a closed room, with just walls that are not charged: the electrical forces can traverse the walls, are they absorbed by the non charged walls, or are reflected back?

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Objects that are overall electrically neutral, but are made of positive and negative charges, can still interact electromagnetically. This is how wires work; even though the wire itself is not charged, it still carries current because the electrons in the wire are moving.

In the case of a wall, electromagnetic radiation impacting it interacts with the electrons on the surface of the wall. How much of the radiation is absorbed or reflected depends largely on how the electrons in the wall are allowed to move. If the electrons can move freely (as in most conductors), the radiation is mostly reflected. If the electrons' motion is restricted (as in most insulators), the radiation is mostly absorbed (if it roughly corresponds to an allowed transition between electron energy bands) or transmitted (if it does not).

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  • $\begingroup$ Why it is absorbed or reflected? "if it roughly corresponds to an allowed transition between electron energy bands". To understand this statement do I need to study quantum mechanics? $\endgroup$ Commented Nov 13, 2018 at 16:10
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    $\begingroup$ A metal wire is not charged in the sense that it is electrically neutral (equal number of protons and electrons), but they have free electrons (mobile charge carriers) that can readily move when an electric field (voltage) is applied, which is why they are good conductors. For metal conductors electrons move, but not the protons. $\endgroup$
    – Bob D
    Commented Nov 13, 2018 at 18:33

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