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Electrostatics is a branch of physics that studies electric charges at rest.

Since classical physics, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amber, ήλεκτρον, or electron, was thus the source of the word 'electricity'. Electrostatic phenomena arise from the forces that electric charges exert on each other. Such forces are described by Coulomb's law. Even though electrostatically induced forces seem to be rather weak, some electrostatic forces such as the one between an electron and a proton, that together make up a hydrogen atom, is about 36 orders of magnitude stronger than the gravitational force acting between them.

There are many examples of electrostatic phenomena, from those as simple as the attraction of the plastic wrap to one's hand after it is removed from a package to the apparently spontaneous explosion of grain silos, the damage of electronic components during manufacturing, and photocopier & laser printer operation. Electrostatics involves the buildup of charge on the surface of objects due to contact with other surfaces. Although charge exchange happens whenever any two surfaces contact and separate, the effects of charge exchange are usually only noticed when at least one of the surfaces has a high resistance to electrical flow. This is because the charges that transfer are trapped there for a time long enough for their effects to be observed. These charges then remain on the object until they either bleed off to ground or are quickly neutralized by a discharge: e.g., the familiar phenomenon of a static "shock" is caused by the neutralization of charge built up in the body from contact with insulated surfaces.

Coulomb's law

Coulomb's law states that:

'The magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.'

The force is along the straight line joining them. If the two charges have the same sign, the electrostatic force between them is repulsive; if they have different signs, the force between them is attractive.

If is the distance (in meters) between two charges, then the force (in newtons) between two point charges and (in coulombs) is:

where ε0 is the vacuum permittivity, or permittivity of free space:[1]

The SI units of ε0 are equivalently  A2s4 kg−1m−3 or C2N−1m−2 or F m−1. Coulomb's constant is:

A single proton has a charge of e, and the electron has a charge of −e, where,

These physical constants0, k0, e) are currently defined so that ε0 and k0 are exactly defined, and e is a measured quantity.

Electric field ε 0 q Q r 2 = k 0 q Q r is the distance (in meters) between two charges, then the force (in newtons) between two point charges and (in coulombs) is:

where ε0 is the vacuum permittivity, or permittivity of free space:[1]