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So I am preparing for an exam with material from openstax books on physics. There in the static electricity chapter I saw this paragraph,

"Because the fundamental positive and negative units of charge are carried on protons and electrons, we would expect that the total charge cannot change in any system that we define. In other words, although we might be able to move charge around, we cannot create or destroy it. This should be true provided that we do not create or destroy protons or electrons in our system. In the twentieth century, however, scientists learned how to create and destroy electrons and protons, but they found that charge is still conserved. Many experiments and solid theoretical arguments have elevated this idea to the status of a law. The law of conservation of charge says that electrical charge cannot be created or destroyed."

Since we destroyed charges, how then is it still conserved? Could someone please explain?

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    $\begingroup$ Electrons have charge $-e$, and protons have charge $+e$. As long as an equal number of electrons and protons are destroyed in a given process then the total charge will not change. $\endgroup$
    – Er Jio
    Commented Nov 14, 2023 at 18:32
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    $\begingroup$ Can you think of an example where the total charge of a system changes? $\endgroup$
    – RC_23
    Commented Nov 14, 2023 at 18:38
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    $\begingroup$ In your quote " but they found that charge is still conserved Many experiments and solid theoretical arguments have elevated this idea to the status of a law". Laws are axioms for theories of physics, they develop from experimental evidence and relate the mathematics of a theory to the observations and measurements. even when protons interact and may be destroyed the total charge goes to the particles coming out from the interaction so that total charge is always conserved. $\endgroup$
    – anna v
    Commented Nov 14, 2023 at 18:40
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    $\begingroup$ When an electron is destroyed via annihilation with a positron, the positively-charged positron gets destroyed too. When a proton gets destroyed via annihilation with an antiproton, the negatively-charged antiproton gets destroyed too. If you know what Feynman diagrams are, charge is conserved at every single vertex. (The vertices represent the fundamental interactions of elementary particles.) $\endgroup$
    – Ghoster
    Commented Nov 14, 2023 at 18:49
  • $\begingroup$ @ErJio I see, it all boils down to the imbalance only and not the actual numbers of either charge. $\endgroup$
    – Swastik 34
    Commented Nov 15, 2023 at 5:55

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The law of conservation of charge says that electrical charge cannot be created or destroyed.

I think this is a confusing way of describing charge conservation. The law of conservation of charge says that the total electrical charge (positive charges minus negative charges) is the same after a reaction as it was before. It does not say that individual charged particles cannot be created or destroyed.

An electron is created in beta decay, but at the same time a neutron changes into a proton (and a neutrino with no charge is also created) - so total charge is conserved.

An electron can be destroyed by annihilation with a positron - but the positron has one unit of positive charge, so once again total charge is conserved.

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  • $\begingroup$ Thank you, I should have searched about the other subatomic particles as well since there are other charge carriers too.... $\endgroup$
    – Swastik 34
    Commented Nov 15, 2023 at 5:53

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