Przypomnienie wiadomości na temat zasady zachowania ładunku

A neutral object can become negatively charged when electrons get transferred from another object (see Figure 1).

In Figure 1, a negatively charged conducting rod with net charge $-4e$‍ touches a neutral conducting sphere. During the transfer, $2$‍ electrons move from the rod to the sphere because the electrons are repulsed from each other and want to spread out. Afterward, the rod has a net charge of $-2e$‍ and the sphere has a net charge of $-2e$‍.

The total charge between the two objects is $-4e$‍ before and after the transfer, so charge is conserved. The electrons redistribute so the rod becomes less negatively charged and the sphere becomes negatively charged.

A neutral object can become positively charged when electrons get transferred to another object (see Figure 2).

In Figure 2, a positively charged conducting rod with net charge $+4e$‍ touches a neutral conducting sphere. During the transfer, $2$‍ electrons move from the neutral sphere to the rod because the electrons are attracted to the positive charge and want to spread out from other electrons. Afterward the rod has a net charge of $+2e$‍ and the sphere has a net charge of $+2e$‍.

The total charge between the two objects is $+4e$‍ before and after transfer, so charge is conserved. The electrons redistribute so the rod becomes less positively charged and the sphere becomes positively charged, and the protons remain fixed.

People mistakenly think that an object gets positive charge by receiving extra positive charges. Protons have positive charge and are bound to the object, while electrons can be transferred between objects. When an object’s net charge becomes more positive, it has lost electrons.

For deeper explanations of conservation of charge, see our video about the law of conservation of charge.

To check your understanding and work toward mastering these concepts, check out our exercises: