1. Frictional and
2. Dynamical,
And into—
1. Static, as the opposite of
2. Dynamic electricity.
There are still other definitions or divisions which are in every-day use, such as “vitreous” electricity, “atmospheric” electricity, “resinous” electricity, etc.
Static Electricity.—This is a term employed to define electricity produced by friction. It is properly employed in the sense of a static charge which shows itself by the attraction or repulsion between charged bodies. When static electricity is discharged, it causes more or less of a current, which shows itself by the passage of sparks or a brush discharge; by a peculiar prickling sensation; by an unusual smell due to its chemical effects; by heating the air or other substances in its path; and sometimes in other ways.
Current Electricity.—This may be defined as the quantity of electricity which passes through a conductor in a given time—or, electricity in the act of being discharged, or electricity in motion.
An electric current manifests itself by heating the wire or conductor, by causing a magnetic field around the conductor and by causing chemical changes in a liquid through which it may pass.
Note.—Statics is that branch of mechanics which treats of the forces which keep bodies at rest or in equilibrium. Dynamics treats of bodies in motion. Hence static electricity is electricity at rest. The earth’s great store of electricity is at rest or in equilibrium.
Radiated electricity is electricity in vibration. Where the current oscillates or vibrates back and forth with extreme rapidity, it takes the form of waves which are similar to waves of light.
Positive Electricity.—This term expresses the condition of the point of an electrified body having the higher energy from which it flows to a lower level. The sign which denotes this phase of electric excitement is +; all electricity is either positive or,-, negative.