Instruments of the siphon recorder type have been made to work both with and without electrification of the ink.
By the surface density of electrification on a conductor is meant the charge per unit of area, or the number of tubes of electric force which spring from unit area of its surface.
Long, the initial source of electrification being a single Daniell cell.
In the next place we must notice that electrification is a measurable magnitude and in electrostatics is estimated in terms of a unit called the electrostatic unit of electric quantity.
Electrostatic voltmeters are also liable to have their indications disturbed by electrification of the glass cover of the instrument; this can be avoided by varnishing the glass with a semi-conducting varnish so as to prevent the location of electrostatic charges on the glass.
Clerk Maxwell demonstrated, however, that all electric charge or electrification of conductors consists simply in the establishment of a physical state in the surrounding insulator or dielectric, which state is variously called electric strain, electric displacement or electric polarization.
To detect electrification it is best to charge the electroscope by induction.
De C. du Fay on the conductivity of some bodies for the electric agency and the dual character of electrification gave rise to the first notions of ., electricity as an imponderable fluid, or non-gravitative subtile matter, of a more refined and penetrating kind than ordinary liquids and gases.
The electrification of the plate is now tested by sifting over it a mixture of flowers of sulphur and red lead.
The first term on the right hand side expresses the energy of the surface electrification of the conductors in the field, and the second the energy of volume density (if any).