ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
straight wire is wound around a core, it forms a coil and that
the magnetic field about the core assumes a different shape.
Figure 56, view A, is actually a partial cutaway view showing
the construction of a simple coil. Figure 56, view B, shows a
crosssectional view of the same coil. Notice that the two ends
of the coil are identified x and y.
FIGURE 56. MAGNETIC FIELD PRODUCED BY A CURRENTCARRYING COIL.
When current is passed through the coil, the magnetic field
about each turn of the wire links with the fields of the
adjacent turns (figure 56, view A). The combined influence of
all the turns produces a twopole field similar to that of a
simple bar magnet. One end of this coil is a north pole and the
other end is a south pole.
(1) Polarity of an Electromagnetic Coil. In figure 53 on page
79, we observed that the direction of the magnetic field around
a straight wire depends on the direction of current in that
wire. Thus, a reversal of current in a wire causes a reversal
in the direction of the magnetic field that. is produced. It
follows that a reversal of the current in a coil also causes a
reversal of the twopole magnetic field about the coil.
When the direction of the current in a coil is known, one can
determine the magnetic polarity of the coil by using the LEFT
HAND RULE FOR COILS.
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