Page:Elementary lectures on electric discharges, waves and impulses, and other transients (Steinmetz 1911).djvu/25

 LECTURE II. THE ELECTRIC FIELD.

The conductor is surrounded by a magnetic field, or a magnetic flux, which is measured by the number of lines of magnetic force Φ. With a single conductor, the lines of magnetic force are concentric circles, as shown in Fig. 8. By the return conductor, the circles