In this connection there is also another thing which you will do well to bear in mind. In Fig. [15] you will notice a core (C) and an insulated wire coil (B) wound around it. The current, through the wire (B), as shown by the darts (D), moves in one direction, and the induced current in the core (C) travels in the opposite direction, as shown by the darts (D).
Parallel Wires.—In like manner, if two wires (A, B, Fig. [16]) are parallel with each other, and a current of electricity passes along the wire (A) in one direction, the induced current in the wire (B) will move in the opposite direction.
These fundamental principles should be thoroughly understood and mastered.
CHAPTER IV[ToC]
FRICTIONAL, VOLTAIC OR GALVANIC, AND ELECTRO-MAGNETIC ELECTRICITY
Three Electrical Sources.—It has been found that there are three kinds of electricity, or, to be more accurate, there are three ways to generate it. These will now be described.