The electrification is a process by which a body gains or loses electrical charges.


Electrified Bodies
Are those with excess or lack of electrons, so that:
  • A body is positively electrified \(\implies\) number of electrons \(\lt\) number of protons
  • A body is negatively electrified \(\implies\) number of electrons \(\gt\) number of protons
  • A neutral bodie \(\implies\) number of electrons \(=\) number of protons.
Conductors and Insulators
Conductors are materials that easily conduct electric current. Insulators are materials that offer extreme resistance to the electrical current.

Types of Electrification

Frictional Electrification
Whenever we rub two initially neutral bodies, they get electrified with charges of opposite sign. The material which has weakly bound electrons will give them to the other body, leaving a net positive charge. In contrast, the other body will be left with a net negative charge.
Frictional electrification scheme. First, we have two neutral objects (glass and wool), i.e., with equal numbers of positive and negative charges. Glass transfers negative charges when rubbed against wool. As a result, we have two charged bodies: the glass with positive charges and wool with negative charges.

Triboelectric Series
(+) \( \leftarrow \) rabbit skin \ glass \ mica \ wool \ cat fur \ silk \ cotton \ wooden \ amber \ ebonite \ copper \ sulfur \ celluloid \( \rightarrow \) (-)
Whenever one rubs two elements of the series above, the left-hand side elements will give electrons to the elements on the right side.
Electrification by Contact
Whenever an electrified conductor comes into contact with another neutral conductor, the latter is electrified with the same charge present in the former. When the two conductors have the same dimensions and the same shape, after contact, both share the same amount of electric charge.
The electrification scheme by contact between two conductors. a) Initially, we have a body with excess charges and another neutral body. b) When the bodies touch, part of the excess charges go to the body initially neutral. c) As a final result, we have two bodies loaded with the same amount of charges.

Electrification by Induction
When a conductor is electrified by induction, the charging process changes the charges at the electrified body, those charges will have opposite sign to the ones in the inductor.
Scheme of electrification by induction. a) Initially, we have a body with excess of charges and another neutral body. b) Then we connect the body to a reservoir of charges, such as Earth. Since in solids only electrons are "free to move", the Earth gives negative charges to the conductor. c) As a final result, we have two oppositely charged bodies.