The core, the nucleus, of an atom consists of positively charged protons and of neutrons that do not have any charge. The nucleus in its entirety is considered to be positively charged. Surrounding the atomic nucleus is a cloud of electrons. Electrons are negatively charged. If the number of electrons are the same as the number of protons, then the atom is electrically neutral. There is electric equilibrium.
Source: https://www.sciencefacts.net/atom-2.html (2026-08-31)
This equilibrium can change. This happens when the number of electrons is unequal to the number of protons. The atom is then called an ion. If there are more electrons than protons, the ion is negatively charged. If there are less electrons than protons, the ion is positivley charged.
Source: https://sciencenotes.org/what-is-the-difference-between-an-atom-and-an-ion/ (2026-08-31)
Any object or material that contains ions is no longer electrically neutral. It has an electric charge or “potential”. Between to differently charged objects or materia, there is potential difference or “voltage”. This electric imbalance always wants to equalize: atoms “want to be” neutral. Ions are either going to give away or receive the amount of electrons needed to achieve this equilibrium. This happens when two differently charged objects or materia directly touch or it can happen by influence in an electric field. Until a charge is equalized it remains and is considered static.
An example of charges equalizing by direct contact is when two differently charged people touch each other and experience a shock. Or when you happen to have collected an abundance or electrons, thus creating negative ions, and then you touch a differently charged object.
Source: https://thors.com/manufacturing-courses/manufactured-products/electrical-and-electronics/electrostatic-discharge-esd-basics/ (2026-08-31)
An example of charges equalizing through electric fields is lightning striking the ground. The potential difference between clouds and the ground is so big that matter between them is ionized and finally, when the potentinal difference is big enough, the charges equalize in the form of visible current.
Source: https://www.savemyexams.com/igcse/physics/oxford-aqa/16/revision-notes/electricity-and-magnetism/electrical-circuits/static-electricity/ (2026-08-31)
Another example is dust particles being pulled towards oppositely charged electric devices in your home. Or styrofoam on a cat.
Source: https://commons.wikimedia.org/w/index.php?curid=60287175 (2026-08-31)
To be continued. Meanwhile, some questions that popped up:
- What determines the amount of voltage needed for a current to discharge in a scenario where the opposite charges never touch but only ever interact through the electric field? Some assumptions of mine: distance to each other, (air) humidity, medium (air, vacuum, other), resistance, interference from other electromagnetic waves…?
- What creates ions, except for the above mentioned physical friction? What natural phenomenon or scenarios kick electrons off or shoves them onto atoms? Is this what we artificially do in batteries? Creating negative and positive ions to create voltage?