The ancient Greeks knew that when a piece of amber is rubbed with wool or fur, it achieves the power of attracting light objects, later on the phenomenon was studied, and the word “electric” after the Greek word “electron” meaning “amber” was used.
The study of electricity may be divided into three classes: magnetism, electrostatics and electrodynamics.
Magnetism is the property of the molecules of iron and certain other substances through which they store energy in the field of force because of the arranged movement of the electrons in their atoms.
Electrostatics is the study of electricity at rest, or static electricity. Examples of this type of electricity are charge on condenser plates. Rubbing glass with silk produces static electricity.
Electrodynamics is the study of electricity in motion, or dynamic electricity. The electricity which flows through wires for light and power purposes is a good example of latter type of electricity.
No one has ever seen an electric current, we only know of the existence of a current by its effects. There are many kinds of current, for example, a direct current (d.c.), an alternating current (a.c.), a pulsating current.