___________________________________________________ Principles of Transmission Lines
Figure 3-13. Leakage in a Transmission Line
ELECTROMAGNETIC FIELDS ABOUT A TRANSMISSION LINE
3-47. The distributed constants of resistance, inductance, and capacitance
are basic properties common to all transmission lines and exist whether or
not any current flow exists. As soon as current flow and voltage exist in a
transmission line, another property becomes quite evident. This is the
presence of an electromagnetic field, or lines of force, about the wires of the
transmission line. The lines of force themselves are not visible; however,
understanding the force that an electron experiences while in the field of
these lines is very important to your understanding of energy transmission.
3-48. There are two kinds of fields; one is associated with voltage and the other
with current. The field associated with voltage is called the electric (E) field. It
exerts a force on any electric charge placed in it. The field associated with
current is called a magnetic (H) field, because it tends to exert a force on any
magnetic pole placed in it. Figure 3-14 illustrates the way in which the E fields
and H fields tend to orient themselves between conductors of a typical two-wire
transmission line. The illustration shows a cross section of the transmission
lines. The E field is represented by solid lines and the H field by dotted lines.
The arrows indicate the direction of the lines of force. Both fields normally
exist together and are spoken of collectively as the electromagnetic field.
Figure 3-14. Fields between Conductors
3-13
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