(2) The moving-conductor receiver, shown in B,
also contains a permanent magnet, but it operates on the
principle of the electrical meter. The moving conductor
is usually a coil or ribbon of aluminum alloy, attached to
the diaphragm. As the current in the coil varies, the
magnet field around the coil varies. This varying field
reacts with the field of the permanent magnet, causing
the coil to vibrate. The vibrations of the coil are
transferred to the diaphragm, which generates sound
characteristics as the current in the coil. The moving-
conductor receiver is also called the moving-coil
receiver and the dynamic receiver. The dynamic
loudspeaker used in radio receivers is similar to it in
action.
FIGURE 14. Comparison of Operating
Principles of Two Receivers
23.
Magnet-Diaphragm Receiver.
a. Operating principle of magnetic-diaphragm receiver. The operating principle of the magnet-diaphragm
receiver (fig. 15) is based on an elementary principle of magnetism--the ability of a magnet to induce a magnetic field of
opposite polarity in a magnetic material placed near it. Because the induced polarity is opposite, attraction always results
between the magnet and the material. For example, a magnet and an iron nail are attracted to each other.
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